如何编写用于角反应形式的自定义验证器的单元测试用例? [英] How to write a unit test case for a custom validator for angular reactive forms?

问题描述

我有一个自定义模型驱动的表单验证器，用于验证最大文本长度

I have a custom model-driven form validator to validate maximum text length

export function maxTextLength(length: string) {
  return function (control: FormControl) {
    const maxLenghtAllowed: number = +length;
    let value: string = control.value;
    if (value !== '' && value != null) {
      value = value.trim();
    }

    if (value != null && value.length > maxLenghtAllowed) {
      return { maxTextLength: true };
    }else {
      return null;
    }
  }
}

如何从中编写单元测试用例?

How to write a unit test case form this?

推荐答案

下面是受Subashan的回答启发的一个示例，该示例概述了基本过程:

Here's an example inspired by Subashan's answer which outlines the basic procedure:

import { maxTextLength } from '...';

describe('maxTextLength', () => {
  const maxTextLengthValidator = maxTextLength(10);
  const control = new FormControl('input');

  it('should return null if input string length is less than max', () => {
    control.setValue('12345');
    expect(maxLengthValidator(control)).toBeNull();
  });

  it('should return correct object if input string length is more than max', () => {
    control.setValue('12345678901');
    expect(maxLengthValidator(control)).toEqual({ maxTextLength: true });
  });
});

我还没有测试它，但是它与我写的东西相似，并且显示了基本方法.

I haven't tested it but it's similar to something I've written and it shows the basic approach.

我建议将验证器参数类型更改为 number :

I would recommend changing validator parameter type to number:

export function maxTextLength(length: number) {

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