mergeConfig 模块单元测试

合并配置是 ts-axios 核心流程中非常重要的一个环节，我们需要为它的各种情况去编写测试。

测试代码编写

test/mergeConfig.spec.ts：

import axios from '../src/index'
import mergeConfig from '../src/core/mergeConfig'

describe('mergeConfig', () => {
  const defaults = axios.defaults

  test('should accept undefined for second argument', () => {
    expect(mergeConfig(defaults, undefined)).toEqual(defaults)
  })

  test('should accept an object for second argument', () => {
    expect(mergeConfig(defaults, {})).toEqual(defaults)
  })

  test('should not leave references', () => {
    const merged = mergeConfig(defaults, {})
    expect(merged).not.toBe(defaults)
    expect(merged.headers).not.toBe(defaults.headers)
  })

  test('should allow setting request options', () => {
    const config = {
      url: '__sample url__',
      params: '__sample params__',
      data: { foo: true }
    }
    const merged = mergeConfig(defaults, config)
    expect(merged.url).toBe(config.url)
    expect(merged.params).toBe(config.params)
    expect(merged.data).toEqual(config.data)
  })

  test('should not inherit request options', () => {
    const localDefaults = {
      url: '__sample url__',
      params: '__sample params__',
      data: { foo: true }
    }
    const merged = mergeConfig(localDefaults, {})
    expect(merged.url).toBeUndefined()
    expect(merged.params).toBeUndefined()
    expect(merged.data).toBeUndefined()
  })

  test('should return default headers if pass config2 with undefined', () => {
    expect(
      mergeConfig(
        {
          headers: 'x-mock-header'
        },
        undefined
      )
    ).toEqual({
      headers: 'x-mock-header'
    })
  })

  test('should merge auth, headers with defaults', () => {
    expect(
      mergeConfig(
        {
          auth: undefined
        },
        {
          auth: {
            username: 'foo',
            password: 'test'
          }
        }
      )
    ).toEqual({
      auth: {
        username: 'foo',
        password: 'test'
      }
    })
    expect(
      mergeConfig(
        {
          auth: {
            username: 'foo',
            password: 'test'
          }
        },
        {
          auth: {
            username: 'baz',
            password: 'foobar'
          }
        }
      )
    ).toEqual({
      auth: {
        username: 'baz',
        password: 'foobar'
      }
    })
  })

  test('should overwrite auth, headers with a non-object value', () => {
    expect(
      mergeConfig(
        {
          headers: {
            common: {
              Accept: 'application/json, text/plain, */*'
            }
          }
        },
        {
          headers: null
        }
      )
    ).toEqual({
      headers: null
    })
  })

  test('should allow setting other options', () => {
    const merged = mergeConfig(defaults, {
      timeout: 123
    })
    expect(merged.timeout).toBe(123)
  })
})

运行测试后我们发现 mergeConfig.ts 文件的分支覆盖率并未达到 100%，提示是 23 行，打开文件后发现最后一个 else 逻辑并未走到，也就是 val1 为 undefined 的情况。但实际上即使 val1 为 undefined，我们也是返回 undefined，也就是返回 val1，所以这块代码的逻辑可以优化。

function deepMergeStrat(val1: any, val2: any): any {
  if (isPlainObject(val2)) {
    return deepMerge(val1, val2)
  } else if (typeof val2 !== 'undefined') {
    return val2
  } else if (isPlainObject(val1)) {
    return deepMerge(val1)
  } else {
    return val1
  }
}

2 个分支可以合并到一个分支，这样我们再次跑测试，分支覆盖率就可以达到 100% 了。

至此我们完成了 ts-axios 库对 mergeConfig 模块的测试，下一节课我们来测试取消模块相关代码。