javascript - Redux reducer 的分支覆盖率

Question

假设我有以下 reducer :

import {FOO} from '../const/Foo'

const myReducer = (initialState = {foo: ''}, action) => {
  const state = {}
  if (action) {
    switch (action.type) {
      case FOO:
        state.foo = action.foo
    };
  }
  return Object.assign({}, initialState, state)
}

我用 jest 测试:

import FOO from '../const/Foo'

test('returns correct state when action is not "Foo"', () => {
  expect(myReducer({foo: 'bar'}, {type: 'foo'})).toEqual({foo: 'bar'})
})

test("returns correct state when action is 'Foo'", () => {
  expect(myReducer({}, {type: FOO, foo: 'bar'})).toEqual({foo: 'bar'})
})

test('when there is no action / testing the default', () => {
  expect(myReducer()).toEqual({foo: ''})
})

这产生了 4/5 的分支覆盖率。经过一些思考/删除和/或重新添加行后，我得出了 initialState 集上的分支逻辑。这几乎是有道理的。除了:

1) 为什么最后一个测试，一个空的 myReducer() 调用没有涵盖这种情况。

当 reducer 被缩减为:

const myReducer = (initialState = {foo: ''}, action) => {
    const state = {}
    return Object.assign({}, initialState, state)
}

测试(现在失败了)的分支覆盖率为 1/1。

这是怎么回事？

编辑:根据要求，我正在添加配置。我将以下 jest.json 传递给 jest:

{

  "bail": true,
  "verbose": true,
  "moduleNameMapper": {
    "\\.(sass|jpg|png)$": "<rootDir>/src/main/js/config/emptyExport.js"
  },
  "testRegex": ".*(?<!snapshot)\\.(test|spec)\\.js$",
  "collectCoverage": true,
  "collectCoverageFrom": ["src/main/js/**/*.js"
    , "!**/node_modules/**"
    , "!**/*spec.js"
    , "!src/main/js/config/emptyExport.js"
    , "!**/coverage/**/*.js"
    , "!src/main/js/app.js"
    , "!src/main/js/store/configureStore.js"
    , "!src/main/js/reducers/index.js"],
  "coverageDirectory": "<rootDir>/src/main/js/coverage",
  "coverageThreshold": {
    "global": {
      "branches": 85,
      "function": 95,
      "lines": 95,
      "statements": 95
    }
  }
}

编辑2:以下测试也不影响测试覆盖率:

test('when there is no action / testing the default', () => {
  expect(addressReducer(undefined, {foo: 'bar'})).toEqual({address: ''})
})

我仍然不明白为什么最初的默认测试实现从分支覆盖的 Angular 来看不等价。

Answer 1

myReducer() 的最后一个测试涵盖了 initialState 的默认值的情况，在您的情况下是 {foo: ''} 得到应用。