typescript - 如何期望字符串以指定的变量开头

Question

我有一个从复杂对象构造字符串的简单函数。为了简单起见，我会这样做

public generateMessage(property: string): string {
    return `${property} more text.`;
}

我的测试目前是

    it('starts the message with the property name', () => {
        const property = 'field';
        const message: string = myClass.generateMessage(property);

        expect(message).toEqual(`${property} more text.`);
    });

这里唯一相关的是生成的消息以属性开头。有没有办法可以检查字符串是否以该属性开头？伪代码:
expect(message).toStartWith(property);
还是我必须使用 startsWith() 自己做字符串的方法？目前我想到的最佳解决方案是

expect(message.startsWith(property)).toBeTruthy();

Answer 1

您可以使用 .toMatch(regexpOrString)和正则表达式来做到这一点。正则表达式模式等价于 startsWith是 /^field?/
例如。
index.ts :

class MyClass {
  public generateMessage(property: string): string {
    return `${property} more text.`;
  }
}

export { MyClass };

index.test.ts :

import { MyClass } from './';

describe('61290819', () => {
  it('should pass', () => {
    const myClass = new MyClass();
    const property = 'field';
    const message: string = myClass.generateMessage(property);
    expect(message).toMatch(new RegExp(`^${property}?`));
  });

  it('should pass too', () => {
    const myClass = new MyClass();
    const property = 'f_ield'; // make some changes
    const message: string = myClass.generateMessage(property);
    expect(message).not.toMatch(new RegExp('^field?'));
  });
});

单元测试结果:

 PASS  stackoverflow/61290819/index.test.ts (9.814s)
  61290819
    ✓ should pass (5ms)
    ✓ should not pass

Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        11.417s