Backport PR #15199: MNT/TST: generalize check_figures_equal to work with pytest.marks

anntzer · meeseeksmachine · commit b3ae232c8430 · 2020-03-16T22:12:02.000Z
diff --git a/lib/matplotlib/testing/decorators.py b/lib/matplotlib/testing/decorators.py
@@ -381,41 +381,40 @@ def test_plot(fig_test, fig_ref):
             fig_test.subplots().plot([1, 3, 5])
             fig_ref.subplots().plot([0, 1, 2], [1, 3, 5])
     """
-
+    POSITIONAL_OR_KEYWORD = inspect.Parameter.POSITIONAL_OR_KEYWORD
     def decorator(func):
         import pytest
 
         _, result_dir = _image_directories(func)
 
-        if len(inspect.signature(func).parameters) == 2:
-            # Free-standing function.
-            @pytest.mark.parametrize("ext", extensions)
-            def wrapper(ext):
-                fig_test = plt.figure("test")
-                fig_ref = plt.figure("reference")
-                func(fig_test, fig_ref)
-                test_image_path = result_dir / (func.__name__ + "." + ext)
-                ref_image_path = (
-                    result_dir / (func.__name__ + "-expected." + ext))
-                fig_test.savefig(test_image_path)
-                fig_ref.savefig(ref_image_path)
-                _raise_on_image_difference(
-                    ref_image_path, test_image_path, tol=tol)
-
-        elif len(inspect.signature(func).parameters) == 3:
-            # Method.
-            @pytest.mark.parametrize("ext", extensions)
-            def wrapper(self, ext):
-                fig_test = plt.figure("test")
-                fig_ref = plt.figure("reference")
-                func(self, fig_test, fig_ref)
-                test_image_path = result_dir / (func.__name__ + "." + ext)
-                ref_image_path = (
-                    result_dir / (func.__name__ + "-expected." + ext))
-                fig_test.savefig(test_image_path)
-                fig_ref.savefig(ref_image_path)
-                _raise_on_image_difference(
-                    ref_image_path, test_image_path, tol=tol)
+        @pytest.mark.parametrize("ext", extensions)
+        def wrapper(*args, ext, **kwargs):
+            fig_test = plt.figure("test")
+            fig_ref = plt.figure("reference")
+            func(*args, fig_test=fig_test, fig_ref=fig_ref, **kwargs)
+            test_image_path = result_dir / (func.__name__ + "." + ext)
+            ref_image_path = result_dir / (
+                func.__name__ + "-expected." + ext
+            )
+            fig_test.savefig(test_image_path)
+            fig_ref.savefig(ref_image_path)
+            _raise_on_image_difference(
+                ref_image_path, test_image_path, tol=tol
+            )
+
+        sig = inspect.signature(func)
+        new_sig = sig.replace(
+            parameters=([param
+                         for param in sig.parameters.values()
+                         if param.name not in {"fig_test", "fig_ref"}]
+                        + [inspect.Parameter("ext", POSITIONAL_OR_KEYWORD)])
+        )
+        wrapper.__signature__ = new_sig
+
+        # reach a bit into pytest internals to hoist the marks from
+        # our wrapped function
+        new_marks = getattr(func, "pytestmark", []) + wrapper.pytestmark
+        wrapper.pytestmark = new_marks
 
         return wrapper
 
diff --git a/lib/matplotlib/tests/test_testing.py b/lib/matplotlib/tests/test_testing.py
@@ -1,7 +1,17 @@
 import warnings
 import pytest
+from matplotlib.testing.decorators import check_figures_equal
 
-@pytest.mark.xfail(strict=True,
-                   reason="testing that warnings fail tests")
+
+@pytest.mark.xfail(
+    strict=True, reason="testing that warnings fail tests"
+)
 def test_warn_to_fail():
     warnings.warn("This should fail the test")
+
+
+@pytest.mark.parametrize("a", [1])
+@check_figures_equal(extensions=["png"])
+@pytest.mark.parametrize("b", [1])
+def test_parametrize_with_check_figure_equal(a, fig_ref, b, fig_test):
+    assert a == b
