diff --git a/source/source_pw/module_dfpt/test_serial/CMakeLists.txt b/source/source_pw/module_dfpt/test_serial/CMakeLists.txt
index 9c181c46b84..906b63bb92c 100644
--- a/source/source_pw/module_dfpt/test_serial/CMakeLists.txt
+++ b/source/source_pw/module_dfpt/test_serial/CMakeLists.txt
@@ -43,7 +43,7 @@ addtest(
           # (see test/dfpt_test_mocks.cpp).
           ../test/dfpt_test_mocks.cpp
           # Shared serial-side cell/basis/data fixture.
-          dfpt_serial_fixture.cpp)
+          dfpt_test_tool.cpp)
 
 addtest(
   TARGET MODULE_DFPT_rho_serial
@@ -63,7 +63,7 @@ addtest(
           # (see test/dfpt_test_mocks.cpp).
           ../test/dfpt_test_mocks.cpp
           # Shared serial-side cell/basis/data fixture.
-          dfpt_serial_fixture.cpp)
+          dfpt_test_tool.cpp)
 
 addtest(
   TARGET MODULE_DFPT_phon_serial
@@ -92,7 +92,7 @@ addtest(
           # (see test/dfpt_test_mocks.cpp).
           ../test/dfpt_test_mocks.cpp
           # Shared serial-side cell/basis/data fixture.
-          dfpt_serial_fixture.cpp)
+          dfpt_test_tool.cpp)
 
 addtest(
   TARGET MODULE_DFPT_q0_serial
@@ -114,7 +114,7 @@ addtest(
           # (see test/dfpt_test_mocks.cpp).
           ../test/dfpt_test_mocks.cpp
           # Shared serial-side cell/basis/data fixture.
-          dfpt_serial_fixture.cpp)
+          dfpt_test_tool.cpp)
 
 # QE-format dyn writer + the Gamma-first q-ordering validation consumed by
 # the DFPT driver (test_dfpt_write_dyn.cpp matches dfpt_write_dyn.cpp,
@@ -133,7 +133,7 @@ addtest(
           # (see test/dfpt_test_mocks.cpp).
           ../test/dfpt_test_mocks.cpp
           # Shared serial-side cell/basis/data fixture.
-          dfpt_serial_fixture.cpp)
+          dfpt_test_tool.cpp)
 
 # Analytic libxc first-order XC kernel (empty TU without libxc, so the test
 # only exists when the feature is compiled in)
@@ -156,5 +156,5 @@ if(ENABLE_LIBXC)
             # (see test/dfpt_test_mocks.cpp).
             ../test/dfpt_test_mocks.cpp
             # Shared serial-side cell/basis/data fixture.
-            dfpt_serial_fixture.cpp)
+            dfpt_test_tool.cpp)
 endif()
diff --git a/source/source_pw/module_dfpt/test_serial/dfpt_pert_serial_test.cpp b/source/source_pw/module_dfpt/test_serial/dfpt_pert_serial_test.cpp
index a50fa7e9613..76a0aa32142 100644
--- a/source/source_pw/module_dfpt/test_serial/dfpt_pert_serial_test.cpp
+++ b/source/source_pw/module_dfpt/test_serial/dfpt_pert_serial_test.cpp
@@ -11,14 +11,17 @@
 // the real serial initgrids/initparameters/setuptransform path on a shared
 // FFT grid, exactly like the production setup_pwrho/setup_pwwfc sequence.
 
-#include "dfpt_serial_fixture.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_base/constants.h"
 #include "source_base/matrix3.h"
 #include "source_base/vector3.h"
 #include "source_cell/atom_pseudo.h"
 #include "source_cell/atom_spec.h"
-#include "source_cell/qlist.h"
-#include "source_cell/unitcell.h"
 #include "source_psi/psi.h"
 #include "source_pw/module_dfpt/dfpt_pert.h"
 #include "source_cell/stru_fac.h"
@@ -49,17 +52,38 @@
  *   - build_dv under with_u()/u_active()==false (pure-PW DFT+U safety).
  */
 
-class DFPTPertSerialTest : public DFPTSerialBase
+// per-file self-contained fixture (gtest style): owns its objects and
+// calls the dfpt_test free-function utilities
+class DFPTPertSerialTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModulePW::PW_Basis pw_rho_;
+    ModulePW::PW_Basis_K pw_wfc_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+    ModuleBase::Vector3<double> q_cart_;
     Structure_Factor sf_;
     ModuleDFPT::DFPT_Pert pert_;
 
+    // default (k, q): q generic, k = -q so k+q = 0; tau of atom 0
+    const ModuleBase::Vector3<double> k_d_{-0.13, 0.0, -0.07};
+    const ModuleBase::Vector3<double> q_d_{0.13, 0.0, 0.07};
+    const ModuleBase::Vector3<double> tau_{1.1, 2.3, 0.7};
+
     void SetUp() override
     {
-        DFPTSerialBase::SetUp();
+        dfpt_test::setup_cell(ucell_, latvec_);
+        dfpt_test::setup_bases(pw_rho_, pw_wfc_, qlist_, data_, ucell_, k_d_, q_d_, 2, q_cart_);
         pert_.init(ucell_, &pw_rho_, &pw_wfc_, sf_);
     }
+
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
 };
 
 TEST_F(DFPTPertSerialTest, RhoGvecMatchesDistributedGcar)
@@ -100,8 +124,8 @@ TEST_F(DFPTPertSerialTest, DVlocDtauMatchesFiniteDifference)
                 // per bohr of displacement (GS stru_fac phase convention)
                 const double ap = -ModuleBase::TWO_PI * (w * (tau_ + eps * d));
                 const double am = -ModuleBase::TWO_PI * (w * (tau_ - eps * d));
-                const std::complex<double> fd = VlocCoulomb((w * w) * ucell_.tpiba2)
-                                                * (std::polar(1.0, ap) - std::polar(1.0, am)) / (2.0 * eps * lat0_);
+                const std::complex<double> fd = dfpt_test::vloc_coulomb(ucell_.atoms[0].ncpp.zv, ucell_.omega, (w * w) * ucell_.tpiba2)
+                                                * (std::polar(1.0, ap) - std::polar(1.0, am)) / (2.0 * eps * dfpt_test::lat0);
                 EXPECT_NEAR(dv[ig].real(), fd.real(), 1.0e-9);
                 EXPECT_NEAR(dv[ig].imag(), fd.imag(), 1.0e-9);
             }
@@ -120,7 +144,7 @@ TEST_F(DFPTPertSerialTest, ApplyDvConvolutionMatchesAnalyticMatrixElement)
     ASSERT_EQ(dv_recip.size(), static_cast<size_t>(pw_rho_.npw));
     for (int ig = 0; ig < pw_rho_.npw; ++ig)
     {
-        const std::complex<double> expect = AnalyticDVloc(0, pw_rho_.gcar[ig] + q_cart_);
+        const std::complex<double> expect = dfpt_test::analytic_dvloc(ucell_, tau_, 0, pw_rho_.gcar[ig] + q_cart_);
         EXPECT_NEAR(dv_recip[ig].real(), expect.real(), 1.0e-9);
         EXPECT_NEAR(dv_recip[ig].imag(), expect.imag(), 1.0e-9);
     }
@@ -131,16 +155,16 @@ TEST_F(DFPTPertSerialTest, ApplyDvConvolutionMatchesAnalyticMatrixElement)
     int ig_zero = -1, ig_x = -1, ig_y = -1;
     for (int ig = 0; ig < npwk; ++ig)
     {
-        const long long key = GKey(pw_wfc_.getgpluskcar(0, ig) - kc);
-        if (key == FKey(0, 0, 0))
+        const long long key = dfpt_test::gkey(pw_wfc_.getgpluskcar(0, ig) - kc, dfpt_test::cubic_edge);
+        if (key == dfpt_test::fkey(0, 0, 0))
         {
             ig_zero = ig;
         }
-        else if (key == FKey(1, 0, 0))
+        else if (key == dfpt_test::fkey(1, 0, 0))
         {
             ig_x = ig;
         }
-        else if (key == FKey(0, 1, 0))
+        else if (key == dfpt_test::fkey(0, 1, 0))
         {
             ig_y = ig;
         }
@@ -168,9 +192,9 @@ TEST_F(DFPTPertSerialTest, ApplyDvConvolutionMatchesAnalyticMatrixElement)
     for (int igl = 0; igl < kq.get_npwk(); ++igl)
     {
         const ModuleBase::Vector3<double> gpp = kq.get_gcar(igl);
-        const std::complex<double> e0 = AnalyticDVloc(0, gpp + q_cart_);
-        const std::complex<double> e1 = 0.7 * AnalyticDVloc(0, gpp - g1 + q_cart_)
-                                        + std::complex<double>(0.3, 0.2) * AnalyticDVloc(0, gpp - g2 + q_cart_);
+        const std::complex<double> e0 = dfpt_test::analytic_dvloc(ucell_, tau_, 0, gpp + q_cart_);
+        const std::complex<double> e1 = 0.7 * dfpt_test::analytic_dvloc(ucell_, tau_, 0, gpp - g1 + q_cart_)
+                                        + std::complex<double>(0.3, 0.2) * dfpt_test::analytic_dvloc(ucell_, tau_, 0, gpp - g2 + q_cart_);
         EXPECT_NEAR(d0[igl].real(), e0.real(), 1.0e-8);
         EXPECT_NEAR(d0[igl].imag(), e0.imag(), 1.0e-8);
         EXPECT_NEAR(d1[igl].real(), e1.real(), 1.0e-8);
@@ -180,7 +204,7 @@ TEST_F(DFPTPertSerialTest, ApplyDvConvolutionMatchesAnalyticMatrixElement)
 
 TEST_F(DFPTPertSerialTest, BuildVkbL0MatchesIndependentSimpson)
 {
-    MakeNCAtom();
+    dfpt_test::make_nc_atom(ucell_);
     const int npwk = pw_wfc_.npwk[0];
     std::vector<ModuleBase::Vector3<double>> gk(npwk);
     for (int ig = 0; ig < npwk; ++ig)
@@ -245,7 +269,7 @@ TEST_F(DFPTPertSerialTest, BuildVkbL0MatchesIndependentSimpson)
 
