Clarify expectedFailure in the unittest docs. (#10953)

diff --git a/Doc/library/unittest.rst b/Doc/library/unittest.rst
index 8afbee6..acf9b495 100644
--- a/Doc/library/unittest.rst
+++ b/Doc/library/unittest.rst
@@ -585,8 +585,8 @@
 
 .. decorator:: expectedFailure
 
-   Mark the test as an expected failure.  If the test fails when run, the test
-   is not counted as a failure.
+   Mark the test as an expected failure.  If the test fails it will be
+   considered a success.  If the test passes, it will be considered a failure.
 
 .. exception:: SkipTest(reason)