diff --git a/src/_pytest/pytester.py b/src/_pytest/pytester.py
index 1cf6515a0..532d799f2 100644
--- a/src/_pytest/pytester.py
+++ b/src/_pytest/pytester.py
@@ -312,7 +312,8 @@ class HookRecorder(object):
                     passed.append(rep)
             elif rep.skipped:
                 skipped.append(rep)
-            elif rep.failed:
+            else:
+                assert rep.failed, "Unexpected outcome: {!r}".format(rep)
                 failed.append(rep)
         return passed, skipped, failed