如何用Jest测试void方法

问题描述

我想测试记录器是否正确增加（使用Jest）。查看下面的代码，这意味着我想检查增量(1)（意味着空白myMethod的内容）是否正在被调用。

// myScript.ts
import dd from 'datadog-metrics';

export class MyClass { 
    private bufferedMetricslogger: dd.BufferedMetricslogger; 

    constructor(bufferedMetricslogger: dd.BufferedMetricslogger) { 
        this.bufferedMetricslogger = bufferedMetricslogger; 
    } 

    public myMethod(myInput: String): void { 
        this.bufferedMetricslogger.increment('my.key.name',1,[`mytag:${myInput}`]);  // (1)
    }
}

// myScript.test.ts
import { mock,instance,verify } from 'ts-mockito'; 
import { BufferedMetricslogger } from 'datadog-metrics'; 
import { myClass } from 'path/to/myScript'; 

describe('Testing MyClass',() => { 
    it('verify that myMethod increments',() => { 
        const mockedBufferedMetricslogger: BufferedMetricslogger = mock(BufferedMetricslogger); 
        const bufferedMetricslogger:       BufferedMetricslogger = instance(mockedBufferedMetricslogger); 

        const mockMyClass: MyClass    = mock(MyClass); 
        const myClassOption1: MyClass = instance(mockMyClass); 
        const myClassOption2: MyClass = new MyClass(mockedBufferedMetricslogger); 

        myClassOption1.myMethod('XXX');                                       // Option 1
        myClassOption2.myMethod('XXX');                                       // Option 2
        bufferedMetricslogger.increment('my.key.name',[`mytag:${XXX}`]);  // Option 3
        verify(mockedBufferedMetricslogger.increment('my.key.name',[`mytag:${XXX}`])).once();
    })
}); 

我尝试了三种不同的Option。每个Option都会产生一条消息

Expected "increment(strictEqual(my.key.name)",strictEqual(1),strichtEqual([mytag:XXX]))" to be called 1 time(s). But has been called 0 time(s). 

实际上，我想要的是Option 1或Option 2。对于Option 3，我只是尝试了一下，因为我认为这肯定可以。

有人可以帮我吗？

谢谢。

解决方法

您的代码中的问题在于，您正在传递一个数组作为第三个参数，并且，如您在返回的消息中看到的那样，它正在尝试使用strictEqual（===）对其进行检查。您可以使用嘲笑提供的deepEqual函数来获得所需的结果。

verify(mockedBufferedMetricsLogger.increment('my.key.name',1,deepEqual([`myTag:${XXX}`]))).once();

并确保您正确地处理了参数，因为我不得不稍微更改代码以使其起作用。这是我完整的工作代码：

// myScript.ts
import { BufferedMetricsLogger } from 'datadog-metrics';

export class MyClass { 
    private bufferedMetricsLogger: BufferedMetricsLogger; 

    constructor(bufferedMetricsLogger: BufferedMetricsLogger) { 
        this.bufferedMetricsLogger = bufferedMetricsLogger; 
    } 

    public myMethod(myInput: String): void {
        this.bufferedMetricsLogger.increment('my.key.name',[`myTag:${myInput}`]);  // (1)
    }
}


// myScript.test.ts
import { mock,instance,verify,deepEqual } from 'ts-mockito'; 
import { BufferedMetricsLogger } from 'datadog-metrics'; 
import { MyClass } from './myScript'; 

describe('Testing MyClass',() => { 
    it('verify that myMethod increments',() => { 
        const mockedBufferedMetricsLogger: BufferedMetricsLogger = mock(BufferedMetricsLogger);
        const bufferedMetricsLogger:       BufferedMetricsLogger = instance(mockedBufferedMetricsLogger); 

        const myClassOption1 = new MyClass(bufferedMetricsLogger);
        // const bufferedMetricsLogger:       BufferedMetricsLogger = instance(mockedBufferedMetricsLogger); 

        // const mockMyClass: MyClass    = mock(MyClass); 
        // const myClassOption1: MyClass = instance(mockMyClass); 
        // const myClassOption2: MyClass = new MyClass(mockedBufferedMetricsLogger); 

        myClassOption1.myMethod('XXX');                                       // Option 1
        // myClassOption2.myMethod('XXX');                                       // Option 2
        // bufferedMetricsLogger.increment('my.key.name',[`myTag:XXX`]);  // Option 3
        verify(mockedBufferedMetricsLogger.increment('my.key.name',deepEqual([`myTag:XXX`]))).once();
    })
});