From a3bfd4de13e415c3c8267762311340579967cbbb Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Mon, 19 Aug 2013 18:53:54 +0100
Subject: Complain if a scenario has no THENs

---
 NEWS                      |  3 +++
 yarn                      | 15 +++++++++++++++
 yarn.tests/no-then.exit   |  1 +
 yarn.tests/no-then.script | 14 ++++++++++++++
 yarn.tests/no-then.stderr |  3 +++
 5 files changed, 36 insertions(+)
 create mode 100644 yarn.tests/no-then.exit
 create mode 100755 yarn.tests/no-then.script
 create mode 100644 yarn.tests/no-then.stderr

diff --git a/NEWS b/NEWS
index 35bbc38..92c1e37 100644
--- a/NEWS
+++ b/NEWS
@@ -14,6 +14,9 @@ Version 0.10, released UNRELEASED
 * A new option, `--timings`, has been added to yarn to report how long
   each scenario and each step took.
 
+* Yarn now complains if a scenario has no THEN steps. Suggested by
+  Richard Maw.
+
 Version 0.9, released 2013-07-23
 --------------------------------
 
diff --git a/yarn b/yarn
index ce0b9cb..3bb26e8 100755
--- a/yarn
+++ b/yarn
@@ -108,6 +108,7 @@ class YarnRunner(cliapp.Application):
                 'step %Index(step,steps): %String(step_name)')
 
         scenarios, implementations = self.parse_scenarios(args)
+        self.check_for_thens(scenarios)
         self.connect_implementations(scenarios, implementations)
         shell_prelude = self.load_shell_libraries()
 
@@ -157,6 +158,20 @@ class YarnRunner(cliapp.Application):
 
         return block_parser.scenarios, block_parser.implementations
 
+    def check_for_thens(self, scenarios):
+        no_thens = []
+        for scenario in scenarios:
+            for step in scenario.steps:
+                if step.what == 'THEN':
+                    break
+            else:
+                no_thens.append(scenario)
+
+        if no_thens:
+            raise cliapp.AppException(
+                'Some scenarios have no THENs:\n%s' %
+                ''.join('  "%s"\n' % s.name for s in scenarios))
+
     def connect_implementations(self, scenarios, implementations):
         for scenario in scenarios:
             for step in scenario.steps:
diff --git a/yarn.tests/no-then.exit b/yarn.tests/no-then.exit
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/yarn.tests/no-then.exit
@@ -0,0 +1 @@
+1
diff --git a/yarn.tests/no-then.script b/yarn.tests/no-then.script
new file mode 100755
index 0000000..491853f
--- /dev/null
+++ b/yarn.tests/no-then.script
@@ -0,0 +1,14 @@
+#!/bin/sh
+
+set -eu
+
+
+cat <<EOF > "$DATADIR/1.yarn"
+    SCENARIO    foo
+    WHEN        doing ok
+
+    IMPLEMENTS WHEN doing ok
+    true
+EOF
+
+./run-yarn "$DATADIR/1.yarn"
diff --git a/yarn.tests/no-then.stderr b/yarn.tests/no-then.stderr
new file mode 100644
index 0000000..b018036
--- /dev/null
+++ b/yarn.tests/no-then.stderr
@@ -0,0 +1,3 @@
+ERROR: Some scenarios have no THENs:
+  "foo"
+
-- 
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