1. Testing



The standard source locations for testing are:

  • Scala sources in src/test/scala/
  • Java sources in src/test/java/
  • Resources for the test classpath in src/test/resources/

The resources may be accessed from tests by using the getResource methods of java.lang.Class or java.lang.ClassLoader.

The main Scala testing frameworks ( ScalaCheck, ScalaTest, and specs2) provide an implementation of the common test interface and only need to be added to the classpath to work with sbt. For example, ScalaCheck may be used by declaring it as a managed dependency:

lazy val scalacheck = "org.scalacheck" %% "scalacheck" % "1.17.0"
libraryDependencies += scalacheck % Test

Test is the configuration and means that ScalaCheck will only be on the test classpath and it isn’t needed by the main sources. This is generally good practice for libraries because your users don’t typically need your test dependencies to use your library.

With the library dependency defined, you can then add test sources in the locations listed above and compile and run tests. The tasks for running tests are test and testOnly. The test task accepts no command line arguments and runs all tests:

> test


The testOnly task accepts a whitespace separated list of test names to run. For example:

> testOnly org.example.MyTest1 org.example.MyTest2

It supports wildcards as well:

> testOnly org.example.*Slow org.example.MyTest1


The testQuick task, like testOnly, allows to filter the tests to run to specific tests or wildcards using the same syntax to indicate the filters. In addition to the explicit filter, only the tests that satisfy one of the following conditions are run:

  • The tests that failed in the previous run
  • The tests that were not run before
  • The tests that have one or more transitive dependencies, maybe in a different project, recompiled.
Tab completion 

Tab completion is provided for test names based on the results of the last Test/compile. This means that a new sources aren’t available for tab completion until they are compiled and deleted sources won’t be removed from tab completion until a recompile. A new test source can still be manually written out and run using testOnly.

Other tasks 

Tasks that are available for main sources are generally available for test sources, but are prefixed with Test / on the command line and are referenced in Scala code with Test / as well. These tasks include:

  • Test / compile
  • Test / console
  • Test / consoleQuick
  • Test / run
  • Test / runMain

See Running for details on these tasks.


By default, logging is buffered for each test source file until all tests for that file complete. This can be disabled by setting logBuffered:

Test / logBuffered := false

Test Reports 

By default, sbt will generate JUnit XML test reports for all tests in the build, located in the target/test-reports directory for a project. This can be disabled by disabling the JUnitXmlReportPlugin

val myProject = (project in file(".")).disablePlugins(plugins.JUnitXmlReportPlugin)


Test Framework Arguments 

Arguments to the test framework may be provided on the command line to the testOnly tasks following a -- separator. For example:

> testOnly org.example.MyTest -- -verbosity 1

To specify test framework arguments as part of the build, add options constructed by Tests.Argument:

Test / testOptions += Tests.Argument("-verbosity", "1")

To specify them for a specific test framework only:

Test / testOptions += Tests.Argument(TestFrameworks.ScalaCheck, "-verbosity", "1")

Setup and Cleanup 

Specify setup and cleanup actions using Tests.Setup and Tests.Cleanup. These accept either a function of type () => Unit or a function of type ClassLoader => Unit. The variant that accepts a ClassLoader is passed the class loader that is (or was) used for running the tests. It provides access to the test classes as well as the test framework classes.

Note: When forking, the ClassLoader containing the test classes cannot be provided because it is in another JVM. Only use the () => Unit variants in this case.


Test / testOptions += Tests.Setup( () => println("Setup") )
Test / testOptions += Tests.Cleanup( () => println("Cleanup") )
Test / testOptions += Tests.Setup( loader => ... )
Test / testOptions += Tests.Cleanup( loader => ... )

Disable Parallel Execution of Tests 

By default, sbt runs all tasks in parallel and within the same JVM as sbt itself. Because each test is mapped to a task, tests are also run in parallel by default. To make tests within a given project execute serially: :

Test / parallelExecution := false

Test can be replaced with IntegrationTest to only execute integration tests serially. Note that tests from different projects may still execute concurrently.

