Jasmine Async Test Hangs: A Diagnostic Guide for done() Callback and Promise Issues

The Problem: Tests That Never Complete

When a Jasmine test containing asynchronous operations appears to hang indefinitely, the most common culprits are improper done() callback invocation or missing promise returns. This diagnostic guide walks through recognizing the condition and applying targeted fixes.

Recognizable Condition

• Test runner stops responding after an async test starts
• Console shows no failures but test never progresses
• Timeout errors appear after 5+ seconds (Jasmine's default)
• Subsequent tests in the same describe block don't execute

Diagnostic Table: Common Causes and Their Signatures

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Symptom	Root Cause	Diagnostic Check
Test hangs, no completion message	done() never called	Search for done parameter in test function but no invocation
Async test passes but suite stops	Promise not returned	Check if async function returns a promise without return statement
Intermittent failures with setTimeout	Callback timing race condition	Verify done() called inside callback, not outside
Spies report calls from previous tests	State leakage between tests	Check for missing spy.cleartAllCalls() in afterEach

Ordered Diagnostic Checks

1. Identify async pattern used: Determine if the test uses done() callback or returns a promise.
2. Verify done() invocation: If using done parameter, confirm it's called exactly once at the end of async operation.
3. Check promise return: If returning a promise, ensure it's explicitly returned, not just passed as argument.
4. Examine setTimeout usage: Confirm done() is called inside the timeout callback, not before it.
5. Validate spy cleanup: Ensure spies are reset in afterEach to prevent cross-test contamination.

Concrete Example: Fixing a Hanging Test

Problematic code:

it('fetches user data', function(done) {
  fetch('/api/user/1')
    .then(response => response.json())
    .then(data => {
      expect(data.name).toBe('John');n    });
  // done() never called - test hangs
});

Fixed version:

it('fetches user data', function(done) {
  fetch('/api/user/1')
    .then(response => response.json())
    .then(data => {
      expect(data.name).toBe('John');n      done(); // Signal completion
    });
});

Alternative with promise return:

it('fetches user data', function() {
  return fetch('/api/user/1')
    .then(response => response.json())
    .then(data => {
      expect(data.name).toBe('John');
    });
});

Verification Steps

1. Run the specific test file: npx jasmine spec/async-test.spec.js --timeout=10000
2. Observe that test completes within expected time
3. Check that subsequent tests execute normally
4. Verify no state leakage in spy-based tests

Limitations and Important Notes

• done() must be called exactly once; calling it multiple times throws an error
• Promise-based async tests cannot use done() parameter - choose one pattern only
• Jasmine 2.x and later handle async differently than early versions; ensure version compatibility
• beforeEach/afterEach with async operations require the same patterns as it blocks

Escalation Criteria

If the above checks don't resolve the hanging issue, escalate to:

1. Check for unhandled promise rejections in the test output
2. Verify Jasmine configuration timeout setting (jasmine.DEFAULT_TIMEOUT_INTERVAL)
3. Consider using fail() explicitly in error handlers to surface silent failures
4. Review test framework integration (e.g., Karma, Jasmine CLI) for configuration issues