Add clearCache test

AWSAppSyncTests/AWSAppSyncTests.swift

@@ -110,6 +110,55 @@ class AWSAppSyncTests: XCTestCase {
         wait(for: [successfullistEventExpectation], timeout: 5.0)
     }
 
+    func testClearCache() {
+        shouldDeleteDuringTearDown = true
+        let mutationExpectation = expectation(description: "Mutation done successfully.")
+
+        let addEvent = AddEventMutation(
+            name: EventName,
+            when: EventTime,
+            where: EventLocation,
+            description: EventDescription)
+
+        appSyncClient.perform(mutation: addEvent) { (result, error) in
+            defer { mutationExpectation.fulfill() }
+
+            XCTAssertNil(error, "Error expected to be nil, but is not.")
+            XCTAssertNotNil(result?.data?.createEvent?.id, "Expected service to return a UUID.")
+            XCTAssertEqual(self.EventName, result?.data?.createEvent?.name, "Event names should match.")
+        }
+
+        wait(for: [mutationExpectation], timeout: 5.0)
+
+        let query = ListEventsQuery()
+
+        let fetchQueryIgnoringCacheExpectation = expectation(description: "Fetch query ignoring cache")
+        let emptyCacheExpectation = expectation(description: "Fetch query from empty cache")
+
+        appSyncClient.fetch(query: query, cachePolicy: .fetchIgnoringCacheData) { (result, error) in
+            defer { fetchQueryIgnoringCacheExpectation.fulfill() }
+
+            XCTAssertNil(error, "Error expected to be nil, but is not.")
+            XCTAssertNotNil(result?.data?.listEvents?.items, "Items array should not be empty.")
+            XCTAssertGreaterThan(result?.data?.listEvents?.items?.count ?? 0, 0, "Expected service to return at least 1 event.")
+
+            do {
+                try self.appSyncClient.store?.clearCache().await()
+            } catch {
+                XCTFail()
+            }
+
+            self.appSyncClient.fetch(query: query, cachePolicy: .returnCacheDataDontFetch) { (result, error) in
+                defer { emptyCacheExpectation.fulfill() }
+
+                XCTAssertNil(result, "Expected empty cache")
+                XCTAssertNil(error, "Expected no error")
+            }
+        }
+
+        wait(for: [fetchQueryIgnoringCacheExpectation, emptyCacheExpectation], timeout: 5.0)
+    }
+
     func testMutation() {
         shouldDeleteDuringTearDown = true
         let successfulMutationEventExpectation = expectation(description: "Mutation done successfully.")