# XCTAssertThrowsError(_:_:file:line:_:) Asserts that an expression throws an error. ``` func XCTAssertThrowsError(_ expression: @autoclosure () throws -> T, _ message: @autoclosure () -> String = "", file: StaticString = #filePath, line: UInt = #line, _ errorHandler: (any Error) -> Void = { _ in }) ``` ## Parameters `expression` An expression that can throw an error. `message` An optional description of a failure. `file` The file where the failure occurs. The default is the filename of the test case where you call this function. `line` The line number where the failure occurs. The default is the line number where you call this function. `errorHandler` An optional handler for errors that `expression` throws. ## Discussion --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)