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_reporting.py

@@ -50,9 +50,11 @@ def test_generate_report_with_values():
 
 
 def test_generate_report_single_value():
-    report = generate_report([
-        {"iteration": 1, "result": 42.0},
-    ])
+    report = generate_report(
+        [
+            {"iteration": 1, "result": 42.0},
+        ]
+    )
     assert report["count"] == 1
     assert report["std_dev"] == 0.0
     assert report["variance"] == 0.0
@@ -105,8 +107,10 @@ def test_reporting_endpoint_success(client: TestClient):
 validation_error_cases: List[tuple[List[Any], str]] = [
     (["not-a-dict"], "Entry at index 0 must be an object"),
     ([{"iteration": 1}], "Entry at index 0 must include numeric 'result'"),
-    ([{"iteration": 1, "result": "bad"}],
-     "Entry at index 0 must include numeric 'result'"),
+    (
+        [{"iteration": 1, "result": "bad"}],
+        "Entry at index 0 must include numeric 'result'",
+    ),
 ]