Assert validity of stream parameters.

recipe_engine/unittests/stream_test.py

Index: recipe_engine/unittests/stream_test.py
diff --git a/recipe_engine/unittests/stream_test.py b/recipe_engine/unittests/stream_test.py
index 365bc1c99fa4520c8a3c47150cecd23dc4af06d7..748d29d7a94e1f109b3a56b5989e6db065588c22 100755
--- a/recipe_engine/unittests/stream_test.py
+++ b/recipe_engine/unittests/stream_test.py
@@ -161,5 +161,48 @@ bar tries to kiss foo, but foo already left
       with self.assertRaises(AssertionError):
         foo.set_step_status('SUCCESS')
 
+  def test_content_assertions(self):
+    with stream.StreamEngineInvariants() as engine:
+      with self.assertRaises(ValueError):
+        engine.make_step_stream('foo\nbar')
+
+      # Test StepStream.
+      s = engine.make_step_stream('foo')
+      with self.assertRaises(ValueError):
+        s.new_log_stream('foo\nbar')
+      ls = s.new_log_stream('foo')
+
+      with self.assertRaises(ValueError):
+        s.add_step_text('foo\nbar')
+      s.add_step_text('foo')
+
+      with self.assertRaises(ValueError):
+        s.add_step_summary_text('foo\nbar')
+      s.add_step_summary_text('foo')
+
+      with self.assertRaises(ValueError):
+        s.add_step_link('foo\nbar', 'baz')
+      with self.assertRaises(ValueError):
+        s.add_step_link('foo', 'bar\nbaz')
+      s.add_step_link('foo', 'bar')
+
+      with self.assertRaises(ValueError):
+        s.set_build_property('foo\nbar', 'true')
+      with self.assertRaises(ValueError):
+        s.set_build_property('foo', 'true\n')
+      with self.assertRaises(ValueError):
+        s.set_build_property('foo', 'NOT JSON')
+      s.set_build_property('foo', '"Is JSON"')
+
+      with self.assertRaises(ValueError):
+        s.trigger('true\n')
+      with self.assertRaises(ValueError):
+        s.trigger('NOT JSON')
+      s.trigger('"Is JSON"')
+
+      ls.close()
+      s.close()
+
+
 if __name__ == '__main__':
   unittest.main()