test(core): unit validating clockskew offset is updated when client c…

…lock back and forth (#12495)

packages/core/__tests__/clients/middleware/signing/utils/getUpdatedSystemClockOffset.test.ts

@@ -15,15 +15,15 @@ describe('getUpdatedSystemClockOffset', () => {
 		Date.now = jest.fn(() => signingDate.valueOf());
 	});
 
-	test('returns the current offset if not skewed', () => {
+	it('should return the current offset if not skewed', () => {
 		mockIsClockSkewed.mockReturnValue(false);
 		const offset = 1500;
 		expect(getUpdatedSystemClockOffset(signingDate.getTime(), offset)).toBe(
 			offset
 		);
 	});
 
-	test('returns the updated offset if system clock is behind', () => {
+	it('should return the updated offset if system clock is behind', () => {
 		mockIsClockSkewed.mockReturnValue(true);
 		const clockTime = new Date(signingDate);
 		clockTime.setMinutes(signingDate.getMinutes() + 15);
@@ -32,12 +32,25 @@ describe('getUpdatedSystemClockOffset', () => {
 		);
 	});
 
-	test('returns the updated offset if system clock is ahead', () => {
+	it('should return the updated offset if system clock is ahead', () => {
 		mockIsClockSkewed.mockReturnValue(true);
 		const clockTime = new Date(signingDate);
 		clockTime.setMinutes(signingDate.getMinutes() - 15);
 		expect(getUpdatedSystemClockOffset(clockTime.getTime(), 0)).toBe(
 			-15 * 60 * 1000
 		);
 	});
+
+	// Addresses: https://github.com/aws-amplify/amplify-js/issues/12450#issuecomment-1787945008
+	it('should return the updated offset if system clock is back and forth', () => {
+		// initialize client clock skew to be 15 mins behind
+		mockIsClockSkewed.mockReturnValue(true);
+		const clockTime = new Date(signingDate);
+		clockTime.setMinutes(signingDate.getMinutes() - 15);
+		let offset = getUpdatedSystemClockOffset(clockTime.getTime(), 0);
+		// client clock skew is now 15 mins ahead, making is sync with server clock
+		clockTime.setMinutes(signingDate.getMinutes() + 15);
+		offset = getUpdatedSystemClockOffset(clockTime.getTime(), offset);
+		expect(offset).toBe(0);
+	});
 });