在单个Java类的命令行中使用JUnit编译并运行测试

Question

I have a simple problem I don't know how to solve!

I have a single Java file User.java :

import java.util.Vector;

public class User {
    private String name;
    private Vector<User> friends;

    public User(String name) {
        this.name = name;
        this.friends = new Vector<>();
    }

    public void addFriend(User newfriend) {
        friends.add(newfriend);
    }

    public boolean isFriendsWith(User friend) {
        return friends.indexOf(friend) != -1;
    }
}

and I have a simple test class UserTest.java beside this class:

import static org.junit.Assert.assertEquals;
import org.junit.Test;


public class UserTest {
    @Test
    public void evaluatesExpression() {
        User user = new User("foo");
        User user2 = new User("bar");
        user.addFriend(user2);
        assertEquals(true, user.isFriendsWith(user2));
    }
}

I want to run this test class for the User class. I'm not using IDEs like IntelliJ or Eclipse, so I want to compile the test from linux command line, but this command:

javac -cp .:"/usr/share/java/junit.jar" UserTest.java

gives me the following errors:

UserTest.java:1: error: package org.junit does not exist
import static org.junit.Assert.assertEquals;
                       ^
UserTest.java:1: error: static import only from classes and interfaces
import static org.junit.Assert.assertEquals;
^
UserTest.java:2: error: package org.junit does not exist
import org.junit.Test;
                ^
UserTest.java:6: error: cannot find symbol
    @Test
     ^
  symbol:   class Test
  location: class UserTest
UserTest.java:11: error: cannot find symbol
       assertEquals(true, user.isFriendsWith(user2));
        ^
  symbol:   method assertEquals(boolean,boolean)
  location: class UserTest
5 errors

Note: everything I have seen on Stackoverflow is about testing a single file in a project or building and testing with gradle and ..., but I don't know much about Java and I don't need to know much, I just need to know the simplest way to create and run a test for a single Java class.

Note2: I have installed junit with apt install junit and it installed junit-3-8-2 version.

Note3: I have problems when trying to compile my test class, I haven't even reached the stage where I can run the tests!

Answer 1

After quite a lot of trial and error in the comments section, the root cause was an old JUnit 3.8.2 dependency. The 3.x releases used a different namespace that was changed in 4.x to org.junit .

Therefore the classes where not found while compiling the test.

To debug such issues unzipping the jar with unzip on Linux can be helpful.