 TEST_F(DFPTPertSerialTest, DVnlDtauMatchesOperatorFiniteDifference)
 {
-    MakeNCAtom();
+    dfpt_test::make_nc_atom(ucell_);
     const int npwk = pw_wfc_.npwk[0];
     ModuleDFPT::DFPT_KQ_Basis kq;
     kq.init(&pw_wfc_, &pw_rho_, q_cart_, 0);
@@ -354,7 +378,7 @@ TEST_F(DFPTPertSerialTest, DVnlDtauMatchesOperatorFiniteDifference)
         }
         for (int igl = 0; igl < npwkq; ++igl)
         {
-            fd[igl] /= (2.0 * eps * lat0_);
+            fd[igl] /= (2.0 * eps * dfpt_test::lat0);
             EXPECT_NEAR(dv_psi[b][igl].real(), fd[igl].real(), 1.0e-7);
             EXPECT_NEAR(dv_psi[b][igl].imag(), fd[igl].imag(), 1.0e-7);
         }
@@ -364,7 +388,7 @@ TEST_F(DFPTPertSerialTest, DVnlDtauMatchesOperatorFiniteDifference)
 TEST_F(DFPTPertSerialTest, NonlocalPathRejectsUltrasoft)
 {
     ::testing::FLAGS_gtest_death_test_style = "threadsafe";
-    MakeNCAtom();
+    dfpt_test::make_nc_atom(ucell_);
     ucell_.atoms[0].ncpp.tvanp = true;
     const int npwk = pw_wfc_.npwk[0];
     psi::Psi<std::complex<double>> psi(1, 1, npwk, npwk, true);
diff --git a/source/source_pw/module_dfpt/test_serial/dfpt_serial_fixture.cpp b/source/source_pw/module_dfpt/test_serial/dfpt_serial_fixture.cpp
deleted file mode 100644
index aa8ed639268..00000000000
--- a/source/source_pw/module_dfpt/test_serial/dfpt_serial_fixture.cpp
+++ /dev/null
@@ -1,225 +0,0 @@
-#include "dfpt_serial_fixture.h"
-
-#include "source_base/constants.h"
-
-#include <cmath>
-
-void DFPTSerialBase::SetUp()
-{
-    SetUpCell();
-    SetupBases(k_d_, q_d_, 2);
-}
-
-void DFPTSerialBase::SetUpCell()
-{
-    latvec_ = ModuleBase::Matrix3(a_, 0.0, 0.0, 0.0, a_, 0.0, 0.0, 0.0, a_);
-    ucell_.ntype = 1;
-    ucell_.nat = 1;
-    ucell_.atoms = new Atom[1];
-    ucell_.atoms[0].na = 1;
-    ucell_.atoms[0].tau.resize(1);
-    ucell_.atoms[0].tau[0] = tau_;
-    ucell_.latvec = latvec_;
-    ucell_.GT = latvec_.Inverse();
-    ucell_.G = ucell_.GT.Transpose();
-    ucell_.lat0 = lat0_;
-    ucell_.tpiba = ModuleBase::TWO_PI / lat0_;
-    ucell_.tpiba2 = ucell_.tpiba * ucell_.tpiba;
-    ucell_.omega = a_ * a_ * a_ * lat0_ * lat0_ * lat0_;
-    ucell_.iat2it.resize(1);
-    ucell_.iat2ia.resize(1);
-    ucell_.iat2it[0] = 0;
-    ucell_.iat2ia[0] = 0;
-    MakeCoulombAtom();
-}
-
-void DFPTSerialBase::SetupBases(const ModuleBase::Vector3<double>& k_d,
-                                const ModuleBase::Vector3<double>& q_d,
-                                int nbands)
-{
-    G_ = ucell_.G;
-    pw_rho_.initgrids(lat0_, latvec_, rho_mult_ * ecutwfc_);
-    pw_rho_.initparameters(false, rho_mult_ * ecutwfc_);
-    pw_rho_.fft_bundle.initfftmode(0);
-    pw_rho_.setuptransform();
-    pw_rho_.collect_local_pw();
-
-    const ModuleBase::Vector3<double> klist[1] = {k_d};
-    pw_wfc_.initgrids(lat0_, latvec_, pw_rho_.nx, pw_rho_.ny, pw_rho_.nz);
-    pw_wfc_.initparameters(false, ecutwfc_, 1, klist);
-    pw_wfc_.fft_bundle.initfftmode(0);
-    pw_wfc_.setuptransform();
-    pw_wfc_.collect_local_pw();
-
-    qlist_.nkstot = 1;
-    qlist_.kvec_d.clear();
-    qlist_.kvec_d.push_back(q_d);
-    q_cart_ = q_d * ucell_.G;
-
-    data_.init(&qlist_, 1, nbands, pw_wfc_.npwk_max, pw_rho_.nrxx, 1, 1, nullptr);
-}
-
-void DFPTSerialBase::TearDown()
-{
-    delete[] ucell_.atoms;
-    ucell_.atoms = nullptr;
-}
-
-void DFPTSerialBase::MakeCoulombAtom()
-{
-    Atom& at = ucell_.atoms[0];
-    at.label = "C";
-    at.coulomb_potential = true;
-    at.ncpp.zv = 4.0;
-    at.ncpp.tvanp = false;
-    at.ncpp.has_so = false;
-    at.ncpp.nbeta = 0;
-    at.ncpp.nh = 0;
-    at.ncpp.msh = 0;
-    at.ncpp.kkbeta = 0;
-    at.mass = 12.0;
-}
-
-void DFPTSerialBase::MakeNCAtom()
-{
-    Atom& at = ucell_.atoms[0];
-    at.label = "Si";
-    at.coulomb_potential = false;
-    pseudo& p = at.ncpp;
-    p.zv = 4.0;
-    p.tvanp = false;
-    p.has_so = false;
-    p.nbeta = 2;
-    p.lll = {0, 1};
-    p.nh = 4;
-    p.msh = 121;
-    p.kkbeta = 121;
-    p.r.resize(121);
-    p.rab.resize(121);
-    p.vloc_at.assign(121, 0.0);
-    const double dx = 0.025;
-    for (int i = 0; i < 121; ++i)
-    {
-        p.r[i] = i * dx;
-        p.rab[i] = dx;
-    }
-    p.betar.create(2, 121);
-    for (int i = 0; i < 121; ++i)
-    {
-        const double r = p.r[i];
-        p.betar(0, i) = std::exp(-std::pow(r - 1.0, 2) / (2.0 * 0.3 * 0.3));
-        p.betar(1, i) = std::exp(-std::pow(r - 1.2, 2) / (2.0 * 0.35 * 0.35));
-    }
-    p.dion.create(2, 2);
-    p.dion(0, 0) = 0.8;
-    p.dion(0, 1) = 0.15;
-    p.dion(1, 0) = -0.25;
-    p.dion(1, 1) = 1.1;
-}
-
-void DFPTSerialBase::MakeTwoAtomCell()
-{
-    ucell_.ntype = 2;
-    ucell_.nat = 2;
-    delete[] ucell_.atoms;
-    ucell_.atoms = new Atom[2];
-    ucell_.atoms[0].na = 1;
-    ucell_.atoms[1].na = 1;
-    ucell_.atoms[0].tau.resize(1);
-    ucell_.atoms[1].tau.resize(1);
-    ucell_.atoms[0].tau[0] = ModuleBase::Vector3<double>(0.0, 0.0, 0.0);
-    ucell_.atoms[1].tau[0] = ModuleBase::Vector3<double>(0.25, 0.31, 0.17);
-    for (int it = 0; it < 2; ++it)
-    {
-        Atom& at = ucell_.atoms[it];
-        at.label = (it == 0) ? "A" : "B";
-        at.coulomb_potential = true;
-        at.ncpp.zv = (it == 0) ? 4.0 : 2.0;
-        at.ncpp.tvanp = false;
-        at.ncpp.has_so = false;
-        at.ncpp.nbeta = 0;
-        at.ncpp.nh = 0;
-        at.mass = (it == 0) ? 12.0 : 4.0;
-    }
-    ucell_.iat2it.resize(2);
-    ucell_.iat2ia.resize(2);
-    ucell_.iat2it[0] = 0;
-    ucell_.iat2ia[0] = 0;
-    ucell_.iat2it[1] = 1;
-    ucell_.iat2ia[1] = 0;
-}
-
-void DFPTSerialBase::MakeNlccTwoAtomCell()
-{
-    // start from the symmetric-broken two-atom cell, then upgrade the
-    // second species (the one at the non-origin tau_nlcc_) to an NC
-    // pseudo with a nonlinear core correction
-    MakeTwoAtomCell();
-    Atom& at = ucell_.atoms[1];
-    at.label = "Bc";
-    at.coulomb_potential = false;
-    pseudo& p = at.ncpp;
-    p.zv = 2.0;
-    p.tvanp = false;
-    p.has_so = false;
-    p.nbeta = 0;
-    p.lll = {};
-    p.nh = 0;
-    p.msh = 121;
-    p.kkbeta = 121;
-    p.r.resize(121);
-    p.rab.resize(121);
-    p.vloc_at.assign(121, 0.0);
-    const double dx = 0.025;
-    for (int i = 0; i < 121; ++i)
-    {
-        p.r[i] = i * dx;
-        p.rab[i] = dx;
-    }
-    // Gaussian core charge normalized to the integrated nlcc_core_charge_
-    // (rho_atc carries the 4 pi r^2 measure of the radial grid)
-    const double s2 = nlcc_sigma_ * nlcc_sigma_;
-    double norm = 0.0;
-    for (int i = 0; i < 121; ++i)
-    {
-        const double r = p.r[i];
-        norm += r * r * std::exp(-r * r / (2.0 * s2)) * p.rab[i];
-    }
-    const double amp = nlcc_core_charge_ / (norm * ModuleBase::FOUR_PI);
-    p.rho_atc.resize(121);
-    for (int i = 0; i < 121; ++i)
-    {
-        const double r = p.r[i];
-        p.rho_atc[i] = amp * std::exp(-r * r / (2.0 * s2));
-    }
-    p.nlcc = true;
-}
-
-long long DFPTSerialBase::FKey(int ix, int iy, int iz) const
-{
-    return (static_cast<long long>(ix + 64) * 128 + (iy + 64)) * 128 + (iz + 64);
-}
-
-long long DFPTSerialBase::GKey(const ModuleBase::Vector3<double>& g) const
-{
-    return FKey(static_cast<int>(std::llround(g.x * a_)),
-                static_cast<int>(std::llround(g.y * a_)),
-                static_cast<int>(std::llround(g.z * a_)));
-}
-
-double DFPTSerialBase::VlocCoulomb(double g2_bohr) const
-{
-    return -ucell_.atoms[0].ncpp.zv * ModuleBase::e2 * ModuleBase::FOUR_PI / ucell_.omega / g2_bohr;
-}
-
-std::complex<double> DFPTSerialBase::AnalyticDVloc(int dir, const ModuleBase::Vector3<double>& w) const
-{
-    const double w2 = w * w;
-    if (w2 < 1.0e-12)
-    {
-        return std::complex<double>(0.0, 0.0);
-    }
-    const double arg = -ModuleBase::TWO_PI * (w * tau_);
-    return std::complex<double>(0.0, -1.0) * (ucell_.tpiba * w[dir]) * VlocCoulomb(w2 * ucell_.tpiba2)
-           * std::complex<double>(std::cos(arg), std::sin(arg));
-}
diff --git a/source/source_pw/module_dfpt/test_serial/dfpt_serial_fixture.h b/source/source_pw/module_dfpt/test_serial/dfpt_serial_fixture.h
deleted file mode 100644
index 065ee223fd2..00000000000
--- a/source/source_pw/module_dfpt/test_serial/dfpt_serial_fixture.h
+++ /dev/null
@@ -1,98 +0,0 @@
-#ifndef DFPT_SERIAL_FIXTURE_H
-#define DFPT_SERIAL_FIXTURE_H
-
-#include "source_base/matrix3.h"
-#include "source_base/vector3.h"
-#include "source_basis/module_pw/pw_basis.h"
-#include "source_basis/module_pw/pw_basis_k.h"
-#include "source_cell/qlist.h"
-#include "source_cell/unitcell.h"
-#include "source_pw/module_dfpt/dfpt_pw_data.h"
