Add 'force_failure' feature to testtools.TestCase.

Change-Id: Idb8c8d0c837ab2cb6ec53c84d144c29b5d6da8ea

NEWS

@@ -23,6 +23,9 @@ Improvements
   exiting (2) when an import has failed rather than only signalling through the
   test name. (Robert Collins, #1245672)
 
+* Added ability for ``testtools.TestCase`` instances to force a test to
+  fail, even if no assertions failed. (Thomi Richards)
+
 * Added ``testtools.content.StacktraceContent``, a content object that
   automatically creates a ``StackLinesContent`` object containing the current
   stack trace. (Thomi Richards)

doc/for-framework-folk.rst

@@ -82,6 +82,15 @@ Test renaming
 instance to one with a new name.  This is helpful for implementing test
 parameterization.
 
+.. _force_failure:
+
+Delayed Test Failure
+--------------------
+
+Setting the ``testtools.TestCase.force_failure`` instance variable to True will
+cause ``testtools.RunTest`` to fail the test case after the test has finished.
+This is useful when you want to cause a test to fail, but don't want to
+prevent the remainder of the test code from being executed.
 
 Test placeholders
 =================

doc/for-test-authors.rst

@@ -1243,6 +1243,13 @@ Here are some tips for converting your Trial tests into testtools tests.
   ``AsynchronousDeferredRunTest`` does not.  If you rely on this behavior, use
   ``AsynchronousDeferredRunTestForBrokenTwisted``.
 
+force_failure
+-------------
+
+Setting the ``testtools.TestCase.force_failure`` instance variable to ``True``
+will cause the test to be marked as a failure, but won't stop the test code
+from running (see :ref:`force_failure`).
+
 
 Test helpers
 ============

testtools/runtest.py

@@ -135,6 +135,9 @@ class RunTest(object):
                         self._run_cleanups, self.result):
                         failed = True
                 finally:
+                    if getattr(self.case, 'force_failure', None):
+                        self._run_user(_raise_force_fail_error)
+                        failed = True
                     if not failed:
                         self.result.addSuccess(self.case,
                             details=self.case.getDetails())
@@ -200,6 +203,10 @@ class RunTest(object):
         raise e
 
 
+def _raise_force_fail_error():
+    raise AssertionError("Forced Test Failure")
+
+
 # Signal that this is part of the testing framework, and that code from this
 # should not normally appear in tracebacks.
 __unittest = True

testtools/testcase.py

@@ -155,6 +155,8 @@ class TestCase(unittest.TestCase):
     :ivar exception_handlers: Exceptions to catch from setUp, runTest and
         tearDown. This list is able to be modified at any time and consists of
         (exception_class, handler(case, result, exception_value)) pairs.
+    :ivar force_failure: Force testtools.RunTest to fail the test after the
+        test has completed.
     :cvar run_tests_with: A factory to make the ``RunTest`` to run tests with.
         Defaults to ``RunTest``.  The factory is expected to take a test case
         and an optional list of exception handlers.
@@ -924,7 +926,7 @@ class DecorateTestCaseResult(object):
 
     def __getattr__(self, name):
         return getattr(self.decorated, name)
-    
+
     def __delattr__(self, name):
         delattr(self.decorated, name)
 

testtools/tests/test_testcase.py

@@ -569,6 +569,16 @@ class TestAssertions(TestCase):
         self.assertFails(
             expected, self.assertThat, matchee, matcher, verbose=True)
 
+    def test__force_failure_fails_test(self):
+        class Test(TestCase):
+            def test_foo(self):
+                self.force_failure = True
+                self.remaining_code_run = True
+        test = Test('test_foo')
+        result = test.run()
+        self.assertFalse(result.wasSuccessful())
+        self.assertTrue(test.remaining_code_run)
+
     def get_error_string(self, e):
         """Get the string showing how 'e' would be formatted in test output.