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# XCTAssertNil

Asserts that an expression is `nil`.

```
#define XCTAssertNil(expression, ...)
```

## Parameters

`expression`

An expression of `id` type.

`…`

An optional description of the failure. A literal <doc://com.apple.documentation/documentation/Foundation/NSString>, optionally with string format specifiers.

## Discussion

This function generates a failure when `expression != nil`.

---

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