# XCTKeyPathExpectation.Predicate A function the key path expectation uses to test the value of an observed property. ``` typealias Predicate = @Sendable (T, NSKeyValueObservedChange) async -> Bool ``` ## Parameters `observedObject` The observed object to evaluate with the property that changes. `change` A value that describes the observed change. ## Return Value Returns if the change fulfills the expectation; otherwise, . ## Discussion A key path expectation uses this function to determine whether the value of the observed property fulfills the conditions of the expectation. The system invokes the function asyncronously on a detached task and may call the function more that once. --- 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)