-
-#include "gtest/gtest.h"
-#include <complex>
-
-// Shared serial-side gtest fixture for the DFPT unit tests
-// (dfpt_pert/rho/phon/q0_serial_test.cpp). Everything runs without
-// __MPI: the plane-wave bases are built through the real serial
-// initgrids/initparameters/setuptransform path on a shared FFT grid,
-// exactly like the production setup_pwrho/setup_pwwfc sequence.
-//
-// All members the fixture touches (UnitCell geometry fields, the
-// Atom/pseudo public data, QList::nkstot / kvec_d and the
-// DFPT_PW_Data::init entry) are public, so the tests include the
-// cell/qlist/dfpt headers normally.
-
-class DFPTSerialBase : public testing::Test
-{
-  protected:
-    const double lat0_ = 1.8897261254578281;
-    const double ecutwfc_ = 2.5; // Ry
-    // rho cutoff inflated to 9x ecutwfc so every Delta = G''-G' of the
-    // convolution lies inside the rho ball and nothing aliases
-    const double rho_mult_ = 9.0;
-    const double a_ = 10.0; // cubic edge in lat0 units
-
-    ModuleBase::Matrix3 latvec_;
-    UnitCell ucell_;
-    ModulePW::PW_Basis pw_rho_;
-    ModulePW::PW_Basis_K pw_wfc_;
-    ModuleCell::QList qlist_;
-    ModuleDFPT::DFPT_PW_Data data_;
-    ModuleBase::Matrix3 G_; // = latvec^-T, the reciprocal builder
-
-    // default (k, q) of the pert/phon/rho fixtures: q is generic and
-    // k = -q so k+q = 0: the k+q ball then stays inside the ground-state
-    // G list (single-k limitation documented in DFPT_KQ_Basis)
-    const ModuleBase::Vector3<double> q_d_{0.13, 0.0, 0.07};
-    const ModuleBase::Vector3<double> k_d_{-0.13, 0.0, -0.07};
-    ModuleBase::Vector3<double> q_cart_;
-    const ModuleBase::Vector3<double> tau_{1.1, 2.3, 0.7}; // lat0 units
-
-    // single-atom Coulomb cell + shared-grid bases at the default (k_d_, q_d_)
-    void SetUp() override;
-    void TearDown() override;
-
-    // cubic single-atom Coulomb cell (iat2it/iat2ia allocated)
-    void SetUpCell();
-
-    // (re)initialize the bases and the shared data wiring for a given
-    // (k, q) pair and band count; SetUp uses the default fixture values
-    void SetupBases(const ModuleBase::Vector3<double>& k_d, const ModuleBase::Vector3<double>& q_d, int nbands);
-
-    void MakeCoulombAtom();
-    void MakeNCAtom();
-
-    /// extend the two-atom cell of MakeTwoAtomCell with a nonlinear core
-    /// correction on the second species: a Gaussian rho_atc of total charge
-    /// nlcc_core_charge_ on the existing radial grid (msh points). The
-    /// atom sits at the non-origin tau_nlcc_ = (0.25, 0.31, 0.17) -- the
-    /// anti-blind-spot position: every structure-factor phase is active,
-    /// so a mirrored phase sign (exp(+iG.tau) instead of the QE addcore
-    /// exp(-iG.tau)) places the response at the wrong site and is caught
-    /// directly by the drhoc-localization test.
-    void MakeNlccTwoAtomCell();
-
-    /// total integrated core charge (in e) of the nlcc Gaussian above
-    static constexpr double nlcc_core_charge_ = 0.24;
-    const ModuleBase::Vector3<double> tau_nlcc_{0.25, 0.31, 0.17}; // lat0 units
-    double nlcc_sigma_ = 1.5; // bohr, grid-resolvable (spacing ~0.63 bohr)
-
-    // reconfigure the cell as a two-atom Z=4/Z=2 crystal breaking all symmetry
-    void MakeTwoAtomCell();
-
-    // key of an integer FFT triple (gcar * a is integral on the cubic cell)
-    long long FKey(int ix, int iy, int iz) const;
-    long long GKey(const ModuleBase::Vector3<double>& g) const;
-
-    // analytic Coulomb local potential (Ry) at |g|^2 in bohr^-2, mirroring
-    // vl_pw.cpp::vloc_coulomb independently of DFPT_Pert::vloc_at_g
-    double VlocCoulomb(double g2_bohr) const;
-
-    // analytic dVloc/dtau_alpha coefficient at displacement vector w (1/lat0);
-    // GS structure-factor convention (stru_fac.cpp): exp(-i 2pi (g.tau)) and
-    // dV/dtau = -i (Delta+q)_alpha tpiba Vloc exp(-i 2pi (Delta+q).tau)
-    std::complex<double> AnalyticDVloc(int dir, const ModuleBase::Vector3<double>& w) const;
-};
-
-#endif // DFPT_SERIAL_FIXTURE_H
diff --git a/source/source_pw/module_dfpt/test_serial/dfpt_test_tool.cpp b/source/source_pw/module_dfpt/test_serial/dfpt_test_tool.cpp
new file mode 100644
index 00000000000..b920996ecd9
--- /dev/null
+++ b/source/source_pw/module_dfpt/test_serial/dfpt_test_tool.cpp
@@ -0,0 +1,259 @@
+// Shared free-function utilities for the DFPT serial unit tests,
+// implementation (see dfpt_test_tool.h). Everything runs without __MPI:
+// the plane-wave bases are built through the real serial
+// initgrids/initparameters/setuptransform path on a shared FFT grid,
+// exactly like the production setup_pwrho/setup_pwwfc sequence.
+
+#include "dfpt_test_tool.h"
+
+#include "source_base/constants.h"
+#include "source_base/matrix3.h"
+#include "source_base/vector3.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/atom_pseudo.h"
+#include "source_cell/atom_spec.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_psi/psi.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
+
+#include <cmath>
+#include <vector>
+
+namespace dfpt_test
+{
+
+// nlcc Gaussian conventions of make_nlcc_two_atom_cell
+constexpr double nlcc_sigma = 1.5;        // bohr, grid-resolvable (spacing ~0.63 bohr)
+constexpr double nlcc_core_charge = 0.24; // e, integrated
+
+void setup_cell(UnitCell& ucell, ModuleBase::Matrix3& latvec)
+{
+    latvec = ModuleBase::Matrix3(cubic_edge, 0.0, 0.0, 0.0, cubic_edge, 0.0, 0.0, 0.0, cubic_edge);
+    ucell.ntype = 1;
+    ucell.nat = 1;
+    ucell.atoms = new Atom[1];
+    ucell.atoms[0].na = 1;
+    ucell.atoms[0].tau.resize(1);
+    ucell.atoms[0].tau[0] = ModuleBase::Vector3<double>(1.1, 2.3, 0.7);
+    ucell.latvec = latvec;
+    ucell.GT = latvec.Inverse();
+    ucell.G = ucell.GT.Transpose();
+    ucell.lat0 = lat0;
+    ucell.tpiba = ModuleBase::TWO_PI / lat0;
+    ucell.tpiba2 = ucell.tpiba * ucell.tpiba;
+    ucell.omega = cubic_edge * cubic_edge * cubic_edge * lat0 * lat0 * lat0;
+    ucell.iat2it.resize(1);
+    ucell.iat2ia.resize(1);
+    ucell.iat2it[0] = 0;
+    ucell.iat2ia[0] = 0;
+    make_coulomb_atom(ucell);
+}
+
+void make_coulomb_atom(UnitCell& ucell)
+{
+    Atom& at = ucell.atoms[0];
+    at.label = "C";
+    at.coulomb_potential = true;
+    at.ncpp.zv = 4.0;
+    at.ncpp.tvanp = false;
+    at.ncpp.has_so = false;
+    at.ncpp.nbeta = 0;
+    at.ncpp.nh = 0;
+    at.ncpp.msh = 0;
+    at.ncpp.kkbeta = 0;
+    at.mass = 12.0;
+}
+
+void make_nc_atom(UnitCell& ucell)
+{
+    Atom& at = ucell.atoms[0];
+    at.label = "Si";
+    at.coulomb_potential = false;
+    pseudo& p = at.ncpp;
+    p.zv = 4.0;
+    p.tvanp = false;
+    p.has_so = false;
+    p.nbeta = 2;
+    p.lll = {0, 1};
+    p.nh = 4;
+    p.msh = 121;
+    p.kkbeta = 121;
+    p.r.resize(121);
+    p.rab.resize(121);
+    p.vloc_at.assign(121, 0.0);
+    const double dx = 0.025;
+    for (int i = 0; i < 121; ++i)
+    {
+        p.r[i] = i * dx;
+        p.rab[i] = dx;
+    }
+    p.betar.create(2, 121);
+    for (int i = 0; i < 121; ++i)
+    {
+        const double r = p.r[i];
+        p.betar(0, i) = std::exp(-std::pow(r - 1.0, 2) / (2.0 * 0.3 * 0.3));
+        p.betar(1, i) = std::exp(-std::pow(r - 1.2, 2) / (2.0 * 0.35 * 0.35));
+    }
+    p.dion.create(2, 2);
+    p.dion(0, 0) = 0.8;
+    p.dion(0, 1) = 0.15;
+    p.dion(1, 0) = -0.25;
+    p.dion(1, 1) = 1.1;
+}
+
+void make_two_atom_cell(UnitCell& ucell)
+{
+    ucell.ntype = 2;
+    ucell.nat = 2;
+    delete[] ucell.atoms;
+    ucell.atoms = new Atom[2];
+    ucell.atoms[0].na = 1;
+    ucell.atoms[1].na = 1;
+    ucell.atoms[0].tau.resize(1);
+    ucell.atoms[1].tau.resize(1);
+    ucell.atoms[0].tau[0] = ModuleBase::Vector3<double>(0.0, 0.0, 0.0);
+    ucell.atoms[1].tau[0] = ModuleBase::Vector3<double>(0.25, 0.31, 0.17);
+    for (int it = 0; it < 2; ++it)
+    {
+        Atom& at = ucell.atoms[it];
+        at.label = (it == 0) ? "A" : "B";
+        at.coulomb_potential = true;
+        at.ncpp.zv = (it == 0) ? 4.0 : 2.0;
+        at.ncpp.tvanp = false;
+        at.ncpp.has_so = false;
+        at.ncpp.nbeta = 0;
+        at.ncpp.nh = 0;
+        at.mass = (it == 0) ? 12.0 : 4.0;
+    }
+    ucell.iat2it.resize(2);
+    ucell.iat2ia.resize(2);
+    ucell.iat2it[0] = 0;
+    ucell.iat2ia[0] = 0;
+    ucell.iat2it[1] = 1;
+    ucell.iat2ia[1] = 0;
+}
+
+void make_nlcc_two_atom_cell(UnitCell& ucell)
+{
+    // start from the symmetry-broken two-atom cell, then upgrade the
+    // second species (the one at the non-origin tau) to an NC pseudo
+    // with a nonlinear core correction
+    make_two_atom_cell(ucell);
+    Atom& at = ucell.atoms[1];
