Simplify the tests
diff --git a/tests/requirements_txt_fixer_test.py b/tests/requirements_txt_fixer_test.py
index 3680733..fe51f4a 100644
--- a/tests/requirements_txt_fixer_test.py
+++ b/tests/requirements_txt_fixer_test.py
@@ -1,5 +1,3 @@
-import os.path
-
 import pytest
 
 from pre_commit_hooks.requirements_txt_fixer import fix_requirements_txt
@@ -22,13 +20,11 @@
 
 @pytest.mark.parametrize(('input_s', 'expected_retval', 'output'), TESTS)
 def test_integration(input_s, expected_retval, output, tmpdir):
-    path = os.path.join(tmpdir.strpath, 'file.txt')
+    path = tmpdir.join('file.txt')
+    path.write_binary(input_s)
 
-    with open(path, 'wb') as file_obj:
-        file_obj.write(input_s)
-
-    assert fix_requirements_txt([path]) == expected_retval
-    assert open(path, 'rb').read() == output
+    assert fix_requirements_txt([path.strpath]) == expected_retval
+    assert path.read_binary() == output
 
 
 def test_requirement_object():