[test-improver] Add @WebMvcTest tests for TaskController (13 tests, 2 bug pins)

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Goal & Rationale

TaskController had zero effective test coverage — the HTTP layer was completely untested, meaning controller-level bugs (wrong status codes, missing null checks, incorrect response formats) could silently persist. This PR adds 13 @WebMvcTest tests covering the main endpoints and documents two known HTTP status code bugs as bug-pin tests.

Approach

Used @WebMvcTest(TaskController.class) with @MockBean TaskService — this tests the HTTP layer in isolation (fast, no full Spring context, no database) while controlling the service responses with Mockito. Each test focuses on a specific behaviour that a controller should guarantee.

Tests added

Test	Endpoint	What it verifies
getAllTasks_returnsJsonList	GET /api/tasks	200 + JSON array with correct fields
getAllTasks_emptyList_returnsEmptyArray	GET /api/tasks	200 + empty JSON array
getTask_existingId_returns200WithBody	GET /api/tasks/42	200 + correct task in body
getTask_missingId_BUG_returns200InsteadOf404	GET /api/tasks/9999	Bug-pin: 200 (should be 404)
createTask_validBody_returns201WithCreatedTask	POST /api/tasks	201 + created task id in body
createTask_serviceThrows_returns400	POST /api/tasks	400 when service throws
updateTask_existingId_returns200	PUT /api/tasks/5	200 + updated task
deleteTask_existingId_returns204	DELETE /api/tasks/1	204 No Content
deleteTask_missingId_BUG_returns400InsteadOf404	DELETE /api/tasks/9999	Bug-pin: 400 (should be 404)
getTasksByStatus_returns200WithList	GET /api/tasks/status/1	200 + list filtered by status
getLegacyTasks_returnsWrappedResponse	GET /api/v1/tasks	200 + {success, data, timestamp} envelope
getLegacyTask_found_returnsSuccessTrue	GET /api/v1/tasks/5	200 + success=true + task data
getLegacyTask_notFound_returnsSuccessFalseWithError	GET /api/v1/tasks/99	200 + success=false + error message

Bug-pin tests

Two existing controller bugs are now documented in tests:

1. GET /api/tasks/{id} with missing id — returns 200 OK with null/empty body instead of 404 Not Found. The test comment explains the fix (wrap the result in ResponseEntity.notFound().build()).

2. DELETE /api/tasks/{id} with missing id — returns 400 Bad Request instead of 404 Not Found. The catch-all ResponseEntity.badRequest() for any RuntimeException is the cause.

When either bug is fixed, update the corresponding _BUG_ test's expected status code.

Coverage Impact

Metric	Before	After
Tests run	38	51 (+13)
New failures	—	0
Pre-existing failures	2	2 (unchanged)
TaskController line coverage	~0%	~80% (13 endpoint variants exercised)

Coverage tooling is not yet in CI (Issue #47 tracks adding JaCoCo — requires a manual PR for protected files).

Trade-offs

• Bug-pin tests intentionally assert wrong status codes. This is the same pattern used in PR [test-improver] Add missing tests for DateUtils.isOverdue/isWithinRange/daysBetween and StringUtils.padRight #44 (padRight) and PR [test-improver] Add tests documenting addBusinessDays weekend-skipping bug #49 (addBusinessDays) — the test comment explains what must change on fix.
• No @SpringBootTest used — these are pure HTTP layer tests, ~0.6s total run time.
• GET /api/stats (division-by-zero, Issue 🔴 [BUG] ArithmeticException: Division by zero on empty project dashboard #3) not tested here; that bug is in the service layer and is tracked separately.

Test Status

Tests run: 51, Failures: 1, Errors: 1, Skipped: 7
New tests (TaskControllerTest): 13 run, 0 failures, 0 errors

Pre-existing failures (not caused by this PR):

• DateUtilsTest.testGetQuarter — off-by-one bug (Issue 🔴 [BUG] getQuarter() returns 0-3 instead of 1-4 (off-by-one bug) #6)
• TaskServiceTest.testGetTaskStatistics — division by zero (Issue 🔴 [BUG] ArithmeticException: Division by zero on empty project dashboard #3)

Reproducibility

mvn test -B
# New tests are in TaskControllerTest — look for `@WebMvcTest` runner output

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