+    at.label = "Bc";
+    at.coulomb_potential = false;
+    pseudo& p = at.ncpp;
+    p.zv = 2.0;
+    p.tvanp = false;
+    p.has_so = false;
+    p.nbeta = 0;
+    p.lll = {};
+    p.nh = 0;
+    p.msh = 121;
+    p.kkbeta = 121;
+    p.r.resize(121);
+    p.rab.resize(121);
+    p.vloc_at.assign(121, 0.0);
+    const double dx = 0.025;
+    for (int i = 0; i < 121; ++i)
+    {
+        p.r[i] = i * dx;
+        p.rab[i] = dx;
+    }
+    // Gaussian core charge normalized to the integrated nlcc_core_charge
+    // (rho_atc carries the 4 pi r^2 measure of the radial grid)
+    const double s2 = nlcc_sigma * nlcc_sigma;
+    double norm = 0.0;
+    for (int i = 0; i < 121; ++i)
+    {
+        const double r = p.r[i];
+        norm += r * r * std::exp(-r * r / (2.0 * s2)) * p.rab[i];
+    }
+    const double amp = nlcc_core_charge / (norm * ModuleBase::FOUR_PI);
+    p.rho_atc.resize(121);
+    for (int i = 0; i < 121; ++i)
+    {
+        const double r = p.r[i];
+        p.rho_atc[i] = amp * std::exp(-r * r / (2.0 * s2));
+    }
+    p.nlcc = true;
+}
+
+void setup_bases(ModulePW::PW_Basis& pw_rho,
+                 ModulePW::PW_Basis_K& pw_wfc,
+                 ModuleCell::QList& qlist,
+                 ModuleDFPT::DFPT_PW_Data& data,
+                 const UnitCell& ucell,
+                 const ModuleBase::Vector3<double>& k_d,
+                 const ModuleBase::Vector3<double>& q_d,
+                 int nbands,
+                 ModuleBase::Vector3<double>& q_cart)
+{
+    // The tool keeps its own five-call assembly chains instead of
+    // calling the production pw::setup_pwrho / setup_pwwfc wrappers
+    // (which also run without __MPI): the tests need rho_mult = 9x
+    // ecutwfc for the DFPT convolution (every Delta = G''-G' must fit
+    // in the rho ball) while production hardcodes 4x ecutwfc; they
+    // re-assemble for arbitrary (k, q) pairs per case, which the
+    // K_Vectors-driven wrapper is not shaped for; and the wrappers
+    // write to the running-log global stream and require a fabricated
+    // Input_para.
+    const ModuleBase::Matrix3& latvec = ucell.latvec;
+    pw_rho.initgrids(lat0, latvec, rho_mult * ecutwfc);
+    pw_rho.initparameters(false, rho_mult * ecutwfc);
+    pw_rho.fft_bundle.initfftmode(0);
+    pw_rho.setuptransform();
+    pw_rho.collect_local_pw();
+
+    const ModuleBase::Vector3<double> klist[1] = {k_d};
+    pw_wfc.initgrids(lat0, latvec, pw_rho.nx, pw_rho.ny, pw_rho.nz);
+    pw_wfc.initparameters(false, ecutwfc, 1, klist);
+    pw_wfc.fft_bundle.initfftmode(0);
+    pw_wfc.setuptransform();
+    pw_wfc.collect_local_pw();
+
+    qlist.nkstot = 1;
+    qlist.kvec_d.clear();
+    qlist.kvec_d.push_back(q_d);
+    q_cart = q_d * ucell.G;
+
+    data.init(&qlist, 1, nbands, pw_wfc.npwk_max, pw_rho.nrxx, 1, 1, nullptr);
+}
+
+double vloc_coulomb(double zv, double omega, double g2_bohr)
+{
+    return -zv * ModuleBase::e2 * ModuleBase::FOUR_PI / omega / g2_bohr;
+}
+
+std::complex<double> analytic_dvloc(const UnitCell& ucell,
+                                    const ModuleBase::Vector3<double>& tau,
+                                    int dir,
+                                    const ModuleBase::Vector3<double>& w)
+{
+    const double w2 = w * w;
+    if (w2 < 1.0e-12)
+    {
+        return std::complex<double>(0.0, 0.0);
+    }
+    const double zv = ucell.atoms[0].ncpp.zv;
+    const double arg = -ModuleBase::TWO_PI * (w * tau);
+    return std::complex<double>(0.0, -1.0) * (ucell.tpiba * w[dir])
+           * vloc_coulomb(zv, ucell.omega, w2 * ucell.tpiba2)
+           * std::complex<double>(std::cos(arg), std::sin(arg));
+}
+
+long long fkey(int ix, int iy, int iz)
+{
+    return (static_cast<long long>(ix + 64) * 128 + (iy + 64)) * 128 + (iz + 64);
+}
+
+long long gkey(const ModuleBase::Vector3<double>& g, double a)
+{
+    return fkey(static_cast<int>(std::llround(g.x * a)),
+                static_cast<int>(std::llround(g.y * a)),
+                static_cast<int>(std::llround(g.z * a)));
+}
+
+} // namespace dfpt_test
diff --git a/source/source_pw/module_dfpt/test_serial/dfpt_test_tool.h b/source/source_pw/module_dfpt/test_serial/dfpt_test_tool.h
new file mode 100644
index 00000000000..6dd78684d93
--- /dev/null
+++ b/source/source_pw/module_dfpt/test_serial/dfpt_test_tool.h
@@ -0,0 +1,100 @@
+#ifndef DFPT_TEST_TOOL_H
+#define DFPT_TEST_TOOL_H
+
+// Shared free-function utilities for the DFPT serial unit tests
+// (module_pw test/test_tool.{h,cpp} pattern): every test file derives
+// its own gtest fixture from ::testing::Test, owns the objects it needs
+// and calls these functions -- there is no shared fixture base class.
+
+#include <complex>
+
+class UnitCell;
+namespace ModuleBase
+{
+class Matrix3;
+template <class T>
+class Vector3;
+}
+namespace ModulePW
+{
+class PW_Basis;
+class PW_Basis_K;
+}
+namespace ModuleCell
+{
+class QList;
+}
+namespace ModuleDFPT
+{
+class DFPT_PW_Data;
+}
+
+namespace dfpt_test
+{
+
+// shared test-world conventions (the fixture values every test agrees on)
+constexpr double lat0 = 1.8897261254578281; // bohr
+constexpr double ecutwfc = 2.5;             // Ry
+// rho cutoff inflated to 9x ecutwfc so every Delta = G''-G' of the
+// convolution lies inside the rho ball and nothing aliases
+constexpr double rho_mult = 9.0;
+constexpr double cubic_edge = 10.0; // cubic cell edge in lat0 units
+
+// Build the cubic single-atom cell (latvec / G / GT / tpiba / omega and
+// the iat2it / iat2ia wiring; the atom itself is Coulomb flavor until a
+// make_*_atom call replaces it).
+void setup_cell(UnitCell& ucell, ModuleBase::Matrix3& latvec);
+
+// Reconfigure the cell's single atom as a bare Coulomb Z=4 atom at tau.
+void make_coulomb_atom(UnitCell& ucell);
+
+// Reconfigure the cell's single atom as a norm-conserving pseudo atom
+// (analytic Bessel projectors, no nlcc).
+void make_nc_atom(UnitCell& ucell);
+
+// Reconfigure the cell as a two-atom Z=4/Z=2 crystal breaking all
+// symmetry (masses 12/4), the second atom at the anti-blind-spot tau
+// (0.25, 0.31, 0.17).
+void make_two_atom_cell(UnitCell& ucell);
+
+// Extend the two-atom cell with a nonlinear core correction on the
+// second species: a Gaussian rho_atc of total charge 0.24 e at the
+// non-origin tau (0.25, 0.31, 0.17).
+void make_nlcc_two_atom_cell(UnitCell& ucell);
+
+// Assemble the shared rho/wfc bases for a (k, q) pair and bind the q
+// list and the data object: the rho basis at rho_mult * ecutwfc, the
+// wfc basis on the rho FFT box with the k list, the q list holding the
+// single q, and q_cart = q_frac * ucell.G. Convention: k defaults to -q
+// so the k+q ball stays inside the ground-state G list.
+void setup_bases(ModulePW::PW_Basis& pw_rho,
+                 ModulePW::PW_Basis_K& pw_wfc,
+                 ModuleCell::QList& qlist,
+                 ModuleDFPT::DFPT_PW_Data& data,
+                 const UnitCell& ucell,
+                 const ModuleBase::Vector3<double>& k_d,
+                 const ModuleBase::Vector3<double>& q_d,
+                 int nbands,
+                 ModuleBase::Vector3<double>& q_cart);
+
+// Analytic Coulomb local potential (Ry) at g2_bohr (bohr^-2) for valence
+// zv in cell volume omega, mirroring
+// vl_pw.cpp::vloc_coulomb independently of DFPT_Pert::vloc_at_g.
+double vloc_coulomb(double zv, double omega, double g2_bohr);
+
+// Analytic dVloc/dtau_alpha coefficient at displacement vector w
+// (1/lat0): dV/dtau = -i (w)_alpha tpiba Vloc exp(-i 2pi w.tau) with the
+// GS structure-factor phase convention.
+std::complex<double> analytic_dvloc(const UnitCell& ucell,
+                                    const ModuleBase::Vector3<double>& tau,
+                                    int dir,
+                                    const ModuleBase::Vector3<double>& w);
+
+// Integer FFT triple key (ix, iy, iz) on the cubic cell.
+long long fkey(int ix, int iy, int iz);
+// Key of g on the cubic cell (gcar * a is integral).
+long long gkey(const ModuleBase::Vector3<double>& g, double a);
+
+} // namespace dfpt_test
+
+#endif // DFPT_TEST_TOOL_H
diff --git a/source/source_pw/module_dfpt/test_serial/test_dfpt_phon.cpp b/source/source_pw/module_dfpt/test_serial/test_dfpt_phon.cpp
index 62780636479..ca564697d05 100644
--- a/source/source_pw/module_dfpt/test_serial/test_dfpt_phon.cpp
+++ b/source/source_pw/module_dfpt/test_serial/test_dfpt_phon.cpp
@@ -3,33 +3,60 @@
 // form, the Gamma check_sum_rule, the LO-TO direction normalization, the
 // corrected-frequency diagonalization, and the output format regression.
 
