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<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Overriding dependencies in a test with playframework and guice</title> <meta name="viewport" content="width=device-width"> <link href="/assets/css/style.css" rel="stylesheet" />  <link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png"> <link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png"> <link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png"> <link rel="manifest" href="/site.webmanifest">  </head> <body> <div id="header-outer"> <header id="header"> <h1><a href="/">Michael Pollmeier ~ dev blog</a></h1> <nav> <ul> <li><a href="/">blog posts</a></li> <li><a href="/presentations">presentations</a></li> <li><a href="http://twitter.com/pollmeier">twitter</a></li> <li><a href="/feed.xml">rss</a></li> <li><a href="/about">about me</a></li> </ul> </nav> </header> </div> <div id="page"> <div id="content"> <article class="post"> <h1><a href="/2015/09/25/playframework-guice-di">Overriding dependencies in a test with playframework and guice</a></h1> Posted on Sep 25, 2015 tags:  scala,  recipe,  test,  playframework <div class="post-content"><a href="https://www.playframework.com/">Playframework</a> recently made <a href="https://github.com/google/guice">guice</a> its’ default dependency injection (DI) framework. So I was looking for a simple example where a controller defines a dependency which then get’s overridden for a FakeApplication in a test. I expected a simple gist in the docs for this very common (I thought) use case, but didn’t find one. Here is what I ended up with, which is based on <a href="http://www.scalatest.org/plus/play">ScalaTest + Play</a>. The nice thing about this setup is that it always tests the whole app, incl. the routing. Often developers only test a specific controller method, which leaves some space for bugs. app/controller/PersonController.scala: <div class="language-scala highlighter-rouge"><div class="highlight"><pre class="highlight"><code>class Hello { def sayHello(name: String) = "Hello " + name } class PersonController @Inject() (hello: Hello) extends Controller { def index = Action { Ok(hello.sayHello("michael")) } } </code></pre></div></div> test/ApplicationTest.scala: <div class="language-scala highlighter-rouge"><div class="highlight"><pre class="highlight"><code>import controllers._ import org.scalatest._ import org.scalatestplus.play._ import play.api.inject.bind import play.api.inject.guice.GuiceInjector import play.api.inject.guice.GuiceableModule import play.api.test._ import play.api.test.Helpers._ abstract class MyPlaySpec extends WordSpec with Matchers with OptionValues with WsScalaTestClient class GermanHello extends Hello { override def sayHello(name: String) = "Hallo " + name } class ApplicationTest extends MyPlaySpec with OneAppPerTestWithOverrides { override def overrideModules = Seq( bind[Hello].to[GermanHello] ) "render the index page" in { val home = route(FakeRequest(GET, "/")).get status(home) shouldBe OK contentAsString(home) shouldBe "Hallo michael" } } </code></pre></div></div> test/OneAppPerTestWithOverrides.scala: <div class="language-scala highlighter-rouge"><div class="highlight"><pre class="highlight"><code>package org.scalatestplus.play import play.api.Application import play.api.inject.guice.GuiceApplicationBuilder import play.api.inject.bind import play.api.inject.guice.GuiceableModule import play.api.test._ import org.scalatest._ trait OneAppPerTestWithOverrides extends SuiteMixin { this: Suite ⇒ def overrideModules: Seq[GuiceableModule] = Nil def newAppForTest(testData: TestData): Application = new GuiceApplicationBuilder() .overrides(overrideModules: _*) .build private var appPerTest: Application = _ implicit final def app: Application = synchronized { appPerTest } abstract override def withFixture(test: NoArgTest) = { synchronized { appPerTest = newAppForTest(test) } Helpers.running(app) { super.withFixture(test) } } } </code></pre></div></div> A full application (and test) is <a href="https://github.com/mpollmeier/play-scala-di">here</a>, and the discussion on the mailinglist <a href="https://groups.google.com/forum/#!topic/play-framework/gW8FXC3K30E">here</a>. More details on guice DI in playframework are in the <a href="https://www.playframework.com/documentation/2.4.x/ScalaTestingWithGuice">documentation</a> PS: another handy tipp: if you want to get the used binding for a given class, you can just ask the guice injector inside a test: <div class="language-scala highlighter-rouge"><div class="highlight"><pre class="highlight"><code>val hello = app.injector.instanceOf(classOf[Hello]) </code></pre></div></div> </div> <hr /> <div class="footer"> If you liked this post you may want to follow me on <a href="http://twitter.com/pollmeier">Twitter</a> and subscribe to the <a href="/feed.xml">RSS feed</a>. </div> </article> </div> </div> <script src="/assets/js/jquery.min.js"></script> <script src="/assets/js/jquery.mobilemenu.min.js"></script> <script> $(document).ready(function(){ $('#sidebar nav ul').mobileMenu({'topOptionText': 'Menu', 'prependTo': '#sidebar nav'}); }); </script> </body> </html>