mock-call-count-retry-fallback

Mock Call Count Failures After Adding Retry/Fallback Logic

Problem

When you add retry logic, fallback mechanisms, or alternative code paths to a service, existing tests that verify exact mock method call counts will fail. The tests were written for the original behavior and don't account for the new retry/fallback calls.

Context / Trigger Conditions

• Test fails with: Expected: <N>, Actual: <M> where M > N
• Error message: "Unexpected number of calls"
• MissingStubError: 'methodName' No stub was found which matches the arguments
• You recently added:
  • Retry logic (e.g., retry after timeout)
  • Fallback mechanisms (e.g., try primary server, fall back to secondary)
  • Alternative code paths (e.g., try REST API, fall back to WebSocket)
• The failing test uses verify(...).called(N) assertions

Solution

Step 1: Identify the New Code Paths

Trace through your new retry/fallback logic to understand:

• How many times the mocked method will now be called
• What new methods are being called that weren't before

Step 2: Mock New Dependencies

If your fallback code calls methods that weren't previously mocked:

// BEFORE: Only mocked the primary method
when(mockService.primaryMethod(any)).thenAnswer((_) async => 'result');

// AFTER: Also mock fallback-related methods
when(mockService.primaryMethod(any)).thenAnswer((_) async => 'result');
when(mockService.addFallbackServer(any)).thenAnswer((_) async => false);  // Graceful failure
when(mockService.queryFallback(any)).thenAnswer((_) async => []);

Step 3: Update Expected Call Counts

// BEFORE: Expected single call
verify(mockService.createSubscription(...)).called(1);

// AFTER: Expected calls = initial + retries
// Document WHY the count changed
verify(mockService.createSubscription(...)).called(2);  // initial + retry after fallback

Step 4: Add Comments Explaining the Count

// Verify subscription was created
// Note: With the indexer fallback logic, createSubscription is called twice:
// 1. First attempt via main relay batch fetch
// 2. Retry attempt after indexer fallback fails
verify(
  mockService.createSubscription(...),
).called(2);