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：

  1. import axios from '../src/index'
  2. import mergeConfig from '../src/core/mergeConfig'
  4. describe('mergeConfig', () => {
  5.   const defaults = axios.defaults
  7.   test('should accept undefined for second argument', () => {
  8.     expect(mergeConfig(defaults, undefined)).toEqual(defaults)
  9.   })
  11.   test('should accept an object for second argument', () => {
  12.     expect(mergeConfig(defaults, {})).toEqual(defaults)
  13.   })
  15.   test('should not leave references', () => {
  16.     const merged = mergeConfig(defaults, {})
  17.     expect(merged).not.toBe(defaults)
  18.     expect(merged.headers).not.toBe(defaults.headers)
  19.   })
  21.   test('should allow setting request options', () => {
  22.     const config = {
  23.       url: '__sample url__',
  24.       params: '__sample params__',
  25.       data: { foo: true }
  26.     }
  27.     const merged = mergeConfig(defaults, config)
  28.     expect(merged.url).toBe(config.url)
  29.     expect(merged.params).toBe(config.params)
  30.     expect(merged.data).toEqual(config.data)
  31.   })
  33.   test('should not inherit request options', () => {
  34.     const localDefaults = {
  35.       url: '__sample url__',
  36.       params: '__sample params__',
  37.       data: { foo: true }
  38.     }
  39.     const merged = mergeConfig(localDefaults, {})
  40.     expect(merged.url).toBeUndefined()
  41.     expect(merged.params).toBeUndefined()
  42.     expect(merged.data).toBeUndefined()
  43.   })
  45.   test('should return default headers if pass config2 with undefined', () => {
  46.     expect(
  47.       mergeConfig(
  48.         {
  49.           headers: 'x-mock-header'
  50.         },
  51.         undefined
  52.       )
  53.     ).toEqual({
  54.       headers: 'x-mock-header'
  55.     })
  56.   })
  58.   test('should merge auth, headers with defaults', () => {
  59.     expect(
  60.       mergeConfig(
  61.         {
  62.           auth: undefined
  63.         },
  64.         {
  65.           auth: {
  66.             username: 'foo',
  67.             password: 'test'
  68.           }
  69.         }
  70.       )
  71.     ).toEqual({
  72.       auth: {
  73.         username: 'foo',
  74.         password: 'test'
  75.       }
  76.     })
  77.     expect(
  78.       mergeConfig(
  79.         {
  80.           auth: {
  81.             username: 'foo',
  82.             password: 'test'
  83.           }
  84.         },
  85.         {
  86.           auth: {
  87.             username: 'baz',
  88.             password: 'foobar'
  89.           }
  90.         }
  91.       )
  92.     ).toEqual({
  93.       auth: {
  94.         username: 'baz',
  95.         password: 'foobar'
  96.       }
  97.     })
  98.   })
  100.   test('should overwrite auth, headers with a non-object value', () => {
  101.     expect(
  102.       mergeConfig(
  103.         {
  104.           headers: {
  105.             common: {
  106.               Accept: 'application/json, text/plain, */*'
  107.             }
  108.           }
  109.         },
  110.         {
  111.           headers: null
  112.         }
  113.       )
  114.     ).toEqual({
  115.       headers: null
  116.     })
  117.   })
  119.   test('should allow setting other options', () => {
  120.     const merged = mergeConfig(defaults, {
  121.       timeout: 123
  122.     })
  123.     expect(merged.timeout).toBe(123)
  124.   })
  125. })

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。

  1. function deepMergeStrat(val1: any, val2: any): any {
  2.   if (isPlainObject(val2)) {
  3.     return deepMerge(val1, val2)
  4.   } else if (typeof val2 !== 'undefined') {
  5.     return val2
  6.   } else if (isPlainObject(val1)) {
  7.     return deepMerge(val1)
  8.   } else {
  9.     return val1
  10.   }
  11. }

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。