diff --git a/python_tests/artifact/test_backend.py b/python_tests/artifact/test_backend.py
index 14a470e3..52fe6027 100644
--- a/python_tests/artifact/test_backend.py
+++ b/python_tests/artifact/test_backend.py
@@ -1,3 +1,5 @@
+import base64
+import json
 import tempfile
 from unittest.mock import MagicMock
 
@@ -177,3 +179,73 @@ def test_successful_trial_artifact_retrieval() -> None:
         )
         assert status == 200
         assert body == b"dummy_content"
+
+
+DUMMY_DATA_URL = (
+    f"data:text/plain; charset=utf-8,{base64.b64encode(b'dummy_content').decode('utf-8')}"
+)
+
+
+def test_upload_artifact_invalid_no_trial() -> None:
+    storage = optuna.storages.InMemoryStorage()
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        artifact_store = FileSystemArtifactStore(tmpdir)
+
+        app = create_app(storage, artifact_store)
+        study = optuna.create_study(storage=storage)
+
+        status, _, body = send_request(
+            app,
+            f"/api/artifacts/{study._study_id}/0",
+            "POST",
+            body=json.dumps({"file": DUMMY_DATA_URL}),
+            content_type="application/json",
+        )
+        assert status == 500  # TODO(contramundum53): This should return 400
+
+
+def test_upload_artifact_invalid_complete_trial() -> None:
+    storage = optuna.storages.InMemoryStorage()
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        artifact_store = FileSystemArtifactStore(tmpdir)
+
+        app = create_app(storage, artifact_store)
+        study = optuna.create_study(storage=storage)
+
+        study.add_trial(optuna.create_trial(value=1.0, distributions={}, params={}))
+        trial = study.trials[-1]
+        status, _, body = send_request(
+            app,
+            f"/api/artifacts/{study._study_id}/{trial._trial_id}",
+            "POST",
+            body=json.dumps({"file": DUMMY_DATA_URL}),
+            content_type="application/json",
+        )
+        assert status == 400
+
+
+def test_upload_artifact() -> None:
+    storage = optuna.storages.InMemoryStorage()
+
+    study = optuna.create_study(storage=storage)
+    with tempfile.TemporaryDirectory() as tmpdir:
+        artifact_store = FileSystemArtifactStore(tmpdir)
+
+        app = create_app(storage, artifact_store)
+
+        study.add_trial(optuna.create_trial(state=optuna.trial.TrialState.RUNNING))
+        trial = study.trials[-1]
+        status, _, body = send_request(
+            app,
+            f"/api/artifacts/{study._study_id}/{trial._trial_id}",
+            "POST",
+            body=json.dumps({"file": DUMMY_DATA_URL}),
+            content_type="application/json",
+        )
+        assert status == 201
+        res = json.loads(body)
+        with open(f"{tmpdir}/{res['artifact_id']}", "r") as f:
+            data = f.read()
+            assert data == "dummy_content"