remove redundant importing overhead for newly built test module in test runner...

remove redundant importing overhead for newly built test module in test runner and make sure we always import exactly the one we just built

runtests.py

@@ -293,6 +293,20 @@ def parse_tags(filepath):
 list_unchanging_dir = memoize(lambda x: os.listdir(x))
 
 
+def import_ext(module_name, file_path=None):
+    if file_path:
+        import imp
+        return imp.load_dynamic(module_name, file_path)
+    else:
+        try:
+            from importlib import invalidate_caches
+        except ImportError:
+            pass
+        else:
+            invalidate_caches()
+        return __import__(module_name, globals(), locals(), ['*'])
+
+
 class build_ext(_build_ext):
     def build_extension(self, ext):
         try:
@@ -554,7 +568,8 @@ class CythonCompileTestCase(unittest.TestCase):
         self.success = True
 
     def runCompileTest(self):
-        self.compile(self.test_directory, self.module, self.workdir,
+        return self.compile(
+            self.test_directory, self.module, self.workdir,
             self.test_directory, self.expect_errors, self.annotate)
 
     def find_module_source_file(self, source_file):
@@ -698,6 +713,8 @@ class CythonCompileTestCase(unittest.TestCase):
         finally:
             os.chdir(cwd)
 
+        return build_extension.get_ext_fullpath(module)
+
     def compile(self, test_directory, module, workdir, incdir,
                 expect_errors, annotate):
         expected_errors = errors = ()
@@ -732,9 +749,13 @@ class CythonCompileTestCase(unittest.TestCase):
                 print('\n'.join(errors))
                 print('\n')
                 raise
+            return None
+
+        if self.cython_only:
+            so_path = None
         else:
-            if not self.cython_only:
-                self.run_distutils(test_directory, module, workdir, incdir)
+            so_path = self.run_distutils(test_directory, module, workdir, incdir)
+        return so_path
 
 class CythonRunTestCase(CythonCompileTestCase):
     def shortDescription(self):
@@ -751,10 +772,10 @@ class CythonRunTestCase(CythonCompileTestCase):
             self.setUp()
             try:
                 self.success = False
-                self.runCompileTest()
+                ext_so_path = self.runCompileTest()
                 failures, errors = len(result.failures), len(result.errors)
                 if not self.cython_only:
-                    self.run_tests(result)
+                    self.run_tests(result, ext_so_path)
                 if failures == len(result.failures) and errors == len(result.errors):
                     # No new errors...
                     self.success = True
@@ -768,12 +789,13 @@ class CythonRunTestCase(CythonCompileTestCase):
         except Exception:
             pass
 
-    def run_tests(self, result):
-        self.run_doctests(self.module, result)
+    def run_tests(self, result, ext_so_path):
+        self.run_doctests(result, ext_so_path)
 
-    def run_doctests(self, module_name, result):
+    def run_doctests(self, result, ext_so_path):
         def run_test(result):
-            tests = doctest.DocTestSuite(module_name)
+            module = import_ext(self.module, ext_so_path)
+            tests = doctest.DocTestSuite(module)
             tests.run(result)
         run_forked_test(result, run_test, self.shortDescription(), self.fork)
 
@@ -932,8 +954,9 @@ class CythonUnitTestCase(CythonRunTestCase):
     def shortDescription(self):
         return "compiling (%s) tests in %s" % (self.language, self.module)
 
-    def run_tests(self, result):
-        unittest.defaultTestLoader.loadTestsFromName(self.module).run(result)
+    def run_tests(self, result, ext_so_path):
+        module = import_ext(self.module, ext_so_path)
+        unittest.defaultTestLoader.loadTestsFromModule(module).run(result)
 
 
 class CythonPyregrTestCase(CythonRunTestCase):
@@ -965,7 +988,7 @@ class CythonPyregrTestCase(CythonRunTestCase):
     def _run_doctest(self, result, module):
         self.run_doctests(module, result)
 
-    def run_tests(self, result):
+    def run_tests(self, result, ext_so_path):
         try:
             from test import support
         except ImportError: # Python2.x
@@ -984,7 +1007,7 @@ class CythonPyregrTestCase(CythonRunTestCase):
             try:
                 try:
                     sys.stdout.flush() # helps in case of crashes
-                    module = __import__(self.module)
+                    module = import_ext(self.module, ext_so_path)
                     sys.stdout.flush() # helps in case of crashes
                     if hasattr(module, 'test_main'):
                         module.test_main()