单元测试溶液：
route.js：

const express = require('express');
const router = express.Router();

router.get('', (req, res, next) => {
  try {
    res.status(200).render('../views/');
  } catch (error) {
    next(error);
  }
});

router.get('*', (req, res, next) => {
  try {
    res.status(404).render('../views/not-found');
  } catch (error) {
    next(error);
  }
});

module.exports = router;

字符串
route.test.js：

describe('64051580', () => {
  afterEach(() => {
    jest.resetModules();
    jest.restoreAllMocks();
  });
  it('should render views', () => {
    const express = require('express');
    const mRouter = { get: jest.fn() };
    jest.spyOn(express, 'Router').mockImplementationOnce(() => mRouter);
    const mReq = {};
    const mRes = { status: jest.fn().mockReturnThis(), render: jest.fn() };
    const mNext = jest.fn();
    mRouter.get.mockImplementation((path, callback) => {
      if (path === '') {
        callback(mReq, mRes, mNext);
      }
    });
    require('./route');
    expect(mRes.status).toBeCalledWith(200);
    expect(mRes.render).toBeCalledWith('../views/');
  });

  it('should handle error', () => {
    const express = require('express');
    const mRouter = { get: jest.fn() };
    jest.spyOn(express, 'Router').mockImplementationOnce(() => mRouter);
    const mReq = {};
    const mErr = new Error('parse');
    const mRes = {
      status: jest.fn().mockReturnThis(),
      render: jest.fn().mockImplementationOnce(() => {
        throw mErr;
      }),
    };
    const mNext = jest.fn();
    mRouter.get.mockImplementation((path, callback) => {
      if (path === '') {
        callback(mReq, mRes, mNext);
      }
    });
    require('./route');
    expect(mNext).toBeCalledWith(mErr);
  });

  it('should render 404 not found view', () => {
    const express = require('express');
    const mRouter = { get: jest.fn() };
    jest.spyOn(express, 'Router').mockImplementationOnce(() => mRouter);
    const mReq = {};
    const mRes = { status: jest.fn().mockReturnThis(), render: jest.fn() };
    const mNext = jest.fn();
    mRouter.get.mockImplementation((path, callback) => {
      if (path === '*') {
        callback(mReq, mRes, mNext);
      }
    });
    require('./route');
    expect(mRes.status).toBeCalledWith(404);
    expect(mRes.render).toBeCalledWith('../views/not-found');
  });
});

型
单元测试结果和覆盖率报告：

PASS  src/stackoverflow/64051580/route.test.js
  64051580
    ✓ should render views (656ms)
    ✓ should handle error (17ms)
    ✓ should render 404 not found view (16ms)

----------|----------|----------|----------|----------|-------------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files |    90.91 |      100 |      100 |    90.91 |                   |
 route.js |    90.91 |      100 |      100 |    90.91 |                16 |
----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       3 passed, 3 total
Snapshots:   0 total
Time:        4.28s, estimated 10s

型