feat(components): [cascader] add unit test cases

packages/components/cascader/__tests__/cascader.test.tsx

@@ -624,4 +624,40 @@ describe('Cascader.vue', () => {
       expect(prefixSlotEl?.textContent).toBe('-=-prefix-=-')
     })
   })
+  describe('Cascader - showFirstLevelOnly', () => {
+    it('should only display first level label after clicking sub-option', async () => {
+      const wrapper = mount(() => <Cascader options={OPTIONS} topLevelOnly />)
+      const trigger = wrapper.find(TRIGGER)
+
+      await trigger.trigger('click')
+      ;(document.querySelector(NODE) as HTMLElement).click()
+      await nextTick()
+      ;(document.querySelectorAll(NODE)[1] as HTMLElement).click()
+      await nextTick()
+      expect(wrapper.find('input').element.value).toBe('Zhejiang')
+    })
+    it('should only display first level labels for multiple selected sub-options', async () => {
+      const wrapper = mount(() => (
+        <Cascader options={OPTIONS} topLevelOnly multiple />
+      ))
+      const trigger = wrapper.find(TRIGGER)
+      await trigger.trigger('click')
+      await nextTick()
+      const firstNode = document.querySelector(NODE) as HTMLElement
+      expect(firstNode).not.toBeNull()
+      firstNode.click()
+      await nextTick()
+      const secondNode = document.querySelectorAll(NODE)[1] as HTMLElement
+      expect(secondNode).not.toBeNull()
+      secondNode.click()
+      await nextTick()
+      const thirdNode = document.querySelectorAll(NODE)[2] as HTMLElement
+      expect(thirdNode).not.toBeNull()
+      thirdNode.click()
+      await nextTick()
+      const inputValue = (wrapper.find('input').element as HTMLInputElement)
+        .value
+      expect(inputValue).toBe('Zhejiang')
+    })
+  })
 })