🧪 Add tests for isInRollout algorithm (#544)

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: sunnylqm <615282+sunnylqm@users.noreply.github.com>

Author: sunnylqm

src/__tests__/isInRollout.test.ts

@@ -0,0 +1,85 @@
+import { describe, expect, it, mock } from 'bun:test';
+
+// Use the preload setup file instead of inline mocks since bun resolves
+// dynamic imports relative to the test runner's context and caching.
+import './setup';
+
+let mockUuid = '';
+mock.module('../core', () => {
+  return {
+    cInfo: {
+      get uuid() { return mockUuid; }
+    }
+  };
+});
+
+import { murmurhash3_32_gc } from '../isInRollout';
+
+describe('murmurhash3_32_gc', () => {
+  it('should be deterministic (return the same output for the same input)', () => {
+    const input1 = '123e4567-e89b-12d3-a456-426614174000';
+    const input2 = 'test-string';
+
+    expect(murmurhash3_32_gc(input1)).toBe(murmurhash3_32_gc(input1));
+    expect(murmurhash3_32_gc(input2)).toBe(murmurhash3_32_gc(input2));
+  });
+
+  it('should return different outputs for different inputs', () => {
+    const input1 = '123e4567-e89b-12d3-a456-426614174000';
+    const input2 = '123e4567-e89b-12d3-a456-426614174001';
+
+    expect(murmurhash3_32_gc(input1)).not.toBe(murmurhash3_32_gc(input2));
+  });
+
+  it('should handle empty string correctly', () => {
+    expect(typeof murmurhash3_32_gc('')).toBe('number');
+  });
+
+  it('should return known outputs for known inputs', () => {
+    expect(murmurhash3_32_gc('test1') % 100).toBe(24);
+    expect(murmurhash3_32_gc('test2') % 100).toBe(69);
+    expect(murmurhash3_32_gc('test3') % 100).toBe(0);
+    expect(murmurhash3_32_gc('123e4567-e89b-12d3-a456-426614174000') % 100).toBe(36);
+    expect(murmurhash3_32_gc('123e4567-e89b-12d3-a456-426614174001') % 100).toBe(94);
+  });
+});
+
+describe('isInRollout', () => {
+  it('should return true when the rollout is greater than the hash modulo', async () => {
+    mockUuid = 'test1';
+    const { isInRollout } = await import(`../isInRollout?id=${Date.now()}`);
+    expect(isInRollout(25)).toBe(true);
+  });
+
+  it('should return false when the rollout is equal to the hash modulo', async () => {
+    mockUuid = 'test1';
+    const { isInRollout } = await import(`../isInRollout?id=${Date.now()}`);
+    expect(isInRollout(24)).toBe(false);
+  });
+
+  it('should return false when the rollout is less than the hash modulo', async () => {
+    mockUuid = 'test1';
+    const { isInRollout } = await import(`../isInRollout?id=${Date.now()}`);
+    expect(isInRollout(23)).toBe(false);
+  });
+
+  it('should evaluate correctly for a different uuid', async () => {
+    mockUuid = 'test3';
+    const { isInRollout } = await import(`../isInRollout?id=${Date.now()}`);
+    expect(isInRollout(1)).toBe(true);
+    expect(isInRollout(0)).toBe(false);
+    expect(isInRollout(-1)).toBe(false);
+  });
+
+  it('should always return false for 0% rollout', async () => {
+    mockUuid = 'test1';
+    const { isInRollout } = await import(`../isInRollout?id=${Date.now()}`);
+    expect(isInRollout(0)).toBe(false);
+  });
+
+  it('should always return true for 100% rollout', async () => {
+    mockUuid = 'test1';
+    const { isInRollout } = await import(`../isInRollout?id=${Date.now()}`);
+    expect(isInRollout(100)).toBe(true);
+  });
+});

src/__tests__/setup.ts

@@ -38,3 +38,7 @@ mock.module('../i18n', () => {
     },
   };
 });
+
+mock.module('react-native/Libraries/Core/ReactNativeVersion', () => ({
+  version: { major: 0, minor: 73, patch: 0 },
+}));

src/isInRollout.ts

@@ -3,7 +3,7 @@
 import { cInfo } from './core';
 
 /* eslint-disable no-bitwise */
-function murmurhash3_32_gc(key: string, seed = 0) {
+export function murmurhash3_32_gc(key: string, seed = 0) {
   let remainder, bytes, h1, h1b, c1, c2, k1, i;
 
   remainder = key.length & 3; // key.length % 4