Filter classes 

If you want to only run test classes whose name ends with “Test”, use Tests.Filter:

Test / testOptions := Seq(Tests.Filter(s => s.endsWith("Test")))

Forking tests 

The setting:

Test / fork := true

specifies that all tests will be executed in a single external JVM. See Forking for configuring standard options for forking. By default, tests executed in a forked JVM are executed sequentially. More control over how tests are assigned to JVMs and what options to pass to those is available with testGrouping key. For example in build.sbt:

import Tests._

  def groupByFirst(tests: Seq[TestDefinition]) =
    tests groupBy (_.name(0)) map {
      case (letter, tests) =>
        val options = ForkOptions().withRunJVMOptions(Vector("-Dfirst.letter"+letter))
        new Group(letter.toString, tests, SubProcess(options))
    } toSeq

    Test / testGrouping := groupByFirst( (Test / definedTests).value )

The tests in a single group are run sequentially. Control the number of forked JVMs allowed to run at the same time by setting the limit on Tags.ForkedTestGroup tag, which is 1 by default. Setup and Cleanup actions cannot be provided with the actual test class loader when a group is forked.

In addition, forked tests can optionally be run in parallel within the forked JVM(s), using the following setting:

Test / testForkedParallel := true

Additional test configurations 

You can add an additional test configuration to have a separate set of test sources and associated compilation, packaging, and testing tasks and settings. The steps are:

  • Define the configuration
  • Add the tasks and settings
  • Declare library dependencies
  • Create sources
  • Run tasks

The following two examples demonstrate this. The first example shows how to enable integration tests. The second shows how to define a customized test configuration. This allows you to define multiple types of tests per project.

Integration Tests 

The following full build configuration demonstrates integration tests.

lazy val scalatest = "org.scalatest" %% "scalatest" % "3.2.17"

ThisBuild / organization := "com.example"
ThisBuild / scalaVersion := "2.12.18"
ThisBuild / version      := "0.1.0-SNAPSHOT"

lazy val root = (project in file("."))
    libraryDependencies += scalatest % "it,test"
    // other settings here
  • configs(IntegrationTest) adds the predefined integration test configuration. This configuration is referred to by the name it.
  • settings(Defaults.itSettings) adds compilation, packaging, and testing actions and settings in the IntegrationTest configuration.
  • settings(libraryDependencies += scalatest % "it,test") adds scalatest to both the standard test configuration and the integration test configuration it. To define a dependency only for integration tests, use “it” as the configuration instead of “it,test”.

The standard source hierarchy is used:

  • src/it/scala for Scala sources
  • src/it/java for Java sources
  • src/it/resources for resources that should go on the integration test classpath

The standard testing tasks are available, but must be prefixed with IntegrationTest/. For example to run all integration tests:

> IntegrationTest/test

Or to run a specific test:

> IntegrationTest/testOnly org.example.AnIntegrationTest

Similarly the standard settings may be configured for the IntegrationTest configuration. If not specified directly, most IntegrationTest settings delegate to Test settings by default. For example, if test options are specified as:

Test / testOptions += ...

then these will be picked up by the Test configuration and in turn by the IntegrationTest configuration. Options can be added specifically for integration tests by putting them in the IntegrationTest configuration:

IntegrationTest / testOptions += ...

Or, use := to overwrite any existing options, declaring these to be the definitive integration test options:

IntegrationTest / testOptions := Seq(...)

Custom test configuration 

The previous example may be generalized to a custom test configuration.

lazy val scalatest = "org.scalatest" %% "scalatest" % "3.2.17"
lazy val FunTest = config("fun") extend(Test)

ThisBuild / organization := "com.example"
ThisBuild / scalaVersion := "2.12.18"
ThisBuild / version      := "0.1.0-SNAPSHOT"

lazy val root = (project in file("."))
    libraryDependencies += scalatest % FunTest
    // other settings here

Instead of using the built-in configuration, we defined a new one:

lazy val FunTest = config("fun") extend(Test)

The extend(Test) part means to delegate to Test for undefined FunTest settings. The line that adds the tasks and settings for the new test configuration is:


This says to add test and settings tasks in the FunTest configuration. We could have done it this way for integration tests as well. In fact, Defaults.itSettings is a convenience definition: val itSettings = inConfig(IntegrationTest)(Defaults.testSettings).

