6.6Feature Flags as a Testing Strategy

Feature flags decouple deployment from release. You deploy the code but keep new features hidden behind flags, then enable them gradually.

// Feature flag check in application code
if (featureFlags.isEnabled('new-checkout-flow', { userId })) {
  return newCheckoutFlow();
} else {
  return legacyCheckoutFlow();
}

QA implications of feature flags:

• Test both states of every flag (enabled and disabled)
• Test flag combinations if features interact
• Verify that disabling a flag cleanly reverts to the old behavior
• Clean up old flags -- stale flags create technical debt and increase test complexity

// Test both flag states
test('checkout flow with new feature enabled', async () => {
  await setFeatureFlag('new-checkout-flow', true);
  // ... test new behavior
});

test('checkout flow with new feature disabled', async () => {
  await setFeatureFlag('new-checkout-flow', false);
  // ... test legacy behavior
});