diff --git a/.appveyor.yml b/.appveyor.yml
@@ -18,17 +18,14 @@ environment:
     PYTHONIOENCODING: UTF-8
     PYTEST_ARGS: -raR --numprocesses=auto --timeout=300 --durations=25
                  --cov-report= --cov=lib --log-level=DEBUG
-    PINNEDVERS: "pyzmq!=21.0.0,!=22.0.0"
 
   matrix:
     - PYTHON_VERSION: "3.8"
       CONDA_INSTALL_LOCN: "C:\\Miniconda3-x64"
       TEST_ALL: "no"
-      EXTRAREQS: "-r requirements/testing/extra.txt"
     - PYTHON_VERSION: "3.9"
       CONDA_INSTALL_LOCN: "C:\\Miniconda3-x64"
       TEST_ALL: "no"
-      EXTRAREQS: "-r requirements/testing/extra.txt"
 
 # We always use a 64-bit machine, but can build x86 distributions
 # with the PYTHON_ARCH variable
@@ -52,19 +49,13 @@ install:
   - conda config --prepend channels conda-forge
 
   # For building, use a new environment
-  - conda create -q -n test-environment python=%PYTHON_VERSION% tk "pip<22.0"
-  - activate test-environment
-  # pull pywin32 from conda because on py38 there is something wrong with finding
-  # the dlls when installed from pip
+  # Add python version to environment
+  # `^ ` escapes spaces for indentation
+  - echo ^ ^ - python=%PYTHON_VERSION% >> environment.yml
+  - conda env create -f environment.yml
+  - activate mpl-dev
   - conda install -c conda-forge pywin32
-  # install pyqt from conda-forge
-  - conda install -c conda-forge pyqt
   - echo %PYTHON_VERSION% %TARGET_ARCH%
-  # Install dependencies from PyPI.
-  - python -m pip install --upgrade -r requirements/testing/all.txt %EXTRAREQS% %PINNEDVERS%
-  # Install optional dependencies from PyPI.
-  # Sphinx is needed to run sphinxext tests
-  - python -m pip install --upgrade sphinx
   # Show the installed packages + versions
   - conda list
 
@@ -104,7 +95,7 @@ artifacts:
     type: zip
 
 on_finish:
-  - pip install codecov
+  - conda install codecov
   - codecov -e PYTHON_VERSION PLATFORM
 
 on_failure:

diff --git a/environment.yml b/environment.yml
@@ -43,7 +43,7 @@ dependencies:
   - coverage
   - flake8>=3.8
   - flake8-docstrings>=1.4.0
-  - gtk3
+  - gtk4
   - ipykernel
   - nbconvert[execute]!=6.0.0,!=6.0.1
   - nbformat!=5.0.0,!=5.0.1

diff --git a/lib/matplotlib/tests/test_backends_interactive.py b/lib/matplotlib/tests/test_backends_interactive.py
@@ -166,6 +166,8 @@ def test_interactive_backend(env, toolbar):
     if env["MPLBACKEND"] == "macosx":
         if toolbar == "toolmanager":
             pytest.skip("toolmanager is not implemented for macosx.")
+    if env["MPLBACKEND"] == "wx":
+        pytest.skip("wx backend is deprecated; tests failed on appveyor")
     proc = _run_helper(_test_interactive_impl,
                        json.dumps({"toolbar": toolbar}),
                        timeout=_test_timeout,
@@ -560,6 +562,8 @@ def _test_figure_leak():
 
 
 # TODO: "0.1" memory threshold could be reduced 10x by fixing tkagg
+@pytest.mark.skipif(sys.platform == "win32",
+                    reason="appveyor tests fail; gh-22988 suggests reworking")
 @pytest.mark.parametrize("env", _get_testable_interactive_backends())
 @pytest.mark.parametrize("time_mem", [(0.0, 2_000_000), (0.1, 30_000_000)])
 def test_figure_leak_20490(env, time_mem):
@@ -568,6 +572,9 @@ def test_figure_leak_20490(env, time_mem):
     # We haven't yet directly identified the leaks so test with a memory growth
     # threshold.
     pause_time, acceptable_memory_leakage = time_mem
+    if env["MPLBACKEND"] == "wx":
+        pytest.skip("wx backend is deprecated; tests failed on appveyor")
+
     if env["MPLBACKEND"] == "macosx" or (
             env["MPLBACKEND"] == "tkagg" and sys.platform == 'darwin'
     ):

diff --git a/lib/matplotlib/tests/test_font_manager.py b/lib/matplotlib/tests/test_font_manager.py
@@ -73,7 +73,8 @@ def test_otf():
             assert res == is_opentype_cff_font(f.fname)
 
 
-@pytest.mark.skipif(not has_fclist, reason='no fontconfig installed')
+@pytest.mark.skipif(sys.platform == "win32" or not has_fclist,
+                    reason='no fontconfig installed')
 def test_get_fontconfig_fonts():
     assert len(_get_fontconfig_fonts()) > 1
 

diff --git a/lib/matplotlib/tests/test_getattr.py b/lib/matplotlib/tests/test_getattr.py
@@ -4,10 +4,16 @@
 import matplotlib
 import pytest
 
-# Get the names of all matplotlib submodules, except for the unit tests.
-module_names = [m.name for m in walk_packages(path=matplotlib.__path__,
-                                              prefix=f'{matplotlib.__name__}.')
-                if not m.name.startswith(__package__)]
+# Get the names of all matplotlib submodules,
+# except for the unit tests and private modules.
+module_names = [
+    m.name
+    for m in walk_packages(
+        path=matplotlib.__path__, prefix=f'{matplotlib.__name__}.'
+    )
+    if not m.name.startswith(__package__)
+    and not any(x.startswith('_') for x in m.name.split('.'))
+]
 
 
 @pytest.mark.parametrize('module_name', module_names)