Refactor test cases for improved readability and consistency

- Updated test functions in various test files to enhance code clarity by formatting long lines and improving indentation.
- Adjusted assertions to use multi-line formatting for better readability.
- Added new test cases for theme settings API to ensure proper functionality.
- Ensured consistent use of line breaks and spacing across test files for uniformity.

tests/unit/test_simulation.py

@@ -19,7 +19,12 @@ def client(api_client: TestClient) -> TestClient:
 
 def test_run_simulation_function_generates_samples():
     params: List[Dict[str, Any]] = [
-        {"name": "grade", "value": 1.8, "distribution": "normal", "std_dev": 0.2},
+        {
+            "name": "grade",
+            "value": 1.8,
+            "distribution": "normal",
+            "std_dev": 0.2,
+        },
         {
             "name": "recovery",
             "value": 0.9,
@@ -45,7 +50,10 @@ def test_run_simulation_with_zero_iterations_returns_empty():
 @pytest.mark.parametrize(
     "parameter_payload,error_message",
     [
-        ({"name": "missing-value"}, "Parameter at index 0 must include 'value'"),
+        (
+            {"name": "missing-value"},
+            "Parameter at index 0 must include 'value'",
+        ),
         (
             {
                 "name": "bad-dist",
@@ -110,7 +118,8 @@ def test_run_simulation_triangular_sampling_path():
     span = 10.0 * DEFAULT_UNIFORM_SPAN_RATIO
     rng = Random(seed)
     expected_samples = [
-        rng.triangular(10.0 - span, 10.0 + span, 10.0) for _ in range(iterations)
+        rng.triangular(10.0 - span, 10.0 + span, 10.0)
+        for _ in range(iterations)
     ]
     actual_samples = [entry["result"] for entry in results]
     for actual, expected in zip(actual_samples, expected_samples):
@@ -156,9 +165,7 @@ def test_simulation_endpoint_no_params(client: TestClient):
     assert resp.json()["detail"] == "No parameters provided"
 
 
-def test_simulation_endpoint_success(
-    client: TestClient, db_session: Session
-):
+def test_simulation_endpoint_success(client: TestClient, db_session: Session):
     scenario_payload: Dict[str, Any] = {
         "name": f"SimScenario-{uuid4()}",
         "description": "Simulation test",
@@ -168,7 +175,12 @@ def test_simulation_endpoint_success(
     scenario_id = scenario_resp.json()["id"]
 
     params: List[Dict[str, Any]] = [
-        {"name": "param1", "value": 2.5, "distribution": "normal", "std_dev": 0.5}
+        {
+            "name": "param1",
+            "value": 2.5,
+            "distribution": "normal",
+            "std_dev": 0.5,
+        }
     ]
     payload: Dict[str, Any] = {
         "scenario_id": scenario_id,