---
title: "addTestObserver(_:)"
framework: xctest
role: symbol
role_heading: Instance Method
path: "xctest/xctestobservationcenter/addtestobserver(_:)"
---

# addTestObserver(_:)

Registers an object conforming to XCTestObservation as an observer for the current test session.

## Declaration

```swift
func addTestObserver(_ testObserver: any XCTestObservation)
```

## Discussion

Discussion Observers may be added at any time, but will not receive events that occurred before they were registered. The observation center maintains a strong reference to observers.Events may be delivered to observers in any order. Given observers A and B, A may be notified of a test failure before or after B. Any ordering dependencies or serialization requirements must be managed by clients.

## See Also

### Managing Observers

- [removeTestObserver(_:)](xctest/xctestobservationcenter/removetestobserver(_:).md)