How to Unit Test when using ScalaJ-Http? - scala

Question

I am looking to use ScalaJ-Http as a http client. Link: https://github.com/scalaj/scalaj-http
How would I mock Http or HttpRequest in a unit test for a class with a line of code like this val response: HttpResponse[String] = Http("http://foo.com/search").param("q","monkeys").asString?
The class will take the url and params from method call arguments. So I cannot inject HttpRequest.

Answer 1

What I did was create a ScalajHttp wrapper class like so:
import scalaj.http.{Http, HttpRequest}
/**
* This wraps the Scalaj Http object so it can be injected.
*/
class ScalajHttp {
def url(url: String): HttpRequest = Http(url)
}
Then you can easily inject it into another class:
class Foo(http: ScalajHttp) {
def doBar() = {
val response = http.url("http://...").asString
}
}
Then for mocking you can use something like Specs2 and create mock of ScalajHttp.

Answer 2

Curious if you already had a solution for this. I came across your post with the same question.
I finally solved it for now by just creating a 'dummy-service' in the test itself using Scalatra/Jetty and specifying the expected responses in there. So, it's not really mocking, but it'll do for me.
Downside to this approach is that you have to include Scalatra, Jetty-server and Jetty-servlet as extra dependencies (optionally with scope=test).
def mockService: Server = {
class MockedServlet extends ScalatraServlet {
get("/") {
// fill in whatever you expect here
Ok("I'm alive!")
}
}
class ServletMounter extends LifeCycle {
override def init(context: ServletContext): Unit = {
context.mount(new MockedServlet, "/mock")
}
}
new Server(20002) {
val servlet = new ServletContextHandler(ServletContextHandler.NO_SESSIONS) {
addEventListener(new ScalatraListener() {
override def probeForCycleClass(classLoader: ClassLoader): (String, LifeCycle) = {
(classOf[ServletMounter].getSimpleName, new ServletMounter)
}
})
}
setHandler(servlet)
}
}
private val server = mockService
override protected def beforeAll(): Unit = {
super.beforeAll()
server.start()
}
override protected def afterAll(): Unit = {
server.stop()
server.destroy()
super.afterAll()
}
// a simple test
"service up" should "return a 200 when the mocked service is up" in {
val response = Http("http://localhost:20002/mock/").asString
response.code shouldBe 200
response.body shouldBe "I'm alive!"
}
Edit March 2nd, 2017:
After some more consideration I changed my code such that I have the HTTP call via scalaj-http in a 'facade' trait, that I am able to mock in my tests. Now, rather than doing the actual HTTP request, I mock the facade and send back the expected HTTPResponse. In comparison with the solution shown above, this is much cleaner, the dependencies mentioned above aren't necessary anymore and the setup is easier. The facade can be 'injected' into the class that does the HTTP call as either a constructor parameter or as a self-type annotation.