How to Set HTTP Error Responses in MUnit Testing

The development of efficient and robust MuleSoft applications requires comprehensive unit testing, and MUnit is an invaluable tool for this purpose. In this blog post, we'll delve into some tips for handling error status returned from the 'HTTP Request' backend during unit testing.

When we have logic that branches based on the contents of the response, the unit testing approach becomes a bit more intricate. The response body of the error status returned from the backend is stored in 'error.errorMessage.payload'. In typical situations, you might want to directly assign a value to this field using 'Mock when'. However, 'Mock when' doesn't allow you to set a value to 'error.errorMessage.payload'.

So, how do we work around this limitation? Here comes the 'Then Call' to the rescue. In the subflow called by 'Then Call', you can use the 'Set Event' to establish an exception. This way, you're able to mimic the desired behavior by setting the 'error.errorMessage.payload' as part of the flow.

The type of exception you're looking to set here should be an instance of the 'ResponseValidatorTypedException' class from Java. It accurately represents the sort of exception that would occur in a live environment when an error status is returned from the backend.

%dw 2.0
output application/java

var detailMessage = 'Internal server error'
var errorType = java!org::mule::extension::http::api::error::HttpError::INTERNAL_SERVER_ERROR
---
java!org::mule::extension::http::api::request::validator::ResponseValidatorTypedException::new(detailMessage, errorType, message)

By leveraging this technique, you can achieve a more accurate and efficient unit testing process for your MuleSoft applications. It allows you to replicate the behavior of the 'HTTP Request' backend error status more accurately in your tests, ensuring that your code is capable of handling such scenarios in real-world operations.

Remember, comprehensive unit testing is a crucial aspect of creating reliable and robust MuleSoft applications. Therefore, understanding how to handle and mimic different error statuses during testing can significantly enhance your application's quality and reliability.

In conclusion, unit testing with MUnit in MuleSoft Applications might appear challenging, but with the right approach and understanding, it can be manageable and effective. Hopefully, this post has offered you some useful insights into this topic. Happy testing!