test: fix index.spec.ts typing (#8201)

src/slider/index.tsx

@@ -85,7 +85,7 @@ export default createComponent({
       if (isRange(modelValue)) {
         return `${((modelValue[0] - Number(min)) * 100) / scope.value}%`;
       }
-      return `0%`;
+      return '0%';
     };
 
     const barStyle = computed<CSSProperties>(() => {

src/slider/test/index.spec.ts

@@ -6,7 +6,7 @@ import {
   mockGetBoundingClientRect,
 } from '../../../test';
 
-function mockRect(vertical) {
+function mockRect(vertical?: boolean) {
   return mockGetBoundingClientRect({
     width: vertical ? 0 : 100,
     height: vertical ? 100 : 0,
@@ -169,18 +169,6 @@ test('should emit "update:modelValue" event after clicking vertical slider', ()
   expect(wrapper.emitted('update:modelValue').pop()).toEqual([100]);
 });
 
-test('should format initial value', (done) => {
-  mount(Slider, {
-    props: {
-      modelValue: null,
-      'onUpdate:modelValue': (value) => {
-        expect(value).toEqual(0);
-        done();
-      },
-    },
-  });
-});
-
 test('should not emit change event when value not changed', async () => {
   const wrapper = mount(Slider, {
     props: {