Added tests for check_toml

Also assures we print filename when error occurs.

pre_commit_hooks/check_toml.py

@@ -19,7 +19,7 @@ def main(argv=None):  # type: (Optional[Sequence[str]]) -> int
             with open(filename) as f:
                 toml.load(f)
         except toml.TomlDecodeError as exc:
-            print(exc)
+            print('{}: {}'.format(filename, exc))
             retval = 1
     return retval
 

tests/check_toml_test.py

@@ -0,0 +1,32 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+from pre_commit_hooks.check_toml import main
+
+
+def test_toml_good(tmpdir):
+    filename = tmpdir.join('f')
+    filename.write("""
+key = # INVALID
+
+= "no key name"  # INVALID
+""")
+    ret = main((filename.strpath,))
+    assert ret == 1
+
+
+def test_toml_bad(tmpdir):
+    filename = tmpdir.join('f')
+    filename.write(
+        """
+# This is a TOML document.
+
+title = "TOML Example"
+
+[owner]
+name = "John"
+dob = 1979-05-27T07:32:00-08:00 # First class dates
+""",
+    )
+    ret = main((filename.strpath,))
+    assert ret == 0