test(useTitle): add unit tests

packages/core/useTitle/index.test.ts

@@ -0,0 +1,91 @@
+import { computed, ref } from 'vue-demi'
+import { useTitle } from '.'
+
+describe('useTitle', () => {
+  it('throws error when using both `observe` and `titleTemplate`', () => {
+    expect(() => {
+      useTitle(null, { observe: true, titleTemplate: '%s' })
+    }).toThrowErrorMatchingInlineSnapshot('"Cannot use `observe` and `titleTemplate` together."')
+  })
+
+  it('without param', () => {
+    const title = useTitle()
+    expect(title.value).toEqual('')
+    title.value = 'new title'
+    expect(title.value).toEqual('new title')
+  })
+
+  describe('with writable param', () => {
+    it('string', () => {
+      const title = useTitle('old title')
+      expect(title.value).toEqual('old title')
+      title.value = 'new title'
+      expect(title.value).toEqual('new title')
+    })
+
+    it('null', () => {
+      const title = useTitle(null)
+      expect(title.value).toEqual('')
+      title.value = 'new title'
+      expect(title.value).toEqual('new title')
+    })
+
+    it('undefined', () => {
+      const title = useTitle(undefined)
+      expect(title.value).toEqual('')
+      title.value = 'new title'
+      expect(title.value).toEqual('new title')
+    })
+
+    describe('ref param', () => {
+      it('string', () => {
+        const targetRef = ref('old title')
+        const title = useTitle(targetRef)
+        expect(title.value).toEqual('old title')
+        targetRef.value = 'new title'
+        expect(title.value).toEqual('new title')
+        title.value = 'latest title'
+        expect(title.value).toEqual('latest title')
+      })
+
+      it('null', () => {
+        const targetRef = ref<null | string>(null)
+        const title = useTitle(targetRef)
+        expect(title.value).toEqual(null)
+        targetRef.value = 'new title'
+        expect(title.value).toEqual('new title')
+        title.value = 'latest title'
+        expect(title.value).toEqual('latest title')
+      })
+
+      it('undefined', () => {
+        const targetRef = ref<undefined | string>(undefined)
+        const title = useTitle(targetRef)
+        expect(title.value).toEqual(undefined)
+        targetRef.value = 'new title'
+        expect(title.value).toEqual('new title')
+        title.value = 'latest title'
+        expect(title.value).toEqual('latest title')
+      })
+    })
+  })
+
+  describe('with readonly param', () => {
+    it('computed', () => {
+      const condition = ref(false)
+      const target = computed(() => condition.value ? 'new title' : 'old title')
+      const title = useTitle(target)
+      expect(title.value).toEqual('old title')
+      condition.value = true
+      expect(title.value).toEqual('new title')
+      // title.value = '' // typed error
+    })
+
+    it('function', () => {
+      const target = () => 'new title'
+      const title = useTitle(target)
+      expect(title.value).toEqual('new title')
+      // title.value = '' // typed error
+    })
+  })
+})