Add unit tests for circuit-breaker module

tests/core/ids/circuit-breaker.test.js

@@ -0,0 +1,252 @@
+/**
+ * Unit tests for circuit-breaker module
+ *
+ * Tests the CircuitBreaker pattern implementation with
+ * CLOSED, OPEN, and HALF_OPEN states.
+ */
+
+const {
+  CircuitBreaker,
+  STATE_CLOSED,
+  STATE_OPEN,
+  STATE_HALF_OPEN,
+  DEFAULT_FAILURE_THRESHOLD,
+  DEFAULT_SUCCESS_THRESHOLD,
+  DEFAULT_RESET_TIMEOUT_MS,
+} = require('../../../.aios-core/core/ids/circuit-breaker');
+
+describe('CircuitBreaker', () => {
+  let breaker;
+
+  beforeEach(() => {
+    breaker = new CircuitBreaker();
+  });
+
+  // ============================================================
+  // Constants
+  // ============================================================
+  describe('constants', () => {
+    test('state constants are defined', () => {
+      expect(STATE_CLOSED).toBe('CLOSED');
+      expect(STATE_OPEN).toBe('OPEN');
+      expect(STATE_HALF_OPEN).toBe('HALF_OPEN');
+    });
+
+    test('default thresholds are defined', () => {
+      expect(DEFAULT_FAILURE_THRESHOLD).toBe(5);
+      expect(DEFAULT_SUCCESS_THRESHOLD).toBe(3);
+      expect(DEFAULT_RESET_TIMEOUT_MS).toBe(60000);
+    });
+  });
+
+  // ============================================================
+  // Constructor
+  // ============================================================
+  describe('constructor', () => {
+    test('starts in CLOSED state', () => {
+      expect(breaker.getState()).toBe(STATE_CLOSED);
+    });
+
+    test('uses default thresholds', () => {
+      const stats = breaker.getStats();
+      expect(stats.failureCount).toBe(0);
+      expect(stats.successCount).toBe(0);
+      expect(stats.totalTrips).toBe(0);
+    });
+
+    test('accepts custom options', () => {
+      const custom = new CircuitBreaker({
+        failureThreshold: 3,
+        successThreshold: 2,
+        resetTimeoutMs: 30000,
+      });
+      // Trip it to verify custom threshold
+      for (let i = 0; i < 3; i++) custom.recordFailure();
+      expect(custom.getState()).toBe(STATE_OPEN);
+    });
+  });
+
+  // ============================================================
+  // isAllowed
+  // ============================================================
+  describe('isAllowed', () => {
+    test('allows requests when CLOSED', () => {
+      expect(breaker.isAllowed()).toBe(true);
+    });
+
+    test('blocks requests when OPEN', () => {
+      // Trip the breaker
+      for (let i = 0; i < 5; i++) breaker.recordFailure();
+      expect(breaker.getState()).toBe(STATE_OPEN);
+      expect(breaker.isAllowed()).toBe(false);
+    });
+
+    test('transitions to HALF_OPEN after reset timeout', () => {
+      for (let i = 0; i < 5; i++) breaker.recordFailure();
+      expect(breaker.getState()).toBe(STATE_OPEN);
+
+      // Simulate timeout passing
+      breaker._lastFailureTime = Date.now() - 61000;
+
+      expect(breaker.isAllowed()).toBe(true);
+      expect(breaker.getState()).toBe(STATE_HALF_OPEN);
+    });
+
+    test('allows one probe in HALF_OPEN', () => {
+      breaker._state = STATE_HALF_OPEN;
+      breaker._halfOpenProbeInFlight = false;
+
+      expect(breaker.isAllowed()).toBe(true);
+      expect(breaker.isAllowed()).toBe(false); // second request blocked
+    });
+  });
+
+  // ============================================================
+  // recordSuccess
+  // ============================================================
+  describe('recordSuccess', () => {
+    test('resets failure count in CLOSED state', () => {
+      breaker.recordFailure();
+      breaker.recordFailure();
+      expect(breaker.getStats().failureCount).toBe(2);
+
+      breaker.recordSuccess();
+      expect(breaker.getStats().failureCount).toBe(0);
+    });
+
+    test('counts successes in HALF_OPEN', () => {
+      breaker._state = STATE_HALF_OPEN;
+      breaker._halfOpenProbeInFlight = true;
+
+      breaker.recordSuccess();
+      expect(breaker.getStats().successCount).toBe(1);
+    });
+
+    test('closes circuit after success threshold in HALF_OPEN', () => {
+      breaker._state = STATE_HALF_OPEN;
+
+      for (let i = 0; i < 3; i++) {
+        breaker._halfOpenProbeInFlight = true;
