stages: add small unit test for the gzip stage

stages/test/test_gzip.py

@@ -0,0 +1,41 @@
+#!/usr/bin/python3
+
+from unittest.mock import patch
+
+import pytest
+
+STAGE_NAME = "org.osbuild.gzip"
+
+
+@pytest.mark.parametrize("test_options,expected_level", [
+    # our default
+    ({}, "-1"),
+    # custom settings
+    ({"level": "1"}, "-1"),
+    ({"level": "6"}, "-6"),
+    ({"level": "9"}, "-9"),
+])
+@patch("subprocess.run")
+def test_gzip_compression_default_to_level1(mocked_run, tmp_path, stage_module, test_options, expected_level):
+    inp = {
+        "file": {
+            "path": "/input/file/path",
+            "data": {
+                "files": {
+                    "hash:value": "some-file",
+                }
+            },
+        },
+    }
+    output = tmp_path
+    options = {
+        "filename": "out.tar.gz",
+    }
+    options.update(test_options)
+
+    stage_module.main(inp, output, options)
+    assert len(mocked_run.call_args_list) == 1
+    args, kwargs = mocked_run.call_args_list[0]
+    assert args == (["gzip", "--no-name", "--stdout", expected_level, "/input/file/path/hash:value"],)
+    assert kwargs["check"]
+    assert kwargs["stdout"].name.endswith("out.tar.gz")