Give error if --run arg does not match a scenario

2 files changed, 10 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index a1d18cc..ab72d5d 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,12 @@ NEWS for cmdtest
 
 This file summarizes changes between releases of cmdtest.
 
+Version 0.19, released UNRELEASED
+---------------------------------
+
+* Yarn now gives an error if `--run` is given a scenario that doens't
+  exist.
+
 Version 0.18, released 2015-11-06
 ---------------------------------
 
diff --git a/yarn b/yarn
index bcd22d3..3ca0bd5 100755
--- a/yarn
+++ b/yarn
@@ -292,6 +292,10 @@ class YarnRunner(cliapp.Application):
                     if matches(s.name, name) and s not in result:
                         result.append(s)
                         break
+                else:
+                    raise cliapp.AppException(
+                        'Requested scenario %s does not exist' %
+                        name)
             return result
 
         return scenarios