Merge pull request #4980 from blueyed/fixup_namespace_packages

monkeypatch.syspath_prepend: call fixup_namespace_packages

src/_pytest/monkeypatch.py

@@ -262,10 +262,15 @@ class MonkeyPatch(object):
 
     def syspath_prepend(self, path):
         """ Prepend ``path`` to ``sys.path`` list of import locations. """
+        from pkg_resources import fixup_namespace_packages
+
         if self._savesyspath is None:
             self._savesyspath = sys.path[:]
         sys.path.insert(0, str(path))
 
+        # https://github.com/pypa/setuptools/blob/d8b901bc/docs/pkg_resources.txt#L162-L171
+        fixup_namespace_packages(str(path))
+
     def chdir(self, path):
         """ Change the current working directory to the specified path.
         Path can be a string or a py.path.local object.

src/_pytest/pytester.py

@@ -593,11 +593,16 @@ class Testdir(object):
 
         This is undone automatically when this object dies at the end of each
         test.
-
         """
+        from pkg_resources import fixup_namespace_packages
+
         if path is None:
             path = self.tmpdir
-        sys.path.insert(0, str(path))
+
+        dirname = str(path)
+        sys.path.insert(0, dirname)
+        fixup_namespace_packages(dirname)
+
         # a call to syspathinsert() usually means that the caller wants to
         # import some dynamically created files, thus with python3 we
         # invalidate its import caches
@@ -606,12 +611,10 @@ class Testdir(object):
     def _possibly_invalidate_import_caches(self):
         # invalidate caches if we can (py33 and above)
         try:
-            import importlib
+            from importlib import invalidate_caches
         except ImportError:
-            pass
-        else:
-            if hasattr(importlib, "invalidate_caches"):
-                importlib.invalidate_caches()
+            return
+        invalidate_caches()
 
     def mkdir(self, name):
         """Create a new (sub)directory."""