+        breaker.recordSuccess();
+      }
+
+      expect(breaker.getState()).toBe(STATE_CLOSED);
+      expect(breaker.getStats().failureCount).toBe(0);
+      expect(breaker.getStats().successCount).toBe(0);
+    });
+  });
+
+  // ============================================================
+  // recordFailure
+  // ============================================================
+  describe('recordFailure', () => {
+    test('increments failure count', () => {
+      breaker.recordFailure();
+      expect(breaker.getStats().failureCount).toBe(1);
+    });
+
+    test('opens circuit at threshold', () => {
+      for (let i = 0; i < 4; i++) breaker.recordFailure();
+      expect(breaker.getState()).toBe(STATE_CLOSED);
+
+      breaker.recordFailure(); // 5th failure
+      expect(breaker.getState()).toBe(STATE_OPEN);
+    });
+
+    test('increments totalTrips when opening', () => {
+      for (let i = 0; i < 5; i++) breaker.recordFailure();
+      expect(breaker.getStats().totalTrips).toBe(1);
+    });
+
+    test('re-opens circuit from HALF_OPEN on failure', () => {
+      breaker._state = STATE_HALF_OPEN;
+      breaker._halfOpenProbeInFlight = true;
+
+      breaker.recordFailure();
+
+      expect(breaker.getState()).toBe(STATE_OPEN);
+      expect(breaker.getStats().totalTrips).toBe(1);
+    });
+
+    test('records lastFailureTime', () => {
+      const before = Date.now();
+      breaker.recordFailure();
+      const after = Date.now();
+
+      expect(breaker.getStats().lastFailureTime).toBeGreaterThanOrEqual(before);
+      expect(breaker.getStats().lastFailureTime).toBeLessThanOrEqual(after);
+    });
+  });
+
+  // ============================================================
+  // getStats
+  // ============================================================
+  describe('getStats', () => {
+    test('returns complete stats object', () => {
+      const stats = breaker.getStats();
+
+      expect(stats).toHaveProperty('state');
+      expect(stats).toHaveProperty('failureCount');
+      expect(stats).toHaveProperty('successCount');
+      expect(stats).toHaveProperty('totalTrips');
+      expect(stats).toHaveProperty('lastFailureTime');
+    });
+
+    test('lastFailureTime is null initially', () => {
+      expect(breaker.getStats().lastFailureTime).toBeNull();
+    });
+  });
+
+  // ============================================================
+  // reset
+  // ============================================================
+  describe('reset', () => {
+    test('resets to CLOSED state', () => {
+      for (let i = 0; i < 5; i++) breaker.recordFailure();
+      expect(breaker.getState()).toBe(STATE_OPEN);
+
+      breaker.reset();
+
+      expect(breaker.getState()).toBe(STATE_CLOSED);
+      expect(breaker.getStats().failureCount).toBe(0);
+      expect(breaker.getStats().successCount).toBe(0);
+    });
+  });
+
+  // ============================================================
+  // Full lifecycle
+  // ============================================================
+  describe('full lifecycle', () => {
+    test('CLOSED -> OPEN -> HALF_OPEN -> CLOSED', () => {
+      // 1. Start CLOSED
+      expect(breaker.getState()).toBe(STATE_CLOSED);
+
+      // 2. Trip to OPEN
+      for (let i = 0; i < 5; i++) breaker.recordFailure();
+      expect(breaker.getState()).toBe(STATE_OPEN);
+
+      // 3. Wait and transition to HALF_OPEN
+      breaker._lastFailureTime = Date.now() - 61000;
+      breaker.isAllowed();
+      expect(breaker.getState()).toBe(STATE_HALF_OPEN);
+
+      // 4. Success probe closes circuit
+      breaker.recordSuccess();
+      breaker._halfOpenProbeInFlight = true;
+      breaker.recordSuccess();
+      breaker._halfOpenProbeInFlight = true;
+      breaker.recordSuccess();
+      expect(breaker.getState()).toBe(STATE_CLOSED);
+    });
+
+    test('CLOSED -> OPEN -> HALF_OPEN -> OPEN (failure in half-open)', () => {
+      for (let i = 0; i < 5; i++) breaker.recordFailure();
+      breaker._lastFailureTime = Date.now() - 61000;
+      breaker.isAllowed(); // HALF_OPEN
+
+      breaker.recordFailure(); // re-opens
+      expect(breaker.getState()).toBe(STATE_OPEN);
+      expect(breaker.getStats().totalTrips).toBe(2);
+    });
+  });
+});