Fail command lines that use multiprocessing and other options together. #495

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/test_cmdline.py b/tests/test_cmdline.py
index d72fd83c..f2531605 100644
--- a/tests/test_cmdline.py
+++ b/tests/test_cmdline.py
@@ -464,6 +464,16 @@ class CmdLineTest(BaseCmdLineTest):
         out = self.stdout()
         self.assertIn("option --concurrency: invalid choice: 'multiprocessing,gevent'", out)
 
+    def test_multiprocessing_needs_config_file(self):
+        # You can't use command-line args to add options to multiprocessing
+        # runs, since they won't make it to the subprocesses. You need to use a
+        # config file.
+        self.command_line("run --concurrency=multiprocessing --branch foo.py", ret=ERR)
+        self.assertIn(
+            "Options affecting multiprocessing must be specified in a configuration file.",
+            self.stdout()
+        )
+
     def test_run_debug(self):
         self.cmd_executes("run --debug=opt1 foo.py", """\
             .coverage(debug=["opt1"])