Fix a bug with test classes that use setup_method

Author: astrofrog

CHANGES.md

@@ -1,7 +1,8 @@
 0.8 (unreleased)
 ----------------
 
-- No changes yet.
+- Fixed use of mpl_image_compare on methods of test classes that also
+  use setup_method. [#50]
 
 0.7 (2016-11-26)
 ----------------

pytest_mpl/plugin.py

@@ -164,7 +164,12 @@ def item_function_wrapper(*args, **kwargs):
                 # Run test and get figure object
                 import inspect
                 if inspect.ismethod(original):  # method
-                    fig = original(*args[1:], **kwargs)
+                    # In some cases, for example if setup_method is used,
+                    # original appears to belong to an instance of the test
+                    # class that is not the same as args[0], and args[0] is the
+                    # one that has the correct attributes set up from setup_method
+                    # so we ignore original.__self__ and use args[0] instead.
+                    fig = original.__func__(*args, **kwargs)
                 else:  # function
                     fig = original(*args, **kwargs)
 

tests/test_pytest_mpl.py

@@ -189,3 +189,19 @@ def test_parametrized(s):
     ax = fig.add_subplot(1, 1, 1)
     ax.scatter([1,3,4,3,2],[1,4,3,3,1], s=s)
     return fig
+
+
+class TestClassWithSetup(object):
+
+    # Regression test for a bug that occurred when using setup_method
+
+    def setup_method(self, method):
+        self.x = [1, 2, 3]
+
+    @pytest.mark.mpl_image_compare(baseline_dir=baseline_dir_local,
+                                   filename='test_succeeds.png')
+    def test_succeeds(self):
+        fig = plt.figure()
+        ax = fig.add_subplot(1, 1, 1)
+        ax.plot(self.x)
+        return fig