callCount is undefined when testing with sinon

[lefta]

Reproduction

See below

Steps to reproduce the bug

package.json

{
  "name": "pinia-sinon-bug-repro",
  "scripts": {
    "reproduce": "mocha ./test.js"
  },
  "dependencies": {
    "@pinia/testing": "^0.0.12",
    "@vue/test-utils": "^2.0.2",
    "chai": "^4.3.6",
    "global-jsdom": "^8.5.0",
    "mocha": "^10.0.0",
    "pinia": "^2.0.16",
    "sinon": "^14.0.0",
    "vue": "^3.2.36"
  }
}

test.js

require('global-jsdom/register')

const { defineComponent, onMounted } = require('vue')
const { defineStore } = require('pinia')
const { mount } = require('@vue/test-utils')
const { createTestingPinia } = require('@pinia/testing')
const { expect } = require('chai')
const { spy } = require('sinon')

const useStore = defineStore('appStore', {
  state: () => ({ ready: false }),
  actions: {
    async initialize() {
      this.ready = true
    },
  },
})

const Application = defineComponent({
  template: 'Hello, world !',
  setup: () => {
    const store = useStore()
    onMounted(() => store.initialize())
  }
})

describe('actions spied by sinon', () => {
  it('should have callCount property', () => {
    const pinia = createTestingPinia({ createSpy: spy })
    mount(Application, { global: { plugins: [pinia] } })
    const app = useStore()
    expect(app.initialize.callCount).to.equal(1)
  })
})

Run

npm i
npm run reproduce

Expected behavior

The test passes

Actual behavior

The test fails with

AssertionError: expected undefined to equal 1

Additional information

When a store defines an initial state, the stubbed actions lose their callCount property. When the store have no initial state, or when it is called directly (not as part of a component), everything works as expected. The following changes both make the test pass :

Line 11

// state: () => ({ ready: false }),

Lines 29 => 32

    const pinia = createTestingPinia({ createSpy: spy })
    const app = useStore()
    app.initialize()
    expect(app.initialize.callCount).to.equal(1)

[lefta]

I finally managed to get spies working by calling the store once before mounting the component. Both the following snippets are working :

    const pinia = createTestingPinia({ createSpy: spy })
    const app = useStore()
    mount(Application, { global: { plugins: [pinia] } })
    expect(app.initialize.callCount).to.equal(1)

    const pinia = createTestingPinia({ createSpy: spy })
    useStore()
    mount(Application, { global: { plugins: [pinia] } })
    const app = useStore()
    expect(app.initialize.callCount).to.equal(1)

It looks like the store needs to be registered before mounting the component. However I could not find anything about this behavior in the docs (sorry if I'm blind). Is it still a bug ?