diff --git a/test/test_metadata_writer.py b/test/test_metadata_writer.py
index 062f25b..4376840 100644
--- a/test/test_metadata_writer.py
+++ b/test/test_metadata_writer.py
@@ -1,7 +1,31 @@
-from photools3.metadata_writer import read_metadata
+from pathlib import Path
+
+import pytest
+
+from photools3.metadata_writer import MetadataWriter
 from test.test_photo import PATHS_DNG_EXAMPLES
 
 
-def test_read_metadata():
-    result = read_metadata(PATHS_DNG_EXAMPLES[0])
+@pytest.fixture
+def make_dng_file(tmp_path):
+    def _make(index: int = 0) -> Path:
+        src = PATHS_DNG_EXAMPLES[index]
+        dst = tmp_path / f"copy_{index}_{src.name}"
+        return dst
+    return _make
+
+@pytest.fixture
+def dng_file(make_dng):
+    return make_dng()
+
+def test_read_metadata(make_dng_file):
+    """primitive test for `MetadataWriter`"""
+    file_path = make_dng_file()
+    result = MetadataWriter(file_path)
     assert result
+
+@pytest.mark.parametrize("idx", range(len(PATHS_DNG_EXAMPLES)))
+def test_read_metadata_sidecar_path(make_dng_file, idx):
+    file_path = make_dng_file(idx)
+    metadata_writer = MetadataWriter(file_path)
+    assert isinstance(metadata_writer.sidecar_path, Path)