NPE when layer name does not exists

[simasch]

I made a mistake in my layeredArchitecture definition. There is no layer called control:

   @ArchTest
    public static final ArchRule layerRule = layeredArchitecture()
            .layer("boundary").definedBy("..boundary..")
            .layer("service").definedBy("..control.service..")
            .layer("repository").definedBy("..control.repository..")
            .layer("entity").definedBy("..entity..")

            .whereLayer("boundary").mayNotBeAccessedByAnyLayer()
            .whereLayer("repository").mayOnlyBeAccessedByLayers("boundary", "control")
            .whereLayer("service").mayOnlyBeAccessedByLayers("boundary")
            .whereLayer("entity").mayOnlyBeAccessedByLayers("boundary", "control");

When I execute the test I get a NPE:

java.lang.NullPointerException
	at com.tngtech.archunit.library.Architectures$LayeredArchitecture$LayerDefinition.access$500(Architectures.java:229)
	at com.tngtech.archunit.library.Architectures$LayeredArchitecture.packagesOf(Architectures.java:218)
	at com.tngtech.archunit.library.Architectures$LayeredArchitecture.evaluate(Architectures.java:151)
	at com.tngtech.archunit.lang.ArchRule$Assertions.check(ArchRule.java:79)
	at com.tngtech.archunit.library.Architectures$LayeredArchitecture.check(Architectures.java:174)
	at com.tngtech.archunit.junit.ArchRuleExecution.evaluateOn(ArchRuleExecution.java:57)
	at com.tngtech.archunit.junit.ArchUnitRunner.runChild(ArchUnitRunner.java:134)
	at com.tngtech.archunit.junit.ArchUnitRunner.runChild(ArchUnitRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at com.tngtech.archunit.junit.ArchUnitRunner$1.evaluate(ArchUnitRunner.java:73)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

It would be great to print a meaningful error message instead of the NPE.

[codecholeric]

You're absolutely right, I'll look into that right away and add a meaningful error message!!