Fix tests (#15)

* Use fixture for the test class.

* use scope as function for the fixture.

* Run tests in temporary directory.

papergit/tests/bin/test_commands.py

@@ -7,6 +7,7 @@
 from papergit.bin.paper_git import main
 
 
+@pytest.mark.usefixtures('initialize_fixture')
 class TestPaperGitCommand(object):
     """Tests for the main paper-git command."""
 
@@ -36,5 +37,5 @@ def test_initialization(self):
         with patch('sys.argv', testargs), \
                 patch('sys.stdout', output), patch('sys.stderr', error):
             main()
-        assert '' in output.getvalue()
-        assert '' in error.getvalue()
+        assert output.getvalue() == ''
+        assert error.getvalue() == ''

papergit/tests/conftest.py

@@ -16,7 +16,7 @@
 """)
 
 
-@pytest.fixture(scope="session")
+@pytest.fixture
 def initialize_fixture(tmpdir_factory, request):
     print("\nInitializing tests ...\n")
     testing_dir = tmpdir_factory.mktemp('var')
@@ -29,3 +29,6 @@ def teardown():
         print("\nTearing down ...\n")
 
     request.addfinalizer(teardown)
+
+    with testing_dir.as_cwd():
+        yield