-#include "dfpt_serial_fixture.h"
-#include "source_base/constants.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_base/complexmatrix.h"
+#include "source_base/constants.h"
 #include "source_cell/stru_fac.h"
+#include "source_psi/psi.h"
+#include "source_pw/module_dfpt/dfpt_kq_basis.h"
 #include "source_pw/module_dfpt/dfpt_pert.h"
 #include "source_pw/module_dfpt/dfpt_phon.h"
 
-// per-file fixture (self-contained, gtest style): only the members and
-// helpers this file's cases need
-class DFPTPhonSerialTest : public DFPTSerialBase
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+// per-file self-contained fixture (gtest style): owns its objects and
+// calls the dfpt_test free-function utilities
+class DFPTPhonSerialTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModulePW::PW_Basis pw_rho_;
+    ModulePW::PW_Basis_K pw_wfc_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+    ModuleBase::Vector3<double> q_cart_;
     Structure_Factor sf_;
     ModuleDFPT::DFPT_Pert pert_;
     ModuleDFPT::DFPT_Phon phon_;
 
+    // default (k, q) of this file: q is generic and k = -q so k+q = 0
+    const ModuleBase::Vector3<double> k_d_{-0.13, 0.0, -0.07};
+    const ModuleBase::Vector3<double> q_d_{0.13, 0.0, 0.07};
+
     void SetUp() override
     {
-        DFPTSerialBase::SetUp();
+        dfpt_test::setup_cell(ucell_, latvec_);
         SetupPhon(k_d_, q_d_);
     }
 
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
+
     // (re)initialize the bases and the pert/phon wiring for a given (k, q)
     // pair; SetUp uses the default fixture values
     void SetupPhon(const ModuleBase::Vector3<double>& k_d, const ModuleBase::Vector3<double>& q_d)
     {
-        SetupBases(k_d, q_d, 2);
+        dfpt_test::setup_bases(pw_rho_, pw_wfc_, qlist_, data_, ucell_, k_d, q_d, 2, q_cart_);
         pert_.init(ucell_, &pw_rho_, &pw_wfc_, sf_);
         phon_.init(ucell_, &pw_rho_, &pert_);
     }
@@ -59,12 +86,9 @@ class DFPTPhonSerialTest : public DFPTSerialBase
         z2(0, 0) = z2(1, 1) = z2(2, 2) = 2.0;
         data_.set_born(0, z1);
         data_.set_born(1, z2);
-        MakeTwoAtomCell();
+        dfpt_test::make_two_atom_cell(ucell_);
     }
 };
-
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
 #include <algorithm>
 #include <cmath>
 #include <complex>
@@ -76,7 +100,7 @@ TEST_F(DFPTPhonSerialTest, DiagonalizeKnownMatrix)
     // 2-atom layout so nat3 = 6. Hermitian blocks with known closed-form
     // spectra: [[a, c], [conj(c), b]] has eigenvalues (a+b)/2
     // +- sqrt(((a-b)/2)^2 + |c|^2)
-    MakeTwoAtomCell();
+    dfpt_test::make_two_atom_cell(ucell_);
     const double lam[6] = {0.04, 0.09, 0.16, -0.02, 0.01, 0.1225}; // Ry/bohr^2/amu
     ModuleBase::ComplexMatrix dyn(6, 6, true);
     for (int i = 0; i < 6; ++i)
diff --git a/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_asr.cpp b/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_asr.cpp
index 41f431c6278..202c0ce5b87 100644
--- a/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_asr.cpp
+++ b/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_asr.cpp
@@ -4,43 +4,68 @@
 // sum rule, ASR+LO-TO interplay, and the directional-cancellation and
 // cross-Cartesian regressions.
 
-#include "dfpt_serial_fixture.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_base/complexmatrix.h"
 #include "source_cell/stru_fac.h"
+#include "source_psi/psi.h"
+#include "source_pw/module_dfpt/dfpt_kq_basis.h"
 #include "source_pw/module_dfpt/dfpt_pert.h"
 #include "source_pw/module_dfpt/dfpt_phon.h"
 
-// per-file fixture (self-contained, gtest style): only the members and
-// helpers this file's cases need
-class DFPTPhonSerialTest : public DFPTSerialBase
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include <algorithm>
+#include <cmath>
+#include <complex>
+#include <vector>
+
+// per-file self-contained fixture (gtest style): owns its objects and
+// calls the dfpt_test free-function utilities
+class DFPTPhonSerialTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModulePW::PW_Basis pw_rho_;
+    ModulePW::PW_Basis_K pw_wfc_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+    ModuleBase::Vector3<double> q_cart_;
     Structure_Factor sf_;
     ModuleDFPT::DFPT_Pert pert_;
     ModuleDFPT::DFPT_Phon phon_;
 
+    // default (k, q) of this file: q is generic and k = -q so k+q = 0
+    const ModuleBase::Vector3<double> k_d_{-0.13, 0.0, -0.07};
+    const ModuleBase::Vector3<double> q_d_{0.13, 0.0, 0.07};
+
     void SetUp() override
     {
-        DFPTSerialBase::SetUp();
+        dfpt_test::setup_cell(ucell_, latvec_);
         SetupPhon(k_d_, q_d_);
     }
 
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
+
     // (re)initialize the bases and the pert/phon wiring for a given (k, q)
     // pair; SetUp uses the default fixture values
     void SetupPhon(const ModuleBase::Vector3<double>& k_d, const ModuleBase::Vector3<double>& q_d)
     {
-        SetupBases(k_d, q_d, 2);
+        dfpt_test::setup_bases(pw_rho_, pw_wfc_, qlist_, data_, ucell_, k_d, q_d, 2, q_cart_);
         pert_.init(ucell_, &pw_rho_, &pw_wfc_, sf_);
         phon_.init(ucell_, &pw_rho_, &pert_);
     }
 };
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
-#include <algorithm>
-#include <cmath>
-#include <complex>
-#include <vector>
 
 namespace
 {
@@ -90,7 +115,7 @@ ModuleBase::ComplexMatrix make_violating_dyn()
 
 TEST_F(DFPTPhonSerialTest, AsrSimpleZeroesRowSums)
 {
-    MakeTwoAtomCell();
+    dfpt_test::make_two_atom_cell(ucell_);
     // rewire the q list to Gamma (the fixture default q is not 0)
     SetupPhon(k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0));
     const ModuleBase::ComplexMatrix dyn0 = make_violating_dyn();
@@ -113,7 +138,7 @@ TEST_F(DFPTPhonSerialTest, AsrSimpleZeroesRowSums)
 
 TEST_F(DFPTPhonSerialTest, AsrCrystalZeroesRowSumsExactlyAndProjectsAcousticToZero)
 {
-    MakeTwoAtomCell();
+    dfpt_test::make_two_atom_cell(ucell_);
     // rewire the q list to Gamma (the fixture default q is not 0)
     SetupPhon(k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0));
     data_.set_dynmat(0, make_violating_dyn());
@@ -144,7 +169,7 @@ TEST_F(DFPTPhonSerialTest, AsrCrystalZeroesRowSumsExactlyAndProjectsAcousticToZe
 
 TEST_F(DFPTPhonSerialTest, AsrCrystalKeepsEquivalentAtomsEquivalent)
 {
-    MakeTwoAtomCell();
+    dfpt_test::make_two_atom_cell(ucell_);
     // symmetry-equivalent atoms carry equal masses; make the two fixture
     // species mass-equal so the equivalence assertion is meaningful
     ucell_.atoms[1].mass = ucell_.atoms[0].mass;
@@ -177,7 +202,7 @@ TEST_F(DFPTPhonSerialTest, AsrCrystalKeepsEquivalentAtomsEquivalent)
 
 TEST_F(DFPTPhonSerialTest, AsrCrystalCorrectsBornChargeSumRule)
 {
-    MakeTwoAtomCell();
+    dfpt_test::make_two_atom_cell(ucell_);
     // rewire the q list to Gamma (the fixture default q is not 0)
     SetupPhon(k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0));
     data_.set_dynmat(0, make_violating_dyn());
@@ -211,7 +236,7 @@ TEST_F(DFPTPhonSerialTest, AsrCrystalPlusLotoKeepsAcousticExactlyZero)
     // the physical acoustic subspace only through sum_a Z*_a = 0 -- mixes
     // into the projected null space and lifts one acoustic frequency (the
     // bn_cubic Gamma run showed +36 cm^-1 before the fix)
-    MakeTwoAtomCell(); // masses 12 / 4: unequal, the trigger
+    dfpt_test::make_two_atom_cell(ucell_); // masses 12 / 4: unequal, the trigger
     SetupPhon(k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0));
     data_.set_dynmat(0, make_violating_dyn());
     ModuleBase::matrix eps(3, 3, true);
@@ -245,7 +270,7 @@ TEST_F(DFPTPhonSerialTest, AsrDirectionalCancellationDetected)
     // regression of the audit-metric fix: the block [[1,-1,0],[-1,1,0]]
     // has zero row sums (sum over ALL columns) but a NONZERO per-direction
     // residual D*t_x; the audit and apply_asr report must not miss it
-    MakeTwoAtomCell();
+    dfpt_test::make_two_atom_cell(ucell_);
     SetupPhon(k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0));
     ModuleBase::ComplexMatrix dyn(6, 6, true);
     // atom0 self-block with the cancellation pattern
@@ -280,7 +305,7 @@ TEST_F(DFPTPhonSerialTest, AsrSimpleCrossCartesianRegression)
     // Hermitian onsite-only fix; simple must still produce a final matrix
     // that is Hermitian, satisfies all three translation constraints
     // exactly, and has a real diagonal
-    MakeTwoAtomCell(); // masses 12/4 (unequal)
+    dfpt_test::make_two_atom_cell(ucell_); // masses 12/4 (unequal)
     SetupPhon(k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0));
     ModuleBase::ComplexMatrix dyn(6, 6, true);
     const double delta = 0.07;
diff --git a/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_elec.cpp b/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_elec.cpp
index 766544a60eb..ec9864418e9 100644
--- a/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_elec.cpp
+++ b/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_elec.cpp
@@ -6,7 +6,12 @@
 // = 1 keeps only the G=0 harmonic); the dpsi slot is restored after the
 // accumulation. Plus the nlcc kernel fill-semantics regression.
 
-#include "dfpt_serial_fixture.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_base/complexmatrix.h"
 #include "source_cell/stru_fac.h"
 #include "source_psi/psi.h"
@@ -17,26 +22,46 @@
 // only NlccDirectTermsFillSemantics instantiates DFPT_Rho
 #include "source_pw/module_dfpt/dfpt_rho.h"
 
-// per-file fixture (self-contained, gtest style): only the members and
-// helpers this file's cases need
-class DFPTPhonSerialTest : public DFPTSerialBase
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+// per-file self-contained fixture (gtest style): owns its objects and
+// calls the dfpt_test free-function utilities
+class DFPTPhonSerialTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModulePW::PW_Basis pw_rho_;
+    ModulePW::PW_Basis_K pw_wfc_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+    ModuleBase::Vector3<double> q_cart_;
     Structure_Factor sf_;
     ModuleDFPT::DFPT_Pert pert_;
     ModuleDFPT::DFPT_Phon phon_;
 
+    // default (k, q) of this file: q is generic and k = -q so k+q = 0
+    const ModuleBase::Vector3<double> k_d_{-0.13, 0.0, -0.07};
+    const ModuleBase::Vector3<double> q_d_{0.13, 0.0, 0.07};
+
     void SetUp() override
     {
-        DFPTSerialBase::SetUp();
+        dfpt_test::setup_cell(ucell_, latvec_);
         SetupPhon(k_d_, q_d_);
     }
 
