test: test for v3 useCssModule (#750)

Co-authored-by: webfansplz <>

Author: webfansplz

test/v3/runtime-core/useCssModule.spec.ts

@@ -0,0 +1,46 @@
+import { useCssModule, createApp } from '../../../src'
+import { mockWarn } from '../../helpers'
+import { proxy } from '../../../src/utils'
+
+function injectStyles(this: any, style: object) {
+  proxy(this, '$style', {
+    get: function () {
+      return style
+    },
+  })
+}
+
+describe('api: useCssModule', () => {
+  mockWarn(true)
+
+  function mountWithModule(modules: object) {
+    let res
+    const Comp = {
+      beforeCreate() {
+        injectStyles.call(this, modules)
+      },
+      setup() {
+        res = useCssModule()
+      },
+    }
+    const root = document.createElement('div')
+    createApp(Comp).mount(root)
+    return res
+  }
+
+  it('basic usage', () => {
+    const modules = {
+      $style: {
+        red: 'red',
+      },
+    }
+    expect(mountWithModule(modules.$style)).toMatchObject(modules.$style)
+  })
+
+  it('warn out of setup usage', () => {
+    useCssModule()
+    expect(
+      '[Vue warn]: useCssModule must be called inside setup()'
+    ).toHaveBeenWarned()
+  })
+})