Add check-docstring-first hook.

tests/check_docstring_first_test.py

@@ -0,0 +1,67 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import io
+
+import pytest
+
+from pre_commit_hooks.check_docstring_first import check_docstring_first
+from pre_commit_hooks.check_docstring_first import main
+
+
+# Contents, expected, expected_output
+TESTS = (
+    # trivial
+    ('', 0, ''),
+    # Acceptable
+    ('"foo"', 0, ''),
+    # Docstrin after code
+    (
+        'from __future__ import unicode_literals\n'
+        '"foo"\n',
+        1,
+        '{filename}:2 Module docstring appears after code '
+        '(code seen on line 1).\n'
+    ),
+    # Test double docstring
+    (
+        '"The real docstring"\n'
+        'from __future__ import absolute_import\n'
+        '"fake docstring"\n',
+        1,
+        '{filename}:3 Multiple module docstrings '
+        '(first docstring on line 1).\n'
+    ),
+    # Test multiple lines of code above
+    (
+        'import os\n'
+        'import sys\n'
+        '"docstring"\n',
+        1,
+        '{filename}:3 Module docstring appears after code '
+        '(code seen on line 1).\n',
+    ),
+    # String literals in expressions are ok.
+    ('x = "foo"\n', 0, ''),
+)
+
+
+all_tests = pytest.mark.parametrize(
+    ('contents', 'expected', 'expected_out'), TESTS,
+)
+
+
+@all_tests
+def test_unit(capsys, contents, expected, expected_out):
+    assert check_docstring_first(contents) == expected
+    assert capsys.readouterr()[0] == expected_out.format(filename='<unknown>')
+
+
+@all_tests
+def test_integration(tmpdir, capsys, contents, expected, expected_out):
+    tmpfilename = tmpdir.join('test.py').strpath
+    with io.open(tmpfilename, 'w') as tmpfile:
+        tmpfile.write(contents)
+
+    assert main([tmpfilename]) == expected
+    assert capsys.readouterr()[0] == expected_out.format(filename=tmpfilename)