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
+
     // (re)initialize the bases and the pert/phon wiring for a given (k, q)
     // pair; SetUp uses the default fixture values
     void SetupPhon(const ModuleBase::Vector3<double>& k_d, const ModuleBase::Vector3<double>& q_d)
     {
-        SetupBases(k_d, q_d, 2);
+        dfpt_test::setup_bases(pw_rho_, pw_wfc_, qlist_, data_, ucell_, k_d, q_d, 2, q_cart_);
         pert_.init(ucell_, &pw_rho_, &pw_wfc_, sf_);
         phon_.init(ucell_, &pw_rho_, &pert_);
     }
@@ -85,23 +110,23 @@ class DFPTPhonSerialTest : public DFPTSerialBase
                                            const std::vector<std::complex<double>>& dpsi_inj,
                                            int adir) const
     {
+        // tau of the fixture cell's atom 0 (lat0-cartesian units)
+        const ModuleBase::Vector3<double> tau(1.1, 2.3, 0.7);
         std::complex<double> cross(0.0, 0.0);
         for (int igl = 0; igl < kq.get_npwk(); ++igl)
         {
             const ModuleBase::Vector3<double> gpp = kq.get_gpluskq(igl);
             for (size_t ic = 0; ic < psi_coef.size(); ++ic)
             {
-                // AnalyticDVloc returns 0 at w = 0 (dVloc drop)
+                // dfpt_test::analytic_dvloc returns 0 at w = 0 (dVloc drop)
                 cross += psi_coef[ic] * std::conj(dpsi_inj[igl])
-                         * AnalyticDVloc(adir, gpp - psi_gcart[ic] + q_cart_);
+                         * dfpt_test::analytic_dvloc(ucell_, tau, adir, gpp - psi_gcart[ic] + q_cart_);
             }
         }
         return cross;
     }
 };
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
 #include <cmath>
 #include <complex>
 #include <vector>
@@ -284,9 +309,10 @@ TEST_F(DFPTPhonSerialTest, AccumulateElectronD2CommensurateQ)
                     {
                         continue;
                     }
-                    const double arg = -ModuleBase::TWO_PI * (g * tau_);
+                    const ModuleBase::Vector3<double> tau(1.1, 2.3, 0.7);
+                    const double arg = -ModuleBase::TWO_PI * (g * tau);
                     const std::complex<double> kterm = -(ucell_.tpiba * g[adir]) * (ucell_.tpiba * g[1])
-                                                       * VlocCoulomb(g2 * ucell_.tpiba2)
+                                                       * dfpt_test::vloc_coulomb(ucell_.atoms[0].ncpp.zv, ucell_.omega, g2 * ucell_.tpiba2)
                                                        * std::complex<double>(std::cos(arg), std::sin(arg));
                     d2elem += std::conj(ccoef[i]) * ccoef[j] * kterm;
                 }
@@ -315,11 +341,11 @@ TEST_F(DFPTPhonSerialTest, AccumulateElectronD2CommensurateQ)
 // ---------------------------------------------------------------------------
 TEST_F(DFPTPhonSerialTest, NlccDirectTermsFillSemantics)
 {
-    MakeNlccTwoAtomCell();
+    dfpt_test::make_nlcc_two_atom_cell(ucell_);
     SetupPhon(k_d_, q_d_);
 
     ModuleDFPT::DFPT_Rho rho;
-    rho.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, G_, std::string("rho_plain"), 0.4, 1.0, 8});
+    rho.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, ucell_.G, std::string("rho_plain"), 0.4, 1.0, 8});
     phon_.set_rho(&rho);
 
     const int nrxx = pw_rho_.nrxx;
diff --git a/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_ewald.cpp b/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_ewald.cpp
index 1b5d8aced01..6a173becff3 100644
--- a/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_ewald.cpp
+++ b/source/source_pw/module_dfpt/test_serial/test_dfpt_phon_ewald.cpp
@@ -5,50 +5,75 @@
 // against a direct (unscreened) lattice Hessian sum at a generic
 // incommensurate q where the dipole sum is oscillation-screened.
 
-#include "dfpt_serial_fixture.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_base/complexmatrix.h"
 #include "source_cell/stru_fac.h"
+#include "source_psi/psi.h"
+#include "source_pw/module_dfpt/dfpt_kq_basis.h"
 #include "source_pw/module_dfpt/dfpt_pert.h"
 #include "source_pw/module_dfpt/dfpt_phon.h"
 
-// per-file fixture (self-contained, gtest style): only the members and
-// helpers this file's cases need
-class DFPTPhonSerialTest : public DFPTSerialBase
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include <algorithm>
+#include <cmath>
+#include <complex>
+#include <vector>
+
+// per-file self-contained fixture (gtest style): owns its objects and
+// calls the dfpt_test free-function utilities
+class DFPTPhonSerialTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModulePW::PW_Basis pw_rho_;
+    ModulePW::PW_Basis_K pw_wfc_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+    ModuleBase::Vector3<double> q_cart_;
     Structure_Factor sf_;
     ModuleDFPT::DFPT_Pert pert_;
     ModuleDFPT::DFPT_Phon phon_;
 
+    // default (k, q) of this file: q is generic and k = -q so k+q = 0
+    const ModuleBase::Vector3<double> k_d_{-0.13, 0.0, -0.07};
+    const ModuleBase::Vector3<double> q_d_{0.13, 0.0, 0.07};
+
     void SetUp() override
     {
-        DFPTSerialBase::SetUp();
+        dfpt_test::setup_cell(ucell_, latvec_);
         SetupPhon(k_d_, q_d_);
     }
 
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
+
     // (re)initialize the bases and the pert/phon wiring for a given (k, q)
     // pair; SetUp uses the default fixture values
     void SetupPhon(const ModuleBase::Vector3<double>& k_d, const ModuleBase::Vector3<double>& q_d)
     {
-        SetupBases(k_d, q_d, 2);
+        dfpt_test::setup_bases(pw_rho_, pw_wfc_, qlist_, data_, ucell_, k_d, q_d, 2, q_cart_);
         pert_.init(ucell_, &pw_rho_, &pw_wfc_, sf_);
         phon_.init(ucell_, &pw_rho_, &pert_);
     }
 };
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
-#include <algorithm>
-#include <cmath>
-#include <complex>
-#include <vector>
 
 TEST_F(DFPTPhonSerialTest, IonIonAcousticSumRuleGamma)
 {
     // a two-atom cell with different charges/masses breaks every symmetry:
     // the Gamma acoustic sum rule is then a razor for the Ewald balance
     // (G part + real part + Gaussian self term)
-    MakeTwoAtomCell();
+    dfpt_test::make_two_atom_cell(ucell_);
     ModuleBase::ComplexMatrix dyn(6, 6, true);
     phon_.ion_ion(ModuleBase::Vector3<double>(0.0, 0.0, 0.0), dyn);
 
@@ -86,7 +111,7 @@ TEST_F(DFPTPhonSerialTest, IonIonAcousticSumRuleGamma)
 TEST_F(DFPTPhonSerialTest, IonIonGammaAcousticZeroModes)
 {
     // same two-atom cell: three acoustic eigenvalues vanish at Gamma
-    MakeTwoAtomCell();
+    dfpt_test::make_two_atom_cell(ucell_);
     ModuleBase::ComplexMatrix dyn(6, 6, true);
     phon_.ion_ion(ModuleBase::Vector3<double>(0.0, 0.0, 0.0), dyn);
     data_.set_dynmat(0, dyn);
@@ -114,7 +139,7 @@ TEST_F(DFPTPhonSerialTest, IonIonGenericQVsDirectSum)
     // two-atom cell at an incommensurate q: the Ewald result must agree
     // with a direct (unscreened) dipole-Hessian lattice sum, whose shell
     // oscillation e^{i q l} makes it convergent
-    MakeTwoAtomCell();
+    dfpt_test::make_two_atom_cell(ucell_);
     const ModuleBase::Vector3<double> tau1(0.0, 0.0, 0.0);
     const ModuleBase::Vector3<double> tau2(0.25, 0.31, 0.17);
     const double z[2] = {4.0, 2.0};
@@ -154,9 +179,9 @@ TEST_F(DFPTPhonSerialTest, IonIonGenericQVsDirectSum)
                         {
                             continue;
                         }
-                        const ModuleBase::Vector3<double> r((n1 * a_ + dt.x) * lat0_,
-                                                            (n2 * a_ + dt.y) * lat0_,
-                                                            (n3 * a_ + dt.z) * lat0_);
+                        const ModuleBase::Vector3<double> r((n1 * dfpt_test::cubic_edge + dt.x) * dfpt_test::lat0,
+                                                            (n2 * dfpt_test::cubic_edge + dt.y) * dfpt_test::lat0,
+                                                            (n3 * dfpt_test::cubic_edge + dt.z) * dfpt_test::lat0);
                         const double r2 = r * r;
                         const double r5 = r2 * r2 * std::sqrt(r2);
                         const double ph = ModuleBase::TWO_PI * (q_d_.x * n1 + q_d_.y * n2 + q_d_.z * n3);
diff --git a/source/source_pw/module_dfpt/test_serial/test_dfpt_q0.cpp b/source/source_pw/module_dfpt/test_serial/test_dfpt_q0.cpp
index b1718be4e86..e8fa544bad1 100644
--- a/source/source_pw/module_dfpt/test_serial/test_dfpt_q0.cpp
+++ b/source/source_pw/module_dfpt/test_serial/test_dfpt_q0.cpp
@@ -4,25 +4,38 @@
 // closed-form screened-leg product with the dpsi-slot sentinel), and the
 // build_stars + rotate_tensor cyclic-group regression.
 
-#include "dfpt_serial_fixture.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
 #include "source_base/constants.h"
 #include "source_base/matrix.h"
 #include "source_base/matrix3.h"
 #include "source_base/vector3.h"
 #include "source_cell/atom_pseudo.h"
 #include "source_cell/atom_spec.h"
-#include "source_cell/qlist.h"
-#include "source_cell/unitcell.h"
 #include "source_cell/stru_fac.h"
 #include "source_psi/psi.h"
 #include "source_pw/module_dfpt/dfpt_pert.h"
 #include "source_pw/module_dfpt/dfpt_q0.h"
 
-// per-file fixture (self-contained, gtest style): this fixture is
-// Gamma-only (k_d_ shadows the generic default k of the base)
-class DFPTQ0SerialTest : public DFPTSerialBase
+// per-file self-contained fixture (gtest style): owns its objects and
+// calls the dfpt_test free-function utilities; Gamma-only
+class DFPTQ0SerialTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModulePW::PW_Basis pw_rho_;
+    ModulePW::PW_Basis_K pw_wfc_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+    ModuleBase::Vector3<double> q_cart_;
     Structure_Factor sf_;
     ModuleDFPT::DFPT_Pert pert_;
     ModuleDFPT::DFPT_Q0 q0_;
@@ -32,12 +45,19 @@ class DFPTQ0SerialTest : public DFPTSerialBase
 
     void SetUp() override
     {
-        SetUpCell();
-        SetupBases(k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0), 4);
+        dfpt_test::setup_cell(ucell_, latvec_);
+        dfpt_test::setup_bases(pw_rho_, pw_wfc_, qlist_, data_, ucell_,
+                               k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0), 4, q_cart_);
         pert_.init(ucell_, &pw_rho_, &pw_wfc_, sf_);
         q0_.init(ucell_, &pw_rho_, &pw_wfc_, &pert_);
     }
 
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
+
     // wfc-basis index of the reciprocal vector (ix, iy, iz)/a at Gamma
     int IgOf(int ix, int iy, int iz) const
     {
@@ -45,7 +65,9 @@ class DFPTQ0SerialTest : public DFPTSerialBase
         for (int ig = 0; ig < npwk; ++ig)
         {
             const ModuleBase::Vector3<double> g = pw_wfc_.getgpluskcar(0, ig);
-            if (std::llround(g.x * a_) == ix && std::llround(g.y * a_) == iy && std::llround(g.z * a_) == iz)
+            if (std::llround(g.x * dfpt_test::cubic_edge) == ix
+                && std::llround(g.y * dfpt_test::cubic_edge) == iy
+                && std::llround(g.z * dfpt_test::cubic_edge) == iz)
             {
                 return ig;
             }
@@ -54,15 +76,13 @@ class DFPTQ0SerialTest : public DFPTSerialBase
     }
 };
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
 #include <cmath>
 #include <complex>
 #include <vector>
 
