tests: check `test` command run tests only once

setuptools/tests/test_test.py

@@ -4,6 +4,7 @@ from __future__ import unicode_literals
 
 from distutils import log
 import os
+import sys
 
 import pytest
 
@@ -66,13 +67,13 @@ def sample_test(tmpdir_cwd):
 
 
 @pytest.fixture
-def silent_log():
+def quiet_log():
     # Running some of the other tests will automatically
     # change the log level to info, messing our output.
     log.set_verbosity(0)
 
 
-@pytest.mark.usefixtures('sample_test', 'silent_log')
+@pytest.mark.usefixtures('sample_test', 'quiet_log')
 def test_test(capfd):
     params = dict(
         name='foo',
@@ -90,3 +91,41 @@ def test_test(capfd):
         cmd.run()
     out, err = capfd.readouterr()
     assert out == 'Foo\n'
+
+
+@pytest.mark.xfail(
+    sys.version_info < (2, 7),
+    reason="No discover support for unittest on Python 2.6",
+)
+@pytest.mark.usefixtures('tmpdir_cwd', 'quiet_log')
+def test_tests_are_run_once(capfd):
+    params = dict(
+        name='foo',
+        packages=['dummy'],
+    )
+    with open('setup.py', 'wt') as f:
+        f.write('from setuptools import setup; setup(\n')
+        for k, v in sorted(params.items()):
+            f.write('    %s=%r,\n' % (k, v))
+        f.write(')\n')
+    os.makedirs('dummy')
+    with open('dummy/__init__.py', 'wt'):
+        pass
+    with open('dummy/test_dummy.py', 'wt') as f:
+        f.write(DALS(
+            """
+            from __future__ import print_function
+            import unittest
+            class TestTest(unittest.TestCase):
+                def test_test(self):
+                    print('Foo')
+             """))
+    dist = Distribution(params)
+    dist.script_name = 'setup.py'
+    cmd = test(dist)
+    cmd.ensure_finalized()
+    # The test runner calls sys.exit
+    with contexts.suppress_exceptions(SystemExit):
+        cmd.run()
+    out, err = capfd.readouterr()
+    assert out == 'Foo\n'