Test that produces no highlights

ExampleMatcher.scala

import com.intellij.codeInspection.{LocalInspectionTool, LocalInspectionToolSession, ProblemHighlightType, ProblemsHolder}
import com.intellij.psiPsiElementVisitor
import org.jetbrains.annotations.NotNull
import org.jetbrains.plugins.scala.lang.psi.api.ScalaElementVisitor
import org.jetbrains.plugins.scala.lang.psi.api.expr.ScMethodCall

class ExampleMatcher extends LocalInspectionTool {
  @NotNull override def buildVisitor(@NotNull holder: ProblemsHolder, isOnTheFly: Boolean, session: LocalInspectionToolSession): PsiElementVisitor = {
    buildVisitor(holder, isOnTheFly)
  }
  @NotNull override def buildVisitor(@NotNull holder: ProblemsHolder, isOnTheFly: Boolean): PsiElementVisitor = {
    new ScalaElementVisitor {
      override def visitMethodCallExpression(call: ScMethodCall) = {
        super.visitMethodCallExpression(call)
        holder.registerProblem(call, "I just want a highlight", ProblemHighlightType.ERROR)
      }
    }
  }
}

FixtureTest.scala

import com.intellij.codeInspection.LocalInspectionTool
import com.intellij.openapi.fileTypes.LanguageFileType
import com.intellij.psi.PsiFile
import com.intellij.testFramework.fixtures.{CodeInsightTestFixture, IdeaProjectTestFixture, IdeaTestFixtureFactory, TestFixtureBuilder}
import com.intellij.testFramework.UsefulTestCase
import com.iterable.hud.tests.util.TestUtils
import org.jetbrains.plugins.scala.ScalaFileType
import org.junit.Assert

class FixtureTest extends UsefulTestCase {
  val inspectionClass: Class[_ <: LocalInspectionTool] = classOf[ExampleMatcher]
  val fileType: LanguageFileType = ScalaFileType.INSTANCE
  val fixtureFactory = IdeaTestFixtureFactory.getFixtureFactory
  var fixtureBuilder: TestFixtureBuilder[IdeaProjectTestFixture] = _
  var fixture: CodeInsightTestFixture = _
  var psiFile: PsiFile = _

  override def setUp(): Unit = {
    super.setUp()
    fixtureBuilder = fixtureFactory.createFixtureBuilder(this.getName)
    val tmpFixture = fixtureBuilder.getFixture
    fixture = fixtureFactory.createCodeInsightFixture(tmpFixture)
    fixture.setUp()
    fixture.setTestDataPath(TestUtils.getTestDataPath)
    val testDataFile = getTestData()
    psiFile = fixture.configureByFile(testDataFile)
    fixture.enableInspections(inspectionClass)
  }
  
  def testIsThisThingOn(): Unit = {
    val highlights = fixture.doHighlighting()
    Assert.assertNotEquals("Should have highlights.", highlights.size(), 0)
  }

  def getTestData(): String = {
    "/path/to/fixture"
  }
}