JUnit setUp doesn't create object-CodePudding

Why do I get a NullPointerExeption for testManuscript when trying to run my test?

This is my Manuscript.java:

package org.lhoffjann;


public class Manuscript {
private String msID;
private String path;
    public void setMSid(String msID){
        this.msID = msID;
    }

    public String getMSid() {
        return this.msID;
    }
}

This is my ManuscriptTest.java:

package org.lhoffjann;

import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class ManuscriptTest {
    private static Manuscript testManuscript;

    @Before
    public void setUp(){
        testManuscript = new Manuscript();
    }
    @Test
    public void testGetMSid() {
        testManuscript.setMSid("1234");
        assertTrue("1234" == testManuscript.getMSid());
    }
}

CodePudding user response：

You have imported @Test from JUnit 5, while you're using @Before from JUnit 4, that combination doesn't work. You need to choose which JUnit version you want to use, 4 or 5, and then consistently import classes from that JUnit version. I would recommend using JUnit 5, and removing all JUnit 4 dependencies from your classpath, or at least configure your IDE to not suggest those imports.

For this specific case, replace @Before (org.junit.Before) with @BeforeEach (org.junit.jupiter.api.BeforeEach).

In the example as shown, you don't even need this setUp method, as each test-execution gets its own instance of the test class. You can use:

private Manuscript testManuscript = new Manuscript();

That is, remove static, initialize the field directly, and remove the setUp method.

Even if you continue to use the setUp method, I recommend removing the static, so testManuscript is an instance field, like it is actually used.

CodePudding user response：

You have mixed Junit4 with Junit5. You should use only one version.

Junit4 or

package org.lhoffjann;

import org.junit.Before;
import org.junit.Test;

import org.junit.Assert;

public class ManuscriptTest {
    private static Manuscript testManuscript;

    @Before
    public void setUp(){
        testManuscript = new Manuscript();
    }
    
    @Test
    public void testGetMSid() {
        testManuscript.setMSid("1234");
       Assert.assertEquals("1234",testManuscript.getMSid());
    }

Junit5

package org.lhoffjann;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

class ManuscriptTest {
    private static Manuscript testManuscript;

    @BeforeEach
    public void setUp() {
        testManuscript = new Manuscript();
    }

    @Test
    void testGetMSid() {
        testManuscript.setMSid("1234");
        Assertions.assertEquals("1234", testManuscript.getMSid());
    }
}