Add tests for dockerfile paths to ensure backwards compatibility

Author: enpaul

tests/test_parser.py

@@ -1517,3 +1517,13 @@ def test_alt_dockerfile_names(self, tmpdir):
 
         validate = DockerfileParser(path=tmpdir, dockerfile_filename="Containerfile")
         assert validate.baseimage == out.baseimage
+
+    def test_dockerfile_path_compatibility(self, tmpdir):
+        parser = DockerfileParser(path=tmpdir)
+        assert str(parser.dockerfile) == parser.dockerfile_path
+        assert parser.dockerfile == tmpdir / "Dockerfile"
+
+        with (tmpdir / "nothing").open("w+") as testfile:
+            nullparser = DockerfileParser(fileobj=testfile)
+            assert nullparser.dockerfile is None
+            assert nullparser.dockerfile_path is None