diff --git a/tests/sort_simple_yaml_test.py b/tests/sort_simple_yaml_test.py
new file mode 100644
index 0000000..176d12f
--- /dev/null
+++ b/tests/sort_simple_yaml_test.py
@@ -0,0 +1,120 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import os
+
+import pytest
+
+from pre_commit_hooks.sort_simple_yaml import first_key
+from pre_commit_hooks.sort_simple_yaml import main
+from pre_commit_hooks.sort_simple_yaml import parse_block
+from pre_commit_hooks.sort_simple_yaml import parse_blocks
+from pre_commit_hooks.sort_simple_yaml import sort
+
+RETVAL_GOOD = 0
+RETVAL_BAD = 1
+TEST_SORTS = [
+    (
+        ['c: true', '', 'b: 42', 'a: 19'],
+        ['b: 42', 'a: 19', '', 'c: true'],
+        RETVAL_BAD,
+    ),
+
+    (
+        ['# i am', '# a header', '', 'c: true', '', 'b: 42', 'a: 19'],
+        ['# i am', '# a header', '', 'b: 42', 'a: 19', '', 'c: true'],
+        RETVAL_BAD,
+    ),
+
+    (
+        ['# i am', '# a header', '', 'already: sorted', '', 'yup: i am'],
+        ['# i am', '# a header', '', 'already: sorted', '', 'yup: i am'],
+        RETVAL_GOOD,
+    ),
+
+    (
+        ['# i am', '# a header'],
+        ['# i am', '# a header'],
+        RETVAL_GOOD,
+    ),
+]
+
+
+@pytest.mark.parametrize('bad_lines,good_lines,retval', TEST_SORTS)
+def test_integration_good_bad_lines(tmpdir, bad_lines, good_lines, retval):
+    file_path = os.path.join(tmpdir.strpath, 'foo.yaml')
+
+    with open(file_path, 'w') as f:
+        f.write("\n".join(bad_lines) + "\n")
+
+    assert main([file_path]) == retval
+
+    with open(file_path, 'r') as f:
+        assert [line.rstrip() for line in f.readlines()] == good_lines
+
+
+def test_parse_header():
+    lines = ['# some header', '# is here', '', 'this is not a header']
+    assert parse_block(lines, header=True) == ['# some header', '# is here']
+    assert lines == ['', 'this is not a header']
+
+    lines = ['this is not a header']
+    assert parse_block(lines, header=True) == []
+    assert lines == ['this is not a header']
+
+
+def test_parse_block():
+    # a normal block
+    lines = ['a: 42', 'b: 17', '', 'c: 19']
+    assert parse_block(lines) == ['a: 42', 'b: 17']
+    assert lines == ['', 'c: 19']
+
+    # a block at the end
+    lines = ['c: 19']
+    assert parse_block(lines) == ['c: 19']
+    assert lines == []
+
+    # no block
+    lines = []
+    assert parse_block(lines) == []
+    assert lines == []
+
+
+def test_parse_blocks():
+    # normal blocks
+    lines = ['a: 42', 'b: 17', '', 'c: 19']
+    assert parse_blocks(lines) == [['a: 42', 'b: 17'], ['c: 19']]
+    assert lines == []
+
+    # a single block
+    lines = ['a: 42', 'b: 17']
+    assert parse_blocks(lines) == [['a: 42', 'b: 17']]
+    assert lines == []
+
+    # no blocks
+    lines = []
+    assert parse_blocks(lines) == []
+    assert lines == []
+
+
+def test_first_key():
+    # first line
+    lines = ['a: 42', 'b: 17', '', 'c: 19']
+    assert first_key(lines) == 'a: 42'
+
+    # second line
+    lines = ['# some comment', 'a: 42', 'b: 17', '', 'c: 19']
+    assert first_key(lines) == 'a: 42'
+
+    # second line with quotes
+    lines = ['# some comment', '"a": 42', 'b: 17', '', 'c: 19']
+    assert first_key(lines) == 'a": 42'
+
+    # no lines
+    lines = []
+    assert first_key(lines) is None
+
+
+@pytest.mark.parametrize('bad_lines,good_lines,_', TEST_SORTS)
+def test_sort(bad_lines, good_lines, _):
+    assert sort(bad_lines) == good_lines