Using JUnit on code that terminates [duplicate]

Question

I am trying to test a given java application, and for that purpose I want to use JUnit.

The problem I am facing is the following: Once the code I am trying to test finishes its work, its calling System.exit(), which closes the application. Although it is also stoping my tests from completing, as it closes the JVM (I assume).

Is there anyway to go around this problem, without modifying the original code? Initially I tried launching the application im testing from new thread, although that obviously didn't make much difference.

Answer 1

You can use System Rules: "A collection of JUnit rules for testing code which uses java.lang.System."

Among their rules, you have ExpectedSystemExit, below is an example on how to use it. I believe it is a very clean solution.

import org.junit.Rule;
import org.junit.Test;
import org.junit.contrib.java.lang.system.Assertion;
import org.junit.contrib.java.lang.system.ExpectedSystemExit;

public class SystemExitTest {
    @Rule
    public final ExpectedSystemExit exit = ExpectedSystemExit.none();

    @Test
    public void noSystemExit() {
        //passes
    }

    @Test
    public void executeSomeCodeAFTERsystemExit() {
        System.out.println("This is executed before everything.");
        exit.expectSystemExit();
        exit.checkAssertionAfterwards(new Assertion() {
            @Override
            public void checkAssertion() throws Exception {
                System.out.println("This is executed AFTER System.exit()"+
                " and, if exists, the @org.junit.After annotated method!");
            }
        });
        System.out.println("This is executed right before System.exit().");
        System.exit(0);
        System.out.println("This is NEVER executed.");
    }

    @Test
    public void systemExitWithArbitraryStatusCode() {
        exit.expectSystemExit();
        System.exit(0);
    }

    @Test
    public void systemExitWithSelectedStatusCode0() {
        exit.expectSystemExitWithStatus(0);
        System.exit(0);
    }

    @Test
    public void failSystemExit() {
        exit.expectSystemExit();
        //System.exit(0);
    }

}

If you use maven, you can add this to your pom.xml:

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.11</version>
</dependency>
<dependency>
    <groupId>com.github.stefanbirkner</groupId>
    <artifactId>system-rules</artifactId>
    <version>1.3.0</version>
</dependency>