Allow customisation of testtools.run --list-tests behaviour.

NEWS

@@ -91,6 +91,10 @@ Improvements
   partitioning analysis of events or sending feedback encapsulated in
   StreamResult events back to their source. (Robert Collins)
 
+* ``testtools.run.TestProgram`` now supports the ``TestRunner`` taking over
+  responsibility for formatting the output of ``--list-tests``.
+  (Robert Collins)
+
 * The error message for setUp and tearDown upcall errors was broken on Python
   3.4. (Monty Taylor, Robert Collins, #1140688)
 

doc/for-framework-folk.rst

@@ -431,6 +431,13 @@ If you a writing custom wrapping suites, consider implementing filter_by_ids
 to support this (though most wrappers that subclass ``unittest.TestSuite`` will
 work just fine [see ``testtools.testsuite.filter_by_ids`` for details.]
 
+Extensions to TestRunner
+========================
+
+To facilitate custom listing of tests, ``testtools.run.TestProgram`` attempts
+to call ``list`` on the ``TestRunner``, falling back to a generic
+implementation if it is not present.
+
 .. _`testtools API docs`: http://mumak.net/testtools/apidocs/
 .. _unittest: http://docs.python.org/library/unittest.html
 .. _fixture: http://pypi.python.org/pypi/fixtures

testtools/run.py

@@ -8,10 +8,13 @@ For instance, to run the testtools test suite.
  $ python -m testtools.run testtools.tests.test_suite
 """
 
+from functools import partial
 import os
 import unittest
 import sys
 
+from extras import safe_hasattr
+
 from testtools import TextTestResult
 from testtools.compat import classtypes, istext, unicode_output_stream
 from testtools.testsuite import filter_by_ids, iterate_tests, sorted_tests
@@ -35,14 +38,22 @@ else:
 class TestToolsTestRunner(object):
     """ A thunk object to support unittest.TestProgram."""
 
-    def __init__(self, verbosity=None, failfast=None, buffer=None):
+    def __init__(self, verbosity=None, failfast=None, buffer=None,
+        stdout=None):
         """Create a TestToolsTestRunner.
 
         :param verbosity: Ignored.
         :param failfast: Stop running tests at the first failure.
         :param buffer: Ignored.
+        :param stdout: Stream to use for stdout.
         """
         self.failfast = failfast
+        self.stdout = stdout
+
+    def list(self, test):
+        """List the tests that would be run if test() was run."""
+        for test in iterate_tests(test):
+            self.stdout.write('%s\n' % test.id())
 
     def run(self, test):
         "Run the given test case or test suite."
@@ -177,8 +188,12 @@ class TestProgram(object):
         if not self.listtests:
             self.runTests()
         else:
-            for test in iterate_tests(self.test):
+            runner = self._get_runner()
-                stdout.write('%s\n' % test.id())
+            if safe_hasattr(runner, 'list'):
+                runner.list(self.test)
+            else:
+                for test in iterate_tests(self.test):
+                    stdout.write('%s\n' % test.id())
 
     def usageExit(self, msg=None):
         if msg:
@@ -321,26 +336,32 @@ class TestProgram(object):
         if (self.catchbreak
             and getattr(unittest, 'installHandler', None) is not None):
             unittest.installHandler()
-        if self.testRunner is None:
+        testRunner = self._get_runner()
-            self.testRunner = TestToolsTestRunner
-        if isinstance(self.testRunner, classtypes()):
-            try:
-                testRunner = self.testRunner(verbosity=self.verbosity,
-                                             failfast=self.failfast,
-                                             buffer=self.buffer)
-            except TypeError:
-                # didn't accept the verbosity, buffer or failfast arguments
-                testRunner = self.testRunner()
-        else:
-            # it is assumed to be a TestRunner instance
-            testRunner = self.testRunner
         self.result = testRunner.run(self.test)
         if self.exit:
             sys.exit(not self.result.wasSuccessful())
+
+    def _get_runner(self):
+        if self.testRunner is None:
+            self.testRunner = TestToolsTestRunner
+        try:
+            testRunner = self.testRunner(verbosity=self.verbosity,
+                                         failfast=self.failfast,
+                                         buffer=self.buffer)
+        except TypeError:
+            # didn't accept the verbosity, buffer or failfast arguments
+            try:
+                testRunner = self.testRunner()
+            except TypeError:
+                # it is assumed to be a TestRunner instance
+                testRunner = self.testRunner
+        return testRunner
+
+
 ################
 
 def main(argv, stdout):
-    program = TestProgram(argv=argv, testRunner=TestToolsTestRunner,
+    program = TestProgram(argv=argv, testRunner=partial(TestToolsTestRunner, stdout=stdout),
         stdout=stdout)
 
 if __name__ == '__main__':

testtools/tests/test_run.py

@@ -97,6 +97,20 @@ class TestRun(TestCase):
         if fixtures is None:
             self.skipTest("Need fixtures")
 
+    def test_run_custom_list(self):
+        self.useFixture(SampleTestFixture())
+        tests = []
+        class CaptureList(run.TestToolsTestRunner):
+            def list(self, test):
+                tests.append(set([case.id() for case
+                    in testtools.testsuite.iterate_tests(test)]))
+        out = StringIO()
+        program = run.TestProgram(
+            argv=['prog', '-l', 'testtools.runexample.test_suite'],
+            stdout=out, testRunner=CaptureList)
+        self.assertEqual([set(['testtools.runexample.TestFoo.test_bar',
+            'testtools.runexample.TestFoo.test_quux'])], tests)
+
     def test_run_list(self):
         self.useFixture(SampleTestFixture())
         out = StringIO()