Question

如何在玩笑中测试给定的默认参数值？

具有模块的示例：

// calculate.js
module.exports = (a, b = 3) => {
    return a + b;
}

或更复杂的功能模块。

module.exports = (string, blockSizeInBits = 32) => {
    if (string === undefined) {
        return new Error('String not defined.');
    }

    const pad  = blockSizeInBits - (string.length % blockSizeInBits);
    const result = string + String.fromCharCode(0).repeat(pad - 1) + String.fromCharCode(pad);

    return result;
};

Answer 1

测试用例的每个预期结果都是我们指定的，即我们预先设置了预期结果，测试代码实际返回的结果是否与预期结果一致，如果一致，则测试案例通过，否则失败。代码逻辑有问题。

此外，我们的测试数据和test double应该尽可能简单，这样我们就可以轻松推断出我们期望的结果

例如

calculate.js：

module.exports = (string, blockSizeInBits = 32) => {
  if (string === undefined) {
    return new Error('String not defined.');
  }

  const pad = blockSizeInBits - (string.length % blockSizeInBits);
  const result = string + String.fromCharCode(0).repeat(pad - 1) + String.fromCharCode(pad);
  
  return result;
};

calculate.test.js：

const calc = require('./calculate');

describe('57941350', () => {
  it('should return an error if string is undefined', () => {
    const actual = calc(undefined);
    expect(actual).toBeInstanceOf(Error);
    expect(actual.message).toBe('String not defined.');
  });
  it('should calculate the result with default block size in bits', () => {
    const testString = 'a'.repeat(32);
    const actual = calc(testString);
    expect(actual).toEqual(testString + '\u0000'.repeat(31) + ' ');
  });
  it('should calculate the result with passed block size in bits', () => {
    const testString = 'a';
    const actual = calc(testString, 1);
    expect(actual).toEqual('a\u0001');
  });
});

单元测试结果：

 PASS  examples/57941350/calculate.test.js
  57941350
    ✓ should return an error if string is undefined (1 ms)
    ✓ should calculate the result with default block size in bits (1 ms)
    ✓ should calculate the result with passed block size in bits

--------------|---------|----------|---------|---------|-------------------
File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
--------------|---------|----------|---------|---------|-------------------
All files     |     100 |      100 |     100 |     100 |                   
 calculate.js |     100 |      100 |     100 |     100 |                   
--------------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       3 passed, 3 total
Snapshots:   0 total
Time:        4.849 s

如何在Jest中测试es6默认值

1 个答案: