如何在 Jest 中的 beforeAll / beforeEach 和测试之间共享数据？

我们使用 jest 来测试我们的 API，并且有相当复杂的场景。我们使用beforeAll函数为每个测试设置通用辅助变量，有时设置租户分离，在其他情况下我们使用beforeEach为测试设置租户分离的函数，并为测试租户提供一些默认配置，...

例如，测试可能像这样（如您所见，我们使用 TypeScript 来编写测试，以防万一）：

let apiClient: ApiClient;
let tenantId: string;

beforeAll(async () => {
    apiClient = await getClientWithCredentials();
});

beforeEach(async () => {
    tenantId = await createNewTestTenant();
});

describe('describing complex test scenario', () => {
    it('should have some initial state', async () => {
        await checkState(tenantId);
    });

    it('should have some state after performing op1', async () =>{
        await op1(tenantId);
        await checkStateAfterOp1(tenantId);
    });

    it('should have some state after performing op2', async () =>{
        await op2(tenantId);
        await checkStateAfterOp2(tenantId);
    });

    it('should have some state after performing op1 and op2', async () =>{
        await op1(tenantId);
        await op2(tenantId);
        await checkStateAfterOp1AndOp2(tenantId);
    });

    it('the order of op1 and op2 should not matter', async () =>{
        await op2(tenantId);
        await op1(tenantId);
        await checkStateAfterOp1AndOp2(tenantId);
    });    
});

describe('another similar complex scenario', () => {
    // ... you see where this is going
});

问题是，共享这些初始化的变量的最佳方式是什么beforeAll and beforeEach？ - 如果使用以下命令执行上述测试，则​​有效--runInBand选项，其中“...在当前进程中串行运行所有测试...”

但当并行执行时，它开始随机失败，主要是指tenantId未定义。鉴于这些测试是 ~200 个类似测试的一部分，因此全部都通过了。同时，这取决于机器。具有 8 核/16 线程的构建代理只有 50-60% 通过测试。我使用四核 CPU 的同事大约有 80% 通过了测试，而对于使用双核 CPU 的我来说，有时只有 1-2 个测试失败，其他时候大约有 10 个测试失败。显然这取决于并行度。

我发现了 2 个 GitHub 问题，人们提到了使用的可能性this共享上下文（不再起作用）或将所有内容封装在describe:

• https://github.com/facebook/jest/issues/3553 https://github.com/facebook/jest/issues/3553
• https://github.com/facebook/jest/issues/3673 https://github.com/facebook/jest/issues/3673

所以我尝试了一个非常幼稚的方法：

describe('tests', () => {
    let apiClient: ApiClient;
    let tenantId: string;

    beforeAll(async () => {
        apiClient = await getClientWithCredentials();
    });

    beforeEach(async () => {
        tenantId = await createNewTestTenant();
    });

    describe('describing complex test scenario', () => {
        it('should have some initial state', async () => {
            await checkState(tenantId);
        });

        it('should have some state after performing op1', async () =>{
            await op1(tenantId);
            await checkStateAfterOp1(tenantId);
        });

        it('should have some state after performing op2', async () =>{
            await op2(tenantId);
            await checkStateAfterOp2(tenantId);
        });

        it('should have some state after performing op1 and op2', async () =>{
            await op1(tenantId);
            await op2(tenantId);
            await checkStateAfterOp1AndOp2(tenantId);
        });

        it('the order of op1 and op2 should not matter', async () =>{
            await op2(tenantId);
            await op1(tenantId);
            await checkStateAfterOp1AndOp2(tenantId);
        });    
    });

    describe('another similar complex scenario', () => {
        // ... you see where this is going
    });
});

但这似乎并没有任何效果。 我真的很想并行运行测试，但我在文档中找不到任何相关内容。也许我不知道我应该寻找什么？

这对你有用吗？

describe('tests', () => {
    let apiClient: ApiClient;
    let tenantIds: {id: string, used: boolean}[];

    const findUnusedTenantId = () => {
      const tenant = tenantIds.find(a => !a.used);
      tenant.used = true; 
      return tenant.id
    }

    beforeAll(async () => {
        apiClient = await getClientWithCredentials();
    });

    beforeEach(async () => {
        const id = await createNewTestTenant();
        tenantIds.push({id, used: false})
    });

    describe('describing complex test scenario', () => {
        let tenantId: string
        it('should have some initial state', async () => {
            tenantId = fineUnusedTenantId();
            await checkState(tenantId);
        });

        it('should have some state after performing op1', async () =>{
            await op1(tenantId);
            await checkStateAfterOp1(tenantId);
        });

        // ...
    });
    describe('next scenario', () => {
        let tenantId: string
        it('first test', async () => {
            tenantId = fineUnusedTenantId();
            await checkState(tenantId);
        });

你可能想要一个 afterAll 钩子来清理数据库