feat: implement stability fixes and enhance error handling

src/tests/unit/retry-utils.test.ts

@@ -0,0 +1,59 @@
+import { describe, it, expect } from 'vitest';
+import { applyJitter, calculateRetryDelay } from '../../lib/antigravity/retry-utils';
+
+describe('applyJitter', () => {
+  it('should return values within ±20% range', () => {
+    const baseDelay = 1000;
+    const results: number[] = [];
+
+    for (let i = 0; i < 100; i++) {
+      results.push(applyJitter(baseDelay));
+    }
+
+    // All values should be within 800-1200 range (±20%)
+    results.forEach((r) => {
+      expect(r).toBeGreaterThanOrEqual(800);
+      expect(r).toBeLessThanOrEqual(1200);
+    });
+  });
+
+  it('should produce different values (randomness)', () => {
+    const results = new Set<number>();
+    for (let i = 0; i < 20; i++) {
+      results.add(applyJitter(1000));
+    }
+    // 20 calls should produce multiple distinct values
+    expect(results.size).toBeGreaterThan(5);
+  });
+
+  it('should guarantee minimum value of 1 for small inputs', () => {
+    expect(applyJitter(1)).toBeGreaterThanOrEqual(1);
+    expect(applyJitter(0)).toBe(1);
+  });
+});
+
+describe('calculateRetryDelay', () => {
+  it('should implement exponential backoff', () => {
+    // First attempt (index 0): 1s ± 20% = 800-1200ms
+    const delay0 = calculateRetryDelay(0);
+    expect(delay0).toBeGreaterThanOrEqual(800);
+    expect(delay0).toBeLessThanOrEqual(1200);
+
+    // Second attempt (index 1): 2s ± 20% = 1600-2400ms
+    const delay1 = calculateRetryDelay(1);
+    expect(delay1).toBeGreaterThanOrEqual(1600);
+    expect(delay1).toBeLessThanOrEqual(2400);
+  });
+
+  it('should have maximum delay limit', () => {
+    // Even with high retry count, should not exceed 30s + 20% jitter = 36s
+    const delay = calculateRetryDelay(10);
+    expect(delay).toBeLessThanOrEqual(36000);
+  });
+
+  it('should accept custom base delay', () => {
+    const delay = calculateRetryDelay(0, 500);
+    expect(delay).toBeGreaterThanOrEqual(400); // 500 - 20%
+    expect(delay).toBeLessThanOrEqual(600); // 500 + 20%
+  });
+});