Add AppendPrefix middleware for ArtifactBackend

python_tests/artifact/test_prefix.py

@@ -0,0 +1,31 @@
+import io
+import uuid
+
+from optuna_dashboard.artifact.prefix import AppendPrefix
+
+from .stubs import InMemoryBackend
+
+
+def test_read_and_write() -> None:
+    artifact_id = str(uuid.uuid4())
+    dummy_content = b"Hello World"
+
+    backend = AppendPrefix(backend=InMemoryBackend(), prefix="my-")
+    backend.write(artifact_id, io.BytesIO(dummy_content))
+    with backend.open(artifact_id) as f:
+        actual = f.read()
+    assert actual == dummy_content
+    backend.remove(artifact_id)
+
+
+def test_check_prefix() -> None:
+    artifact_id = str(uuid.uuid4())
+    dummy_content = b"Hello World"
+
+    in_memory = InMemoryBackend()
+    backend = AppendPrefix(backend=in_memory, prefix="my-")
+    backend.write(artifact_id, io.BytesIO(dummy_content))
+
+    assert len(in_memory._data) == 1
+    key = list(in_memory._data.keys())[0]
+    assert key.startswith("my-")