Add pcre type.

tests/languages/all_test.py

@@ -1,5 +1,6 @@
 from __future__ import unicode_literals
 
+import inspect
 import pytest
 
 from pre_commit.languages.all import all_languages
@@ -7,7 +8,27 @@ from pre_commit.languages.all import languages
 
 
 @pytest.mark.parametrize('language', all_languages)
-def test_all_languages_support_interface(language):
-    assert hasattr(languages[language], 'install_environment')
-    assert hasattr(languages[language], 'run_hook')
+def test_install_environment_argspec(language):
+    expected_argspec = inspect.ArgSpec(
+        args=['repo_cmd_runner', 'version'],
+        varargs=None,
+        keywords=None,
+        defaults=('default',),
+    )
+    argspec = inspect.getargspec(languages[language].install_environment)
+    assert argspec == expected_argspec
+
+
+@pytest.mark.parametrize('language', all_languages)
+def test_ENVIRONMENT_DIR(language):
     assert hasattr(languages[language], 'ENVIRONMENT_DIR')
+
+
+@pytest.mark.parametrize('language', all_languages)
+def test_run_hook_argpsec(language):
+    expected_argspec = inspect.ArgSpec(
+        args=['repo_cmd_runner', 'hook', 'file_args'],
+        varargs=None, keywords=None, defaults=None,
+    )
+    argspec = inspect.getargspec(languages[language].run_hook)
+    assert argspec == expected_argspec

tests/languages/helpers_test.py

@@ -0,0 +1,16 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+from pre_commit.languages.helpers import file_args_to_stdin
+
+
+def test_file_args_to_stdin_empty():
+    assert file_args_to_stdin([]) == ''
+
+
+def test_file_args_to_stdin_some():
+    assert file_args_to_stdin(['foo', 'bar']) == 'foo\nbar\n'
+
+
+def test_file_args_to_stdin_tuple():
+    assert file_args_to_stdin(('foo', 'bar')) == 'foo\nbar\n'