iOS UITesting opening external link

I am writing UITests for opening up an external link in iOS app. What is the possible XCTAssertTrue or XCTAssertFalse thatcan work test case when external link is opened.

Currently i am checking if the clicked button is visible or not but its not working.

 XCTAssertFalse(btn.isVisible(), "Component should not be visible", file:  file, line: line)