Настройка и написание юнит-тестов с Jest

npm install --save-dev jest @vue/test-utils vue-jest babel-jest

module.exports = {
  preset: '@vue/cli-plugin-unit-jest',
  transform: {
    '^.+\\.vue$': 'vue-jest',
  },
};

// src/components/Message.vue
<template>
  <div>{{ message }}</div>
</template>

<script>
export default {
  props: ['message'],
};
</script>

import { shallowMount } from '@vue/test-utils';
import Message from '@/components/Message.vue';

describe('Message.vue', () => {
  it('renders props.message when passed', () => {
    const message = 'Hello Jest!';
    const wrapper = shallowMount(Message, {
      propsData: { message },
    });
    expect(wrapper.text()).toMatch(message);
  });
});

// src/components/Button.vue
<template>
  <button @click="handleClick">Click me</button>
</template>

<script>
export default {
  methods: {
    handleClick() {
      this.$emit('clicked');
    },
  },
};
</script>

import { shallowMount } from '@vue/test-utils';
import Button from '@/components/Button.vue';

describe('Button.vue', () => {
  it('calls handleClick when button is clicked', () => {
    const handleClick = jest.fn();
    const wrapper = shallowMount(Button);
    wrapper.setMethods({ handleClick });
    wrapper.find('button').trigger('click');
    expect(handleClick).toHaveBeenCalled();
  });

  it('emits "clicked" event when button is clicked', () => {
    const wrapper = shallowMount(Button);
    wrapper.find('button').trigger('click');
    expect(wrapper.emitted('clicked')).toBeTruthy();
  });
});

// src/store/modules/counter.js
export default {
  state: {
    count: 0,
  },
  mutations: {
    increment(state) {
      state.count++;
    },
  },
  actions: {
    increment({ commit }) {
      commit('increment');
    },
  },
};

import counterModule from '@/store/modules/counter';

describe('counter.js', () => {
  it('increments count in state', () => {
    const state = {
      count: 0,
    };
    counterModule.mutations.increment(state);
    expect(state.count).toBe(1);
  });

  it('commits increment mutation', () => {
    const commit = jest.fn();
    counterModule.actions.increment({ commit });
    expect(commit).toHaveBeenCalledWith('increment');
  });
});