Scala developers-Testing your Application

Using ScalaTest + Play

To use ScalaTest + Play, you'll need to add it to your build by changing the build.sbt like this:

libraryDependencies ++= Seq(
  "org.scalatestplus.play" %% "scalatestplus-play" % "x.x.x" % "test"
)

Where x.x.x is a specific version of scalatestplus-play artifact, for example 3.0.0. See the available releases here.

ScalaTest does not have to be added directly to your build. As a transitive dependency of ScalaTest + Play, the appropriate version of ScalaTest will be automatically imported. However, you must choose a ScalaTest + Play version that is compatible with your Play version. You can accomplish this by looking at the ScalaTest + Play release compatibility matrix.

In ScalaTest + Play, you define test classes by extending the PlaySpec trait. Here’s an example:

import org.scalatestplus.play._

import scala.collection.mutable

class StackSpec extends PlaySpec {

  "A Stack" must {
    "pop values in last-in-first-out order" in {
      Val stack = new mutable.Stack[Int]
      stack.push(1)
      stack.push(2)
      stack.pop() mustBe 2
      stack.pop() mustBe 1
    }
    "throw NoSuchElementException if an empty stack is popped" in {
      val emptyStack = new mutable.Stack[Int]
      a[NoSuchElementException] must be thrownBy {
        emptyStack.pop()
      }
    }
  }
}

Instead of using PlaySpec, you might specify your basic classes.

Play by itself, IntelliJ IDEA (with the Scala plugin), or Eclipse are all options for test execution (using the Scala IDE and the ScalaTest Eclipse plugin). For further information, please visit the IDE page.

Matchers in Scala developers-Testing your Application

You can build assertions using ScalaTest's matchers DSL because PlaySpec incorporates ScalaTest's MustMatchers:

import play.API.test.Helpers._
"Hello world" must endWith ("world")

Mockito in Scala developers-Testing your Application

To protect unit tests from external dependencies, use mocks. You can provide relevant data to your class without creating a DataService object, for instance, if your class depends on DataService class

 which is external.

Through the MockitoSugar trait, ScalaTest offers Mockito integration.

Use the Mockito library to mock dependencies. After mixing MockitoSugar into your test class, use Mockito:

case class Data(retrieval date: java.util.Date)

trait DataService {
  def findData: Data
}

import org.scalatest._
import org.scalatest.mock.MockitoSugar
import org.scalatestplus.play._
import org. mockito.Mockito._

class ExampleMockitoSpec extends PlaySpec with MockitoSugar {

  "MyService#isDailyData" should {
    "return true if the data is from today" in {
      Val mock data service = mock[DataService]
      when(mockDataService.findData).thenReturn(Data(new java.util.Date()))

      val myService = new MyService() {
        override def dataService = mockDataService
      }

      Val actual = myService.isDailyData
      actual mustBe true
    }
  }
}

Testing classes' public methods make good use of mocking. Mocking objects and private methods is possible, but it is much more difficult.

Unit Testing Models in Scala developers-Testing your Application

Models are not required to use a specific database data access layer to use Play. However, the Model typically has an internal reference to database access if the Application uses Anorm or Slick.

import anorm._
import anorm.SqlParser._

case class User(id: String, name: String, email: String) {
   def roles = DB.withConnection { implicit connection =>
      ...
    }
}

This can make it difficult to fake out the roles method for unit testing.

The models are typically kept separate from the database and as much logic as feasible, and database access is abstracted behind a repository layer.

Frequently Asked Questions

Why is Scala necessary?

Functional programming and Object- oriented are combined in one succinct, high-level language called Scala. Static types in Scala helps to prevent errors in complicated applications, and the JavaScript and JVM runtimes enable you to easily access the vast ecosystems of libraries for building high-performance systems.

Where is Scala used most frequently?

A developer must constantly be in demand. Better work and career opportunities are Scala's primary uses and reasons. Your demand will rise, and your marketability will grow if you learn Scala. Scala is used by numerous businesses, including Twitter, LinkedIn, Foursquare, etc.

Is Scala suitable for developing websites?

Because of its precise grammar, Scala reduces boilerplate code. In comparison to Java-based counterparts, Scala programmes need less code. It is both a functional language and an object-oriented language. Scala is an excellent choice for web development because of this mix.

Why is Scala more rapid than Java?

JVM supports both Scala and Java. Therefore, before running on JVM, their code needs to be compiled into bytecode. However, the Scala compiler supports the tail call recursion optimization method. The optimization speeds up the compilation of Scala code compared to Java code.

Why do we need Scala apps?

The main method is provided by the utility class App that Scala offers. Classes can extend the App class to create clear and executable programs in Scala rather than defining their main function.

Conclusion

In this article, we have gone through the Scala developers-Testing your Application in detail with topics like Matchers and Mockito.

Some related articles are as follows:

• Scala developers-Form submission and validation
   
• Scala developers-The Configuration API
   
• Scala developers-Asynchronous HTTP programming
   
• Scala developers-Application Settings
   

I suppose it is clear to you. Still, have doubts? Then please comment.

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