test(query-core): add test case for keepPreviousData (#8719)

Author: manudeli

packages/query-core/src/__tests__/utils.test.tsx

@@ -4,6 +4,7 @@ import {
   addToStart,
   isPlainArray,
   isPlainObject,
+  keepPreviousData,
   matchMutation,
   partialMatchKey,
   replaceEqualDeep,
@@ -405,6 +406,13 @@ describe('core/utils', () => {
     })
   })
 
+  describe('keepPreviousData', () => {
+    it('should return the parameter as is', () => {
+      const x = { a: 1, b: 2 }
+      expect(keepPreviousData(x)).toEqual(x)
+    })
+  })
+
   describe('addToEnd', () => {
     it('should add item to the end of the array', () => {
       const items = [1, 2, 3]