NodeJS - 在回调过程中的Jest单元测试setTimeout

Question

我试图在我的process.on('SIGTERM')回调中使用Jest对一个计时器进行单元测试,但似乎从未调用过.我正在使用jest.useFakeTimers(),虽然它似乎模拟了setTimeout对某个范围的调用,但它setTimeout.mock在检查时并不会在对象中结束.

我的index.js文件:

process.on('SIGTERM', () => {
    console.log('Got SIGTERM');

    setTimeout(() => {
        console.log('Timer was run');
    }, 300);
});

setTimeout(() => {
    console.log('Timer 2 was run');
}, 30000);

和测试文件:

describe('Test process SIGTERM handler', () => {
    test.only('runs timeout', () => {
        jest.useFakeTimers();
        process.exit = jest.fn();

        require('./index.js');

        process.kill(process.pid, 'SIGTERM');

        jest.runAllTimers();

        expect(setTimeout.mock.calls.length).toBe(2);
    });
});

并且测试失败:

预期值为(使用===):2已接收:1且控制台日志输出为:

console.log tmp/index.js:10
    Timer 2 was run

  console.log tmp/index.js:2
    Got SIGTERM

如何setTimeout在这里运行？

Answer 1

可以做的是模拟进程on方法以确保您的处理程序将在kill方法上被调用。

确保将调用处理程序的一种方法是kill与on.

describe('Test process SIGTERM handler', () => {
    test.only('runs timeout', () => {
        jest.useFakeTimers();

        processEvents = {};

        process.on = jest.fn((signal, cb) => {
          processEvents[signal] = cb;
        });

        process.kill = jest.fn((pid, signal) => {
            processEvents[signal]();
        });

        require('./index.js');

        process.kill(process.pid, 'SIGTERM');

        jest.runAllTimers();

        expect(setTimeout.mock.calls.length).toBe(2);
    });
});

另一种更通用的方法是在 asetTimeout和 test 中模拟处理程序，该处理程序已被调用，如下所示：

index.js

var handlers = require('./handlers');

process.on('SIGTERM', () => {
    console.log('Got SIGTERM');
    setTimeout(handlers.someFunction, 300);
});

handlers.js

module.exports = {
    someFunction: () => {}
};

index.spec.js

describe('Test process SIGTERM handler', () => {
    test.only('sets someFunction as a SIGTERM handler', () => {
        jest.useFakeTimers();

        process.on = jest.fn((signal, cb) => {
            if (signal === 'SIGTERM') {
                cb();
            }
        });

        var handlerMock = jest.fn();

        jest.setMock('./handlers', {
            someFunction: handlerMock
        });

        require('./index');

        jest.runAllTimers();

        expect(handlerMock).toHaveBeenCalledTimes(1);
    });
});