 TEST_F(DFPTQ0SerialTest, BuildVkbDkMatchesFiniteDifference)
 {
-    MakeNCAtom();
+    dfpt_test::make_nc_atom(ucell_);
     // generic shifted list without any |g| = 0 entry (the direction chain is
     // singular at the origin for l >= 1 rows)
     const int ng = 8;
@@ -270,7 +290,7 @@ TEST_F(DFPTQ0SerialTest, StarRotationCyclicGroup)
     for (int i = 0; i < 3; ++i)
     {
         ucell_.atoms[0].taud[i] = ModuleBase::Vector3<double>(t0[i], t0[(i + 1) % 3], t0[(i + 2) % 3]);
-        ucell_.atoms[0].tau[i] = ucell_.atoms[0].taud[i] * a_;
+        ucell_.atoms[0].tau[i] = ucell_.atoms[0].taud[i] * dfpt_test::cubic_edge;
     }
     ucell_.iat2it.resize(3);
     ucell_.iat2ia.resize(3);
@@ -298,8 +318,8 @@ TEST_F(DFPTQ0SerialTest, StarRotationCyclicGroup)
     // single reduced k point (1/4,0,0) on its own wfc basis
     ModulePW::PW_Basis_K kwfc;
     const ModuleBase::Vector3<double> klist[1] = {ModuleBase::Vector3<double>(0.25, 0.0, 0.0)};
-    kwfc.initgrids(lat0_, latvec_, pw_rho_.nx, pw_rho_.ny, pw_rho_.nz);
-    kwfc.initparameters(false, ecutwfc_, 1, klist);
+    kwfc.initgrids(dfpt_test::lat0, latvec_, pw_rho_.nx, pw_rho_.ny, pw_rho_.nz);
+    kwfc.initparameters(false, dfpt_test::ecutwfc, 1, klist);
     kwfc.fft_bundle.initfftmode(0);
     kwfc.setuptransform();
     kwfc.collect_local_pw();
diff --git a/source/source_pw/module_dfpt/test_serial/test_dfpt_q0_pos.cpp b/source/source_pw/module_dfpt/test_serial/test_dfpt_q0_pos.cpp
index ad4ab19fca3..11999393787 100644
--- a/source/source_pw/module_dfpt/test_serial/test_dfpt_q0_pos.cpp
+++ b/source/source_pw/module_dfpt/test_serial/test_dfpt_q0_pos.cpp
@@ -5,25 +5,38 @@
 // (exactly degenerate pairs are skipped); the nonlocal contraction
 // against an operator finite difference of <u_m|V_nl(k)|u_n>.
 
-#include "dfpt_serial_fixture.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
 #include "source_base/constants.h"
 #include "source_base/matrix.h"
 #include "source_base/matrix3.h"
 #include "source_base/vector3.h"
 #include "source_cell/atom_pseudo.h"
 #include "source_cell/atom_spec.h"
-#include "source_cell/qlist.h"
-#include "source_cell/unitcell.h"
 #include "source_cell/stru_fac.h"
 #include "source_psi/psi.h"
 #include "source_pw/module_dfpt/dfpt_pert.h"
 #include "source_pw/module_dfpt/dfpt_q0.h"
 
-// per-file fixture (self-contained, gtest style): this fixture is
-// Gamma-only (k_d_ shadows the generic default k of the base)
-class DFPTQ0SerialTest : public DFPTSerialBase
+// per-file self-contained fixture (gtest style): owns its objects and
+// calls the dfpt_test free-function utilities; Gamma-only
+class DFPTQ0SerialTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModulePW::PW_Basis pw_rho_;
+    ModulePW::PW_Basis_K pw_wfc_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+    ModuleBase::Vector3<double> q_cart_;
     Structure_Factor sf_;
     ModuleDFPT::DFPT_Pert pert_;
     ModuleDFPT::DFPT_Q0 q0_;
@@ -34,12 +47,19 @@ class DFPTQ0SerialTest : public DFPTSerialBase
 
     void SetUp() override
     {
-        SetUpCell();
-        SetupBases(k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0), 4);
+        dfpt_test::setup_cell(ucell_, latvec_);
+        dfpt_test::setup_bases(pw_rho_, pw_wfc_, qlist_, data_, ucell_,
+                               k_d_, ModuleBase::Vector3<double>(0.0, 0.0, 0.0), 4, q_cart_);
         pert_.init(ucell_, &pw_rho_, &pw_wfc_, sf_);
         q0_.init(ucell_, &pw_rho_, &pw_wfc_, &pert_);
     }
 
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
+
     // wfc-basis index of the reciprocal vector (ix, iy, iz)/a at Gamma
     int IgOf(int ix, int iy, int iz) const
     {
@@ -47,7 +67,9 @@ class DFPTQ0SerialTest : public DFPTSerialBase
         for (int ig = 0; ig < npwk; ++ig)
         {
             const ModuleBase::Vector3<double> g = pw_wfc_.getgpluskcar(0, ig);
-            if (std::llround(g.x * a_) == ix && std::llround(g.y * a_) == iy && std::llround(g.z * a_) == iz)
+            if (std::llround(g.x * dfpt_test::cubic_edge) == ix
+                && std::llround(g.y * dfpt_test::cubic_edge) == iy
+                && std::llround(g.z * dfpt_test::cubic_edge) == iz)
             {
                 return ig;
             }
@@ -56,8 +78,6 @@ class DFPTQ0SerialTest : public DFPTSerialBase
     }
 };
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
 #include <cmath>
 #include <complex>
 #include <vector>
@@ -120,7 +140,7 @@ TEST_F(DFPTQ0SerialTest, PosMatrixKineticAndDegenerateSkip)
 
 TEST_F(DFPTQ0SerialTest, PosMatrixNonlocalMatchesOperatorFiniteDifference)
 {
-    MakeNCAtom();
+    dfpt_test::make_nc_atom(ucell_);
     const int npwk = pw_wfc_.npwk[0];
     const int ig0 = IgOf(0, 0, 0);
     ASSERT_GE(ig0, 0);
diff --git a/source/source_pw/module_dfpt/test_serial/test_dfpt_rho.cpp b/source/source_pw/module_dfpt/test_serial/test_dfpt_rho.cpp
index 953f2f99246..df5407ed5ce 100644
--- a/source/source_pw/module_dfpt/test_serial/test_dfpt_rho.cpp
+++ b/source/source_pw/module_dfpt/test_serial/test_dfpt_rho.cpp
@@ -6,15 +6,19 @@
 
 #include "gtest/gtest.h"
 
-#include "dfpt_serial_fixture.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_base/constants.h"
 #include "source_base/matrix.h"
-#include "source_basis/module_pw/pw_basis_k.h"
 #include "source_psi/psi.h"
 #include "source_pw/module_dfpt/dfpt_kq_basis.h"
-#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_pw/module_dfpt/dfpt_rho.h"
 
+
 namespace
 {
 
@@ -35,18 +39,43 @@ std::complex<double> crand()
 
 } // namespace
 
-// per-file fixture (self-contained, gtest style)
-class DFPTRhoSerialTest : public DFPTSerialBase
+// per-file self-contained fixture (gtest style): owns its objects and
+// calls the dfpt_test free-function utilities
+class DFPTRhoSerialTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModulePW::PW_Basis pw_rho_;
+    ModulePW::PW_Basis_K pw_wfc_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+    ModuleBase::Vector3<double> q_cart_;
     ModuleDFPT::DFPT_Rho rho_;
 
     static const int nbands_ = 2;
 
+    // default (k, q) of this file: q is generic and k = -q so k+q = 0
+    const ModuleBase::Vector3<double> k_d_{-0.13, 0.0, -0.07};
+    const ModuleBase::Vector3<double> q_d_{0.13, 0.0, 0.07};
+
     void SetUp() override
     {
-        DFPTSerialBase::SetUp();
-        rho_.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, G_, std::string("rho_plain"), 0.4, 0.0});
+        dfpt_test::setup_cell(ucell_, latvec_);
+        SetupRho(k_d_, q_d_);
+    }
+
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
+
+    // (re)initialize the bases and the plain rho mixer for a given (k, q)
+    void SetupRho(const ModuleBase::Vector3<double>& k_d, const ModuleBase::Vector3<double>& q_d)
+    {
+        dfpt_test::setup_bases(pw_rho_, pw_wfc_, qlist_, data_, ucell_, k_d, q_d, nbands_, q_cart_);
+        rho_.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, ucell_.G, std::string("rho_plain"), 0.4, 0.0});
     }
 
     void FillRandomStates(psi::Psi<std::complex<double>>& psi,
@@ -114,7 +143,7 @@ TEST_F(DFPTRhoSerialTest, ComputeDrhoMatchesBruteForceGSpace)
         const int mx = (ix <= pw_rho_.nx / 2) ? ix : ix - pw_rho_.nx;
         const int my = (iy <= pw_rho_.ny / 2) ? iy : iy - pw_rho_.ny;
         const int mz = (iz <= pw_rho_.nz / 2) ? iz : iz - pw_rho_.nz;
-        const ModuleBase::Vector3<double> delta = ModuleBase::Vector3<double>(mx, my, mz) * G_;
+        const ModuleBase::Vector3<double> delta = ModuleBase::Vector3<double>(mx, my, mz) * ucell_.G;
         // A_Delta = (2 w / omega) * sum_G c*_G d_{G+Delta}: the spin factor
         // 2 sits in the band weight w1 = 2 w / omega (the QE incdrhoscf
         // convention, a915352cd), brute-forced over the lists
@@ -212,8 +241,8 @@ TEST_F(DFPTRhoSerialTest, ChargeConservationAtGamma)
     // rebuild the fixture bases with q = k = 0
     ModuleBase::Vector3<double> klist0[1] = {ModuleBase::Vector3<double>(0.0, 0.0, 0.0)};
     ModulePW::PW_Basis_K pw_wfc0;
-    pw_wfc0.initgrids(lat0_, latvec_, pw_rho_.nx, pw_rho_.ny, pw_rho_.nz);
-    pw_wfc0.initparameters(false, ecutwfc_, 1, klist0);
+    pw_wfc0.initgrids(dfpt_test::lat0, latvec_, pw_rho_.nx, pw_rho_.ny, pw_rho_.nz);
+    pw_wfc0.initparameters(false, dfpt_test::ecutwfc, 1, klist0);
     pw_wfc0.fft_bundle.initfftmode(0);
     pw_wfc0.setuptransform();
     pw_wfc0.collect_local_pw();
@@ -225,7 +254,7 @@ TEST_F(DFPTRhoSerialTest, ChargeConservationAtGamma)
     ModuleDFPT::DFPT_PW_Data data0;
     data0.init(&qlist0, 1, nbands_, pw_wfc0.npwk_max, pw_rho_.nrxx, 1, 1, nullptr);
     ModuleDFPT::DFPT_Rho rho0;
-    rho0.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc0, G_, std::string("rho_plain"), 0.4, 0.0});
+    rho0.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc0, ucell_.G, std::string("rho_plain"), 0.4, 0.0});
 
