_PrivateMethodをscalatestでテストする.md

PrivateMethodをscalatestでテストする

$sbt test
[info] welcome to sbt 1.5.1 (Oracle Corporation Java 15)
[info] loading settings for project global-plugins from plugins.sbt ...
[info] loading global plugins from /Users/arata/.sbt/1.0/plugins
[info] loading project definition from /Users/arata/Documents/Workspace/scala/scalatest/project
[info] loading settings for project root from build.sbt ...
[info] set current project to scalameter-getting-started (in build file:/Users/arata/Documents/Workspace/scala/scalatest/)
[info] TestSpec:
[info] test
[info] - addPositiveNumber
[info] - addOne
[info] - minusOne
[info] Run completed in 247 milliseconds.
[info] Total number of tests run: 3
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 3, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.

Ref

• https://www.scalatest.org/user_guide/using_PrivateMethodTester

build.sbt

val commonSettings = Seq(
  version := "0.1-SNAPSHOT",
  scalaVersion := "2.13.6",
  scalacOptions ++= Seq(
    "-deprecation",
    "-feature",
    "-unchecked",
    "-language:implicitConversions",
    "-Xlint",
    "-Xfatal-warnings",
    "-Ywarn-numeric-widen",
    "-Ywarn-unused",
    "-Ywarn-unused:imports",
    "-Ywarn-value-discard"
  )
)

lazy val root = (project in file("."))
  .settings(commonSettings)
  .settings(
    name := "scalameter-getting-started",
    libraryDependencies ++= Seq(
        "org.scalatest" %% "scalatest" % "3.2.9"
    )
  )

Test.scala

import org.scalatest.PrivateMethodTester
import org.scalatest.freespec.AnyFreeSpec

class TestSpec extends AnyFreeSpec with PrivateMethodTester {
  "test" - {
    val t = new Test()
    "addPositiveNumber" in {
      assert(t.addPositiveNumber(10, 10) == 20)
    }

    val addOne = PrivateMethod[Int](Symbol("addOne"))
    "addOne" in {
      assert(t.invokePrivate(addOne(10)) == 11)
    }

    val minusOne = PrivateMethod[Int](Symbol("minusOne"))
    "minusOne" in {
      assert(t.invokePrivate(minusOne(10)) == 9)
    }

  }
}

class Test {
  def addPositiveNumber(x: Int, y: Int): Int = if (y <= 0) {
    x
  } else {
    addPositiveNumber(addOne(x), minusOne(y))
  }

  private def addOne(x: Int): Int = x + 1

  private def minusOne(x: Int): Int = x - 1
}