# require(throws:_:sourceLocation:performing:) Check that an expression always throws an error of a given type, and throw an error if it does not. ``` @discardableResult @freestanding(expression) macro require(throws errorType: E.Type, _ comment: @autoclosure () -> Comment? = nil, sourceLocation: SourceLocation = #_sourceLocation, performing expression: () async throws -> R) -> E where E : Error ``` ## Parameters `errorType` The type of error that is expected to be thrown. If `expression` could throw *any* error, or the specific type of thrown error is unimportant, pass `(any Error).self`. `comment` A comment describing the expectation. `sourceLocation` The source location to which recorded expectations and issues should be attributed. `expression` The expression to be evaluated. ## Return Value The instance of `errorType` that was thrown by `expression`. ## Overview> Throws: An instance of ``doc://org.swift.testing/documentation/Testing/ExpectationFailedError`` if `expression` does not > throw a matching error. The error thrown by `expression` is not rethrown. Use this overload of `#require()` when the expression `expression` *should* throw an error of a given type: ```swift try #require(throws: EngineFailureError.self) { FoodTruck.shared.engine.batteryLevel = 0 try FoodTruck.shared.engine.start() } ``` If `expression` does not throw an error, or if it throws an error that is not an instance of `errorType`, an [`Issue`](/documentation/Testing/Issue) is recorded for the test that is running in the current task and an instance of [`ExpectationFailedError`](/documentation/Testing/ExpectationFailedError) is thrown. Any value returned by `expression` is discarded. > Note: If you use this macro with a Swift compiler version lower than 6.1, > it doesn’t return a value. If the thrown error need only equal another instance of [`Error`](https://developer.apple.com/documentation/swift/error), use [`require(throws:_:sourceLocation:performing:)`](/documentation/Testing/require(throws:_:sourceLocation:performing:)-4djuw) instead. If `expression` should *never* throw, simply invoke the code without using this macro. The test will then fail if an error is thrown. --- 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)