The comments in the integration test section hold, except with IntegrationTest replaced with FunTest and "it" replaced with "fun". For example, test options can be configured specifically for FunTest:

FunTest / testOptions += ...

Test tasks are run by prefixing them with fun:

> FunTest / test

Additional test configurations with shared sources 

An alternative to adding separate sets of test sources (and compilations) is to share sources. In this approach, the sources are compiled together using the same classpath and are packaged together. However, different tests are run depending on the configuration.

lazy val scalatest = "org.scalatest" %% "scalatest" % "3.2.17"
lazy val FunTest = config("fun") extend(Test)

ThisBuild / organization := "com.example"
ThisBuild / scalaVersion := "2.12.18"
ThisBuild / version      := "0.1.0-SNAPSHOT"

def itFilter(name: String): Boolean = name endsWith "ITest"
def unitFilter(name: String): Boolean = (name endsWith "Test") && !itFilter(name)

lazy val root = (project in file("."))
    libraryDependencies += scalatest % FunTest,
    Test / testOptions := Seq(Tests.Filter(unitFilter)),
    FunTest / testOptions := Seq(Tests.Filter(itFilter))
    // other settings here

The key differences are:

  • We are now only adding the test tasks (inConfig(FunTest)(Defaults.testTasks)) and not compilation and packaging tasks and settings.
  • We filter the tests to be run for each configuration.

To run standard unit tests, run test (or equivalently, Test / test):

> test

To run tests for the added configuration (here, "FunTest"), prefix it with the configuration name as before:

> FunTest / test
> FunTest / testOnly org.example.AFunTest
Application to parallel execution 

One use for this shared-source approach is to separate tests that can run in parallel from those that must execute serially. Apply the procedure described in this section for an additional configuration. Let’s call the configuration serial:

lazy val Serial = config("serial") extend(Test)

Then, we can disable parallel execution in just that configuration using:

Serial / parallelExecution := false

The tests to run in parallel would be run with test and the ones to run in serial would be run with Serial/test.


Support for JUnit5 is provided by sbt-jupiter-interface. To add JUnit Jupiter support into your project, add the jupiter-interface dependency in your project’s main build.sbt file.

libraryDependencies += "net.aichler" % "jupiter-interface" % "0.9.0" % Test

and the sbt-jupiter-interface plugin to your project/plugins.sbt

addSbtPlugin("net.aichler" % "sbt-jupiter-interface" % "0.9.0")

Support for JUnit4 is provided by junit-interface. Add the junit-interface dependency in your project’s main build.sbt file.

libraryDependencies += "com.github.sbt" % "junit-interface" % "0.13.3" % Test


This page describes adding support for additional testing libraries and defining additional test reporters. You do this by implementing sbt interfaces (described below). If you are the author of the testing framework, you can depend on the test interface as a provided dependency. Alternatively, anyone can provide support for a test framework by implementing the interfaces in a separate project and packaging the project as an sbt Plugin.

Custom Test Framework 

The main Scala testing libraries have built-in support for sbt. To add support for a different framework, implement the uniform test interface.

Custom Test Reporters 

Test frameworks report status and results to test reporters. You can create a new test reporter by implementing either TestReportListener or TestsListener.

Using Extensions 

To use your extensions in a project definition:

Modify the testFrameworks setting to reference your test framework:

testFrameworks += new TestFramework("custom.framework.ClassName")

Specify the test reporters you want to use by overriding the testListeners setting in your project definition.

testListeners += customTestListener

where customTestListener is of type sbt.TestReportListener.