#17282: Document unittest.main defaultTest argument.
diff --git a/Doc/library/unittest.rst b/Doc/library/unittest.rst
index 5157b26..fcfd514 100644
--- a/Doc/library/unittest.rst
+++ b/Doc/library/unittest.rst
@@ -1801,6 +1801,10 @@
if __name__ == '__main__':
unittest.main(verbosity=2)
+ The *defaultTest* argument is the name of the test to run if no test names
+ are specified via *argv*. If not specified or ``None`` and no test names are
+ provided via *argv*, all tests found in *module* are run.
+
The *argv* argument can be a list of options passed to the program, with the
first element being the program name. If not specified or ``None``,
the values of :data:`sys.argv` are used.