Add better tests for manifest json schema

tests/clientlib/validate_manifest_test.py

@@ -1,8 +1,11 @@
 
+import jsonschema
+import jsonschema.exceptions
 import pytest
 
 from pre_commit.clientlib.validate_manifest import additional_manifest_check
 from pre_commit.clientlib.validate_manifest import InvalidManifestError
+from pre_commit.clientlib.validate_manifest import MANIFEST_JSON_SCHEMA
 from pre_commit.clientlib.validate_manifest import run
 
 
@@ -29,4 +32,31 @@ def test_additional_manifest_check_raises_for_bad_language():
     [{'language': 'python>2.6'}],
 ))
 def test_additional_manifest_check_is_ok_with_missing_language(obj):
-    additional_manifest_check(obj)
+    additional_manifest_check(obj)
+
+
+def is_valid_according_to_schema(obj, schema):
+    try:
+        jsonschema.validate(obj, schema)
+        return True
+    except jsonschema.exceptions.ValidationError:
+        return False
+
+
+@pytest.mark.parametrize(('manifest_obj', 'expected'), (
+    ([], False),
+    ([{'id': 'a', 'name': 'b', 'entry': 'c'}], True),
+    (
+        [{
+             'id': 'a',
+             'name': 'b',
+             'entry': 'c',
+             'language': 'python',
+             'expected_return_value': 0,
+        }],
+        True,
+    ),
+))
+def test_is_valid_according_to_schema(manifest_obj, expected):
+    ret = is_valid_according_to_schema(manifest_obj, MANIFEST_JSON_SCHEMA)
+    assert ret is expected