You’ve written (or are about to write) an API in Grails. Which is quite easy, especially with all the REST API improvements in Grails 2.3. Now you want to ensure your API works correctly when the first users start hitting it with JSON. But you don’t want to write and maintain raw JSON strings – what are some existing libraries you could use to help make testing your API easier?
Let’s walk through some quick examples of testing a Grails API with the Grails Rest Client Builder plugin, the Groovy Http Builder library, and the Apache Fluent Http Client library. We’ll use JSON in these examples, but you could easily substitute XML if your API supports that format.
Let’s start with a simple Grails API for a Person class with a first and last name. We’ll use the Grails 2.3 @Resource annotation to quickly create the API from the domain class:
If your project doesn’t already have a plugin that enables functional testing (e.g. Geb, Webdriver, etc.), then you’ll need to add code similar to this to your scripts/_Events.groovy file to enable the functional test phase. I borrowed this code from the Functional Test plugin:
If you do have a plugin that enables the functional test phase, don’t add this to your _Events.groovy file. Otherwise your functional tests may run twice.
The Grails Rest Client Builder plugin is built to call Rest APIs from your application code, but it can easily be used to call APIs in your test as well. Here is a quick example of using a GET to retrieve a person:
One thing to note when issuing a GET with the REST client builder plugin – I had to set the ‘accept’ type to JSON. Otherwise the plugin defaulted to accepting the String type and the API complained that String was an unsupported type and threw a 415 error.
And using a POST to create a new Person:
The Groovy Http Builder library provides a handy syntax to call APIs over Http. In these examples we’ll use the RESTClient subset of the Http Builder library since it is geared specifically towards calling Rest APIs and provides a more concise syntax for doing so.
First, we’ll issue a GET to fetch an existing Person:
Then we’ll POST a new Person to our API:
The Apache Http Client library is a popular, well-worn Java library that dates back over a decade, but it is still widely used. We’ll use it’s Fluent version for its powerful and readable builder-like syntax.
We’ll start with a GET to grab an existing Person:
Then use a POST to create a new Person:
I hope these examples will give you a starting place to see what options are available to test your Grails API. And check out the full source code for this testing project on GitHub: https://github.com/craigatk/grails-api-testing