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A SBT plugin to use ScalaTest with scripted-plugin to test your SBT plugins

Traditionally, to test a SBT plugin, you had to create subprojects in /sbt-test, then in the subprojects, create SBT tasks to perform the testing, then specify the tasks to execute in a test file (see http://www.scala-sbt.org/0.13/docs/Testing-sbt-plugins.html).

This is fine when performing simple tests, but for complicated tests (see http://www.scala-sbt.org/0.13/docs/Testing-sbt-plugins.html#step+6%3A+custom+assertion), this can get messy really quickly:

• It sucks to not be able to write tests in a BDD style (except by using comments, which feels clunky).
• Manually writing code to print the test results to the console for each subproject is a pain.

This plugin leverages ScalaTest's powerful assertion system (to automatically print useful messages on assertion failure) and its expressive DSLs.

This plugin allows you to use any of ScalaTest's test Suites, including AsyncTestSuites.

• Do not use ScalaTest's ParallelTestExecution mixin with this plugin. ScriptedScalaTestSuiteMixin runs sbt clean before each test, which may cause weird side effects when run in parallel.
• When executing SBT tasks in tests, use Project.runTask(<task>, state.value) instead of <task>.value. Calling <task>.value declares it as a dependency, which executes before the tests, not when the line is called.
• When implementing BeforeAndAfterEach's beforeEach, make sure to invoke super.beforeEach afterwards:

override protected def beforeEach(): Unit = {
  // ...
  super.beforeEach() // To be stackable, must call super.beforeEach
}

• This SBT plugin is now tested using itself!

Add the following to your main project's project/scripted.sbt (create file it if doesn't exist):

libraryDependencies += { "org.scala-sbt" % "scripted-plugin" % sbtVersion.value }

libraryDependencies += { "org.scala-sbt" %% "scripted-plugin" % sbtVersion.value }

Note the %% operator.

Not Required

Recommended settings by SBT:

// build.sbt
ScriptedPlugin.scriptedSettings
scriptedLaunchOpts := { scriptedLaunchOpts.value ++
  Seq("-Xmx1024M", "-XX:MaxPermSize=256M", "-Dplugin.version=" + version.value)
}
scriptedBufferLog := false

If you are using sbt-cross-building (SBT < 0.13.6), don't add scripted-plugin to project/scripted.sbt, and replace ScriptedPlugin.scriptedSettings in build.sbt with CrossBuilding.scriptedSettings.

// build.sbt
lazy val root = (project in file("."))
  .settings(
    name := "sbt-something",
    scriptedLaunchOpts := { scriptedLaunchOpts.value ++
      Seq("-Xmx1024M", "-Dplugin.version=" + version.value)
    },
    scriptedBufferLog := false
  )

// build.sbt
lazy val root = (project in file("."))
  .enablePlugins(SbtPlugin)
  .settings(
    name := "sbt-something",
    scriptedLaunchOpts := { scriptedLaunchOpts.value ++
      Seq("-Xmx1024M", "-Dplugin.version=" + version.value)
    },
    scriptedBufferLog := false
  )

Create the test subproject in sbt-test/<test-group>/<test-name>.

Include your plugin in the build.

See http://www.scala-sbt.org/0.13/docs/Testing-sbt-plugins.html#step+3%3A+src%2Fsbt-test for an example.

Add the following to your sbt-test/<test-group>/<test-name>/project/plugins.sbt:

addSbtPlugin("com.github.daniel-shuy" % "sbt-scripted-scalatest" % "1.1.1")

Override the scalatest dependency version with the version of ScalaTest you wish to use:

addSbtPlugin("com.github.daniel-shuy" % "sbt-scripted-scalatest" % "1.1.1")
libraryDependencies += "org.scalatest" %% "scalatest" % "3.0.5"

Put only the following in the sbt-test/<test-group>/<test-name>/test script file:

> scriptedScalatest

In sbt-test/<test-group>/<test-name>/build.sbt, create a new ScalaTest Suite/Spec, mixin ScriptedScalaTestSuiteMixin and pass it into scriptedScalaTestSpec. When mixing in ScriptedScalaTestSuiteMixin, implement sbtState as state.value.

Using SBT's Example in http://www.scala-sbt.org/0.13/docs/Testing-sbt-plugins.html#step+6%3A+custom+assertion:

import com.github.daniel.shuy.sbt.scripted.scalatest.ScriptedScalaTestSuiteMixin
import org.scalatest.Assertions._
import org.scalatest.wordspec.AnyWordSpec

lazy val root = (project in file("."))
  .settings(
    version := "0.1",
    scalaVersion := "2.10.6",
    assemblyJarName in assembly := "foo.jar",

    scriptedScalaTestSpec := Some(new AnyWordSpec with ScriptedScalaTestSuiteMixin {
      override val sbtState: State = state.value

      "assembly" should {
        "create a JAR that prints out 'hello'" in {
          Project.runTask(Keys.assembly, sbtState)
          val process = sbt.Process("java", Seq("-jar", (crossTarget.value / "foo.jar").toString))
          val out = (process!!)
          assert(out.trim == "bye")
        }
      }
    }
  )

It is possible move the ScalaTest Suite/Spec into a separate .scala file in the project folder, however that may cause issues when trying to access SBT SettingKeys or declaring custom TaskKeys, therefore is currently not recommended except for extremely simple tests. A better approach would be to move all configurations related to this plugin to a new .sbt file, eg. test.sbt.

See Settings for other configurable settings.

Append -SNAPSHOT to the main project version before running scripted-plugin.

Eg. Run sbt scripted on the main project to execute all tests.