How and where to test if the JSON request objects generated by the front-end is valid?

Question

We have built a complex Angular application that sends multiple HTTP request to a REST service that is also built in house. Since both the frontend and the backend is being developed in parallel, bugs can happen in either side. It could be a bug in the REST service, or it can be a problem with the HTTP Request generated from the front-end. When a bug has been reported, it's important to identify where the error occurs. There are specific structures for each of the requests. The data models are mostly populated when the users give inputs in a form or a directiveHow do we approach testing these HTTP requests? * Can we only rely on unit tests? * Can the testing be done with dummy data that produces a pre-defined JSON object? * Or should integration tests be done with the actual data?And by which ever method we pick, how do we identify where the error lies when there is a bug?

Answer 1

This is a pretty good question. There are a few things I'd consider moving forward. For one, are you authoring this in TypeScript? Is your JSON data structured? By this I mean, could you use a JSON schema and AJV validator on both the front-end (to ensure that what is being sent is at least valid to the schema), and then be able to evaluate on the server side (the api route) that what has been sent is still valid using, again, a schema validator like AJV? Any sensitive checks such as looking up user data or sensitive app data should be handled on the service/api layer. It's faster, and, you don't want to expose those kinds of lookups to the client (front-end).

If you're developing this application in parallel you should be ensuring that the data your sending follows a standard (schema) that both teams have agreed on. You should standardize on a validation tool, like AJV or something else, to ensure that what is sent matches the schema, and what is received matches the schema.

The only thing Unit tests are going to do in this case is just have some dummy data that's in the correct format (e.g., the schema you agreed on). But unit tests aren't going to cover some of the patterns that I mentioned above... both teams need to have solid development practices.