JUnit test fails when method arg is annotated @Nonnull

Question

Can someone explain me why my JUnit test fail:

• notNullMethodTest() uses @NotNull --> success
• nonnullMethodTest() uses @Nonnull --> fail

Unexpected exception, expected<java.lang.NullPointerException> but was<java.lang.IllegalArgumentException>

package com;

import java.util.Objects;

import javax.annotation.Nonnull;
import javax.validation.constraints.NotNull;

import org.junit.Test;

public class AnnotationTest {
  private void nonnullMethod(@Nonnull String arg) {
    Objects.requireNonNull(arg);
  }

  @Test(expected = NullPointerException.class)
  public void nonnullMethodTest() {
    nonnullMethod(null);
  }

  private void notNullMethod(@NotNull String arg) {
    Objects.requireNonNull(arg);
  }

  @Test(expected = NullPointerException.class)
  public void notNullMethodTest() {
    notNullMethod(null);
  }
}

Here the StackTrace:

java.lang.Exception: Unexpected exception, expected<java.lang.NullPointerException> but was<java.lang.IllegalArgumentException>

    at org.junit.internal.runners.statements.ExpectException.evaluate(ExpectException.java:28)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.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$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:237)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: java.lang.IllegalArgumentException: Argument for @Nonnull parameter 'arg' of com/AnnotationTest.nonnullMethod must not be null
    at com.AnnotationTest.$$$reportNull$$$0(AnnotationTest.java)
    at com.AnnotationTest.nonnullMethod(AnnotationTest.java)
    at com.AnnotationTest.nonnullMethodTest(AnnotationTest.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.ExpectException.evaluate(ExpectException.java:19)
    ... 19 more

Thanks

Answer 1

IntelliJ has recently started generating this assertion code by default. If you don't want this behavior, you can deactivate it in the compiler settings:

The configuration behind the "configure annotations" button allows you to specify which annotations should be taken into account. This is why it behaves differently when you switch annotations.