CA-388587: Add fixtures and tests for testing filter_xapi_clusterd_db…

…() (#76)

Signed-off-by: Bernhard Kaindl <[email protected]>
(cherry picked from commit 9683fca)

tests/unit/conftest.py

@@ -88,3 +88,89 @@ def bugtool(imported_bugtool):
     # Cleanup the bugtool data dict after each test as tests may modify it:
     imported_bugtool.data = {}
     sys.argv = ["xen-bugtool", "--unlimited"]
+
+
+@pytest.fixture(scope="function")
+def in_tmpdir(tmpdir):
+    """
+    Run each test function in it's own temporary directory
+
+    This fixture warps pytest's built-in tmpdir fixture with a chdir()
+    to the tmpdir and a check for leftover files after the test returns.
+
+    Usage in a test function:
+
+    @pytest.usefixtures("in_tmpdir")
+    def test_foo(other_fixtures):
+        # ... test code that runs with the tmpdir as its working directory ...
+
+    # If the test function wants to use the in_tmpdir variable:
+    def test_foo(in_tmpdir):
+        in_tmpdir.mkdir("subdir").join("filename").write("content_for_testing")
+        # code under test, that runs with the tmpdir as its working directory:
+        with open("subdir/filename") as f:
+            assert f.read() == "content_for_testing"
+
+    Documentation on the wrapped tmpdir fixture:
+    https://docs.pytest.org/en/6.2.x/tmpdir.html#the-tmpdir-fixture
+    """
+
+    # Get the current directory:
+    curdir = os.getcwd()
+
+    # Change to the temporary directory:
+    os.chdir(str(tmpdir))
+
+    # Run the test:
+    yield tmpdir  # provide the fixture value to the pytest test function
+
+    # Change back to the original directory:
+    os.chdir(curdir)
+
+    # upon return, the tmpdir fixture will cleanup the temporary directory
+
+
+@pytest.fixture(scope="function")
+def bugtool_log(in_tmpdir, bugtool):
+    """Like in_tmpdir and check that no logs are left in XEN_BUGTOOL_LOG"""
+
+    in_tmpdir.mkdir("tmp")  # Create a tmp directory for use by test cases
+
+    in_tmpdir.join(bugtool.XEN_BUGTOOL_LOG).write("")  # create the log file
+
+    # Run the test:
+    yield bugtool  # provide the bugtool to the test function
+
+    log = in_tmpdir.join(bugtool.XEN_BUGTOOL_LOG).read()  # read the log file
+    if log:  # pragma: no cover
+        print("Content of " + bugtool.XEN_BUGTOOL_LOG + ":" + log, file=sys.stderr)
+        pytest.fail("Code under test left logs in " + bugtool.XEN_BUGTOOL_LOG)
+
+    # Cleanup the temporary directory to prepare to check leftover files:
+    os.remove(bugtool.XEN_BUGTOOL_LOG)
+    shutil.rmtree("tmp")
+
+    # Check for files that the code under test might have left:
+    files = in_tmpdir.listdir()
+    if files:  # pragma: no cover
+        print("Files left in temporary working dir:", files, file=sys.stderr)
+        pytest.fail("Code under test left files in the its working directory")
+
+    # upon return, the in_tmpdir switches back to the original directory
+
+
+@pytest.fixture(scope="function")
+def isolated_bugtool(bugtool_log):
+    """
+    Like `bugtool_log` and make the temporary working directory read-only
+    to prevent creating files in it
+    """
+
+    # Make the current cwd (a temporary directory) read-only:
+    os.chmod(".", 0o555)
+
+    yield bugtool_log  # runs the test function in the read-only directory
+
+    os.chmod(".", 0o777)  # restore write permissions (for cleanup)
+
+    # upon return, bugtool_log continues with its cleanup