Vue.js/test/unit/features/options/mixins.spec.js

import Vue from 'vue'
const mergeOptions = Vue.util.mergeOptions

describe('Options mixins', () => {
  it('vm should have options from mixin', () => {
    const mixin = {
      directives: {
        c: {}
      },
      methods: {
        a: function () {}
      }
    }

    const vm = new Vue({
      mixins: [mixin],
      methods: {
        b: function () {}
      }
    }).$mount()

    expect(vm.a).toBeDefined()
    expect(vm.b).toBeDefined()
    expect(vm.$options.directives.c).toBeDefined()
  })

  it('should call hooks from mixins first', () => {
    const a = {}
    const b = {}
    const c = {}
    const f1 = function () {}
    const f2 = function () {}
    const f3 = function () {}
    const mixinA = {
      a: 1,
      template: 'foo',
      directives: {
        a: a
      },
      created: f1
    }
    const mixinB = {
      b: 1,
      directives: {
        b: b
      },
      created: f2
    }
    const result = mergeOptions({}, {
      directives: {
        c: c
      },
      template: 'bar',
      mixins: [mixinA, mixinB],
      created: f3
    })
    expect(result.a).toBe(1)
    expect(result.b).toBe(1)
    expect(result.directives.a).toBe(a)
    expect(result.directives.b).toBe(b)
    expect(result.directives.c).toBe(c)
    expect(result.created[0]).toBe(f1)
    expect(result.created[1]).toBe(f2)
    expect(result.created[2]).toBe(f3)
    expect(result.template).toBe('bar')
  })

  it('mixin methods should not override defined method', () => {
    const f1 = function () {}
    const f2 = function () {}
    const f3 = function () {}
    const mixinA = {
      methods: {
        xyz: f1
      }
    }
    const mixinB = {
      methods: {
        xyz: f2
      }
    }
    const result = mergeOptions({}, {
      mixins: [mixinA, mixinB],
      methods: {
        xyz: f3
      }
    })
    expect(result.methods.xyz).toBe(f3)
  })

  it('should accept constructors as mixins', () => {
    const mixin = Vue.extend({
      directives: {
        c: {}
      },
      methods: {
        a: function () {}
      }
    })

    const vm = new Vue({
      mixins: [mixin],
      methods: {
        b: function () {}
      }
    }).$mount()

    expect(vm.a).toBeDefined()
    expect(vm.b).toBeDefined()
    expect(vm.$options.directives.c).toBeDefined()
  })
})