tests: introduce fixture to change back to right dir

Tests changing the working directory could leave us stranded somewhere
where all following tests could fail. Make sure to always go back on
failure.

Signed-off-by: Henning Schild <henning.schild@siemens.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

tests/test_refspec.py

@@ -25,10 +25,16 @@ import shutil
 from kas import kas
 from kas.libkas import run_cmd
 
-import pytest  # noqa: F401; flake8 'pytest' imported but unused
+import pytest
 
 
-def test_refspec_switch(tmpdir):
+@pytest.fixture
+def changedir():
+    yield
+    os.chdir(os.path.join(os.path.dirname(__file__), '..'))
+
+
+def test_refspec_switch(changedir, tmpdir):
     """
         Test that the local git clone is correctly updated when switching
         between a commit hash refspec and a branch refspec.
@@ -36,7 +42,6 @@ def test_refspec_switch(tmpdir):
     tdir = str(tmpdir.mkdir('test_refspec_switch'))
     shutil.rmtree(tdir, ignore_errors=True)
     shutil.copytree('tests/test_refspec', tdir)
-    prev_dir = os.path.realpath(os.getcwd())
     os.chdir(tdir)
 
     kas.kas(['shell', 'test.yml', '-c', 'true'])
@@ -66,5 +71,3 @@ def test_refspec_switch(tmpdir):
                            fail=False, liveupdate=False)
     assert rc == 0
     assert output.strip() == '907816a5c4094b59a36aec12226e71c461c05b77'
-
-    os.chdir(prev_dir)