     psi::Psi<std::complex<double>> psi(1, nbands_, pw_wfc0.npwk_max, pw_wfc0.npwk[0], true);
     ModuleDFPT::DFPT_KQ_Basis kq0;
@@ -328,14 +357,14 @@ TEST_F(DFPTRhoSerialTest, VHartreeQClosedFormAndZeroMode)
 // ---------------------------------------------------------------------------
 TEST_F(DFPTRhoSerialTest, DrhocLocalizesAtTheAtomNotItsMirror)
 {
-    MakeNlccTwoAtomCell();
-    SetupBases(k_d_, q_d_, 2);
+    dfpt_test::make_nlcc_two_atom_cell(ucell_);
+    SetupRho(k_d_, q_d_);
     ModuleDFPT::DFPT_Rho::Config cfg;
     cfg.nspin = 1;
     cfg.nrxx = pw_rho_.nrxx;
     cfg.pw_rho = &pw_rho_;
     cfg.pw_wfc = &pw_wfc_;
-    cfg.recip_matrix = G_;
+    cfg.recip_matrix = ucell_.G;
     cfg.mix_type = "rho_plain";
     cfg.mix_beta = 0.4;
     cfg.kerker_a2 = 1.0;
@@ -350,7 +379,7 @@ TEST_F(DFPTRhoSerialTest, DrhocLocalizesAtTheAtomNotItsMirror)
     ASSERT_TRUE(ucell_.atoms[it].ncpp.nlcc);
     // tau is stored in lat0-cartesian units (fixture convention: cell edge
     // a_ in lat0 units); the true fractional position divides by a_
-    const double inv_a = 1.0 / a_;
+    const double inv_a = 1.0 / dfpt_test::cubic_edge;
     const ModuleBase::Vector3<double> tau_frac(ucell_.atoms[it].tau[ucell_.iat2ia[iat]].x * inv_a,
                                                ucell_.atoms[it].tau[ucell_.iat2ia[iat]].y * inv_a,
                                                ucell_.atoms[it].tau[ucell_.iat2ia[iat]].z * inv_a);
diff --git a/source/source_pw/module_dfpt/test_serial/test_dfpt_rho_mix.cpp b/source/source_pw/module_dfpt/test_serial/test_dfpt_rho_mix.cpp
index 05e40a52bcb..60dbb7a2f8f 100644
--- a/source/source_pw/module_dfpt/test_serial/test_dfpt_rho_mix.cpp
+++ b/source/source_pw/module_dfpt/test_serial/test_dfpt_rho_mix.cpp
@@ -6,15 +6,19 @@
 
 #include "gtest/gtest.h"
 
-#include "dfpt_serial_fixture.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_base/constants.h"
 #include "source_base/matrix.h"
-#include "source_basis/module_pw/pw_basis_k.h"
 #include "source_psi/psi.h"
 #include "source_pw/module_dfpt/dfpt_kq_basis.h"
-#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_pw/module_dfpt/dfpt_rho.h"
 
+
 namespace
 {
 
@@ -35,18 +39,43 @@ std::complex<double> crand()
 
 } // namespace
 
-// per-file fixture (self-contained, gtest style)
-class DFPTRhoSerialTest : public DFPTSerialBase
+// per-file self-contained fixture (gtest style): owns its objects and
+// calls the dfpt_test free-function utilities
+class DFPTRhoSerialTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModulePW::PW_Basis pw_rho_;
+    ModulePW::PW_Basis_K pw_wfc_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+    ModuleBase::Vector3<double> q_cart_;
     ModuleDFPT::DFPT_Rho rho_;
 
     static const int nbands_ = 2;
 
+    // default (k, q) of this file: q is generic and k = -q so k+q = 0
+    const ModuleBase::Vector3<double> k_d_{-0.13, 0.0, -0.07};
+    const ModuleBase::Vector3<double> q_d_{0.13, 0.0, 0.07};
+
     void SetUp() override
     {
-        DFPTSerialBase::SetUp();
-        rho_.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, G_, std::string("rho_plain"), 0.4, 0.0});
+        dfpt_test::setup_cell(ucell_, latvec_);
+        SetupRho(k_d_, q_d_);
+    }
+
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
+
+    // (re)initialize the bases and the plain rho mixer for a given (k, q)
+    void SetupRho(const ModuleBase::Vector3<double>& k_d, const ModuleBase::Vector3<double>& q_d)
+    {
+        dfpt_test::setup_bases(pw_rho_, pw_wfc_, qlist_, data_, ucell_, k_d, q_d, nbands_, q_cart_);
+        rho_.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, ucell_.G, std::string("rho_plain"), 0.4, 0.0});
     }
 
     void FillRandomStates(psi::Psi<std::complex<double>>& psi,
@@ -150,7 +179,7 @@ TEST_F(DFPTRhoSerialTest, MixDrhoKerkerFirstStepIsPreconditionedScaledOutput)
     }
     ASSERT_GT(w2_min, 0.0);
     const double a2 = 4.0 * w2_min;
-    rho_k.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, G_, std::string("rho_kerker"), 0.7, a2});
+    rho_k.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, ucell_.G, std::string("rho_kerker"), 0.7, a2});
 
     std::vector<std::complex<double>> out(pw_rho_.npw);
     int n_small = 0;
@@ -240,7 +269,7 @@ TEST_F(DFPTRhoSerialTest, MixDrhoKerkerStabilizesStiffModelProblem)
 
     // plain beta = 0.7 on the stiff model diverges
     ModuleDFPT::DFPT_Rho rho_p;
-    rho_p.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, G_, std::string("rho_plain"), 0.7, 0.0});
+    rho_p.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, ucell_.G, std::string("rho_plain"), 0.7, 0.0});
     data_.set_drho_g(0, 0, std::vector<std::complex<double>>(npw, std::complex<double>(0.0, 0.0)));
     for (int it = 0; it < 40; ++it)
     {
@@ -253,7 +282,7 @@ TEST_F(DFPTRhoSerialTest, MixDrhoKerkerStabilizesStiffModelProblem)
     // kerker beta = 0.7 with a^2 = 9 w2_min (f ~ 0.1 on the stiff shell)
     // converges to the target
     ModuleDFPT::DFPT_Rho rho_k;
-    rho_k.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, G_, std::string("rho_kerker"), 0.7, 9.0 * w2_min});
+    rho_k.init({1, pw_rho_.nrxx, &pw_rho_, &pw_wfc_, ucell_.G, std::string("rho_kerker"), 0.7, 9.0 * w2_min});
     data_.set_drho_g(0, 0, std::vector<std::complex<double>>(npw, std::complex<double>(0.0, 0.0)));
     for (int it = 0; it < 300; ++it)
     {
@@ -280,13 +309,13 @@ TEST_F(DFPTRhoSerialTest, BroydenConvergesDiagonalSystemFast)
     // the binding shell; 0.72 for d = 0.3), i.e. roughly 100 plain
     // iterations to 1e-10; Modified Broyden on the few distinct
     // eigenvalues should converge in a handful of iterations.
-    SetupBases(k_d_, q_d_, 2);
+    SetupRho(k_d_, q_d_);
     ModuleDFPT::DFPT_Rho::Config cfg;
     cfg.nspin = 1;
     cfg.nrxx = pw_rho_.nrxx;
     cfg.pw_rho = &pw_rho_;
     cfg.pw_wfc = &pw_wfc_;
-    cfg.recip_matrix = G_;
+    cfg.recip_matrix = ucell_.G;
     cfg.mix_type = "rho_broyden";
     cfg.mix_beta = 0.4;
     cfg.kerker_a2 = 1.0;
@@ -349,13 +378,13 @@ TEST_F(DFPTRhoSerialTest, BroydenResetMixingAllowsFreshQAndSameQCycle)
     // allocated Mixing_Data exits through the one-object-one-data guard
     // (broyden_mixing.cpp) and kills the process. The same-q cycle must
     // also restart from a zero input density.
-    SetupBases(k_d_, q_d_, 2);
+    SetupRho(k_d_, q_d_);
     ModuleDFPT::DFPT_Rho::Config cfg;
     cfg.nspin = 1;
     cfg.nrxx = pw_rho_.nrxx;
     cfg.pw_rho = &pw_rho_;
     cfg.pw_wfc = &pw_wfc_;
-    cfg.recip_matrix = G_;
+    cfg.recip_matrix = ucell_.G;
     cfg.mix_type = "rho_broyden";
     cfg.mix_beta = 0.4;
     cfg.kerker_a2 = 1.0;
diff --git a/source/source_pw/module_dfpt/test_serial/test_dfpt_write_dyn.cpp b/source/source_pw/module_dfpt/test_serial/test_dfpt_write_dyn.cpp
index b77e56b5ee7..bfe4f6173d6 100644
--- a/source/source_pw/module_dfpt/test_serial/test_dfpt_write_dyn.cpp
+++ b/source/source_pw/module_dfpt/test_serial/test_dfpt_write_dyn.cpp
@@ -1,6 +1,14 @@
-#include "dfpt_serial_fixture.h"
+#include "dfpt_test_tool.h"
+#include "source_basis/module_pw/pw_basis.h"
+#include "source_basis/module_pw/pw_basis_k.h"
+#include "source_cell/qlist.h"
+#include "source_cell/unitcell.h"
+#include "source_base/complexmatrix.h"
+#include "source_pw/module_dfpt/dfpt_pw_data.h"
 #include "source_pw/module_dfpt/dfpt_write_dyn.h"
 
+#include "gtest/gtest.h"
+
 #include "source_base/matrix.h"
 #include "source_base/matrix3.h"
 #include "source_base/vector3.h"
@@ -20,17 +28,32 @@
 /// Writer-focused fixture: only the two-atom cell geometry and the
 /// qlist/data binding are needed; the plane-wave bases of the base
 /// SetUp are not on the writer path.
-class DFPTWriteDynTest : public DFPTSerialBase
+// Writer-focused fixture: only the two-atom cell geometry and the
+// qlist/data binding are needed; the plane-wave bases are not on the
+// writer path. Self-contained gtest style, calling the dfpt_test
+// free-function utilities.
+class DFPTWriteDynTest : public ::testing::Test
 {
   protected:
+    ModuleBase::Matrix3 latvec_;
+    UnitCell ucell_;
+    ModuleCell::QList qlist_;
+    ModuleDFPT::DFPT_PW_Data data_;
+
     void SetUp() override
     {
-        SetUpCell();
-        MakeTwoAtomCell();
-        // bind data to qlist exactly like SetupBases does (nat = 2)
+        dfpt_test::setup_cell(ucell_, latvec_);
+        dfpt_test::make_two_atom_cell(ucell_);
+        // bind data to qlist exactly like setup_bases does (nat = 2)
         data_.init(&qlist_, 1, 1, 1, 1, 1, 2, nullptr);
     }
 
+    void TearDown() override
+    {
+        delete[] ucell_.atoms;
+        ucell_.atoms = nullptr;
+    }
+
     /// install an explicit q list (Gamma-first or not) into qlist_
     void set_qvecs(const std::vector<ModuleBase::Vector3<double>>& qvecs)
     {