diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 0c5b7a08ced5..fd6eac7ce279 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -240,9 +240,13 @@ jobs:
 
           cat mplsetup.cfg
 
-          # All dependencies must have been pre-installed, so that the minver
-          # constraints are held.
-          python -m pip install --no-deps -ve .
+          if [[ "${{ matrix.name-suffix }}" == '(Minimum Versions)' ]]; then
+            # Minimum versions run does not use build isolation so that it
+            # builds against the pre-installed minver dependencies.
+            python -m pip install --no-deps --no-build-isolation -ve .
+          else
+            python -m pip install --no-deps -ve .
+          fi
 
           if [[ "${{ runner.os }}" != 'macOS' ]]; then
             unset CPPFLAGS
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 000000000000..ef70e1893299
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,7 @@
+[build-system]
+build-backend = "setuptools.build_meta"
+requires = [
+    "certifi>=2020.06.20",
+    "numpy>=1.19",
+    "setuptools_scm>=7",
+]
diff --git a/setup.py b/setup.py
index d1f1de7078ff..a460718684a8 100644
--- a/setup.py
+++ b/setup.py
@@ -34,6 +34,9 @@
 import setuptools.command.build_py
 import setuptools.command.sdist
 
+# sys.path modified to find setupext.py during pyproject.toml builds.
+sys.path.append(str(Path(__file__).resolve().parent))
+
 import setupext
 from setupext import print_raw, print_status
 
@@ -68,6 +71,12 @@ def has_flag(self, flagname):
 
 class BuildExtraLibraries(setuptools.command.build_ext.build_ext):
     def finalize_options(self):
+        # If coverage is enabled then need to keep the .o and .gcno files in a
+        # non-temporary directory otherwise coverage info not collected.
+        cppflags = os.getenv('CPPFLAGS')
+        if cppflags and '--coverage' in cppflags:
+            self.build_temp = 'build'
+
         self.distribution.ext_modules[:] = [
             ext
             for package in good_packages
@@ -208,8 +217,9 @@ def update_matplotlibrc(path):
 class BuildPy(setuptools.command.build_py.build_py):
     def run(self):
         super().run()
-        update_matplotlibrc(
-            Path(self.build_lib, "matplotlib/mpl-data/matplotlibrc"))
+        if not self.editable_mode:
+            update_matplotlibrc(
+                Path(self.build_lib, "matplotlib/mpl-data/matplotlibrc"))
 
 
 class Sdist(setuptools.command.sdist.sdist):
@@ -300,11 +310,6 @@ def make_release_tree(self, base_dir, files):
     package_data=package_data,
 
     python_requires='>={}'.format('.'.join(str(n) for n in py_min_version)),
-    setup_requires=[
-        "certifi>=2020.06.20",
-        "numpy>=1.19",
-        "setuptools_scm>=7",
-    ],
     install_requires=[
         "contourpy>=1.0.1",
         "cycler>=0.10",