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## `expectEmitAnonymous`

### Signature

```solidity
function expectEmitAnonymous() external;
function expectEmitAnonymous(address emitter) external;
function expectEmitAnonymous(bool checkTopic0, bool checkTopic1, bool checkTopic2, bool checkTopic3, bool checkData) external;
function expectEmitAnonymous(bool checkTopic0, bool checkTopic1, bool checkTopic2, bool checkTopic3, bool checkData, address emitter) external;
```

### Description

Asserts that a specific anonymous event is emitted during the next call. This is the [`expectEmit`](/reference/cheatcodes/expect-emit) counterpart for events declared with the `anonymous` keyword.

**Steps to use:**

1. Call `expectEmitAnonymous`, optionally specifying which topics to check
2. Emit the expected anonymous event in your test
3. Perform the call that should emit the event

Because anonymous events do not reserve topic 0 for the event signature, all four topics carry indexed parameters and each of them can be checked individually, starting with `checkTopic0`. The overloads without booleans enable all topic and data checks.

### Parameters

| Parameter     | Type      | Description                                    |
|---------------|-----------|------------------------------------------------|
| `checkTopic0` | `bool`    | Whether to check the first indexed parameter   |
| `checkTopic1` | `bool`    | Whether to check the second indexed parameter  |
| `checkTopic2` | `bool`    | Whether to check the third indexed parameter   |
| `checkTopic3` | `bool`    | Whether to check the fourth indexed parameter  |
| `checkData`   | `bool`    | Whether to check the non-indexed event data    |
| `emitter`     | `address` | The expected address that emits the event      |

### Examples

```solidity [test/ExpectEmitAnonymous.t.sol]
contract Emitter {
    event Message(address indexed sender, uint256 indexed id, uint256 amount) anonymous;

    function send(uint256 id, uint256 amount) external {
        emit Message(msg.sender, id, amount);
    }
}

contract ExpectEmitAnonymousTest is Test {
    event Message(address indexed sender, uint256 indexed id, uint256 amount) anonymous;

    Emitter emitter = new Emitter();

    function testEmitsAnonymousMessage() public {
        vm.expectEmitAnonymous(address(emitter));
        emit Message(address(this), 1, 10 ether);

        emitter.send(1, 10 ether);
    }
}
```

### Gotchas

:::note
Unlike regular events, anonymous events have no signature topic, so nothing identifies the event type on-chain. With all checks disabled, any anonymous log emitted by the next call matches.
:::

### Related Cheatcodes

* [`expectEmit`](/reference/cheatcodes/expect-emit) - Assert non-anonymous events, including sequence-matching rules that also apply here
* [`recordLogs`](/reference/cheatcodes/record-logs) - Record all emitted events