unexpected/documentation/assertions/function/to-have-arity.md

Extensible BDD assertion toolkit

Asserts that the function takes the given number of arguments.

```javascript
expect(Math.max, 'to have arity', 2);
expect('wat'.substring, 'to have arity', 2);
```

In case of a failing expectation you get the following output:

```javascript
expect(function wat(foo, bar) {
  return foo + bar;
}, 'to have arity', 3);
```

```output
expected function wat(foo, bar) { return foo + bar; } to have arity 3
```