使用Jasmine测试Angular2/TypeScript管道

Question

我有一个带有TypeScript应用程序设置的Angular2,它具有非常基本的Jasmine测试.我想测试一下我的管道.

lpad.pipe.ts

import {Pipe, PipeTransform} from '@angular/core';
@Pipe({
    name: 'lpad'
})
export class LPadPipe implements PipeTransform {
    transform(value: any, args: string[]): any {
       let pad = args[0];
       return (pad + value).slice(-pad.length);
    }
}

在html模板中的用法:

{{size.SizeCode | lpad:['0000']}}

lpad.pipe.spec.ts - 我的测试(不起作用)

import { LPadPipe } from './lpad.pipe';

describe('LPadPipe'), () => {
    let pipe: LPadPipe;

    beforeEach(() => {
        pipe = new LPadPipe();
    });

    it('transforms "1" to "0001"', () => {
        let value: any = "1";
        let args: string[] = ['0000'];

        expect(pipe.transform(value, args)).ToEqual('0001')
    });

}

错误信息:

Error: TypeError: Cannot read property 'length' of undefined(…)

我认为问题在于我的测试的"价值"和"args".知道怎么解决？

Answer 1

这是因为您在使用该describe方法时遇到错误:

describe('LPadPipe'), () => { // <----------------
  let pipe: LPadPipe;

  beforeEach(() => {
    pipe = new LPadPipe();
  });

  it('transforms "1" to "0001"', () => {
    let value: any = "1";
    let args: string[] = ['0000'];

    expect(pipe.transform(value, args)).ToEqual('0001')
  });

} // <----------------

您应该使用以下代码:

describe('LPadPipe', () => { // <----------------
  let pipe: LPadPipe;

  beforeEach(() => {
    pipe = new LPadPipe();
  });

  it('transforms "1" to "0001"', () => {
    let value: any = "1";
    let args: string[] = ['0000'];

    expect(pipe.transform(value, args)).ToEqual('0001')
  });

}); // <----------------