--- a/tests/run-tests.py	Sun May 28 15:47:00 2017 -0400
+++ b/tests/run-tests.py	Tue May 30 20:47:00 2017 -0400
@@ -1767,6 +1767,8 @@
                 if not v:
                     channel = n
                     break
+            else:
+                raise ValueError('Could not find output channel')
             channels[channel] = "=" + test.name[5:].split(".")[0]
             try:
                 test(result)