diff --git a/tests/ansible/lib/action/assert_equal.py b/tests/ansible/lib/action/assert_equal.py
new file mode 100644
index 00000000..b36e6e55
--- /dev/null
+++ b/tests/ansible/lib/action/assert_equal.py
@@ -0,0 +1,61 @@
+#
+# Print data structure diff on assertion failure.
+#
+# assert_equal:  left=some.result right={1:2}
+#
+
+__metaclass__ = type
+
+import unittest2
+
+from ansible.errors import AnsibleError
+from ansible.plugins.action import ActionBase
+from ansible.module_utils.six import string_types
+
+
+class TestCase(unittest2.TestCase):
+    def runTest(self):
+        pass
+
+
+def text_diff(a, b):
+    tc = TestCase()
+    tc.maxDiff = None
+    try:
+        tc.assertEqual(a, b)
+        return None
+    except AssertionError as e:
+        return str(e)
+
+
+class ActionModule(ActionBase):
+    ''' Fail with custom message '''
+
+    TRANSFERS_FILES = False
+    _VALID_ARGS = frozenset(('left', 'right'))
+
+    def run(self, tmp=None, task_vars=None):
+        result = super(ActionModule, self).run(tmp, task_vars or {})
+
+        left = self._templar.template(
+            self._task.args['left'],
+            convert_bare=True,
+            bare_deprecated=False,
+        )
+        right = self._templar.template(self._task.args['right'],
+            convert_bare=True,
+            bare_deprecated=False,
+        )
+
+        diff = text_diff(left, right)
+        if diff is None:
+            return {
+                'changed': False
+            }
+
+        return {
+            'changed': False,
+            'failed': True,
+            'msg': diff,
+            '_ansible_verbose_always': True,
+        }