---
title: Chaijs Assertexpression Message
localeTitle: Chaijs Assertexpression Message
---
[@param](/users/param) {Mixed} expressionto test for truthiness

*   [@param](/users/param) {String} messageto exibir no erro

Escreva suas próprias expressões de teste.
```
assert('foo' !== 'bar', 'foo is not bar'); 
 assert(Array.isArray(<a href='http://chaijs.com/api/assert/' target='_blank' rel='nofollow'>]), 'empty arrays are arrays'); 
```

detalhes: \[http://chaijs.com/api/assert/