在 JUnit 或 TestNG 的两个测试类之间共享 Object

Question

Forgive the elementary question, I am learning Java still so need some advice on best practice here. I have a valid scenario where I wish to share the same object between two distinct Test classes using JUnit or TestNG. I understand that tests/test classes should not usually share state but this is a long-running journey.

I understand the JVM executes for both frameworks in this order:

1. @BeforeClass
2. Construcor call
3. @Before
4. @Test

Given I have an Person class with one field name and one getter & setter for same and I instantiate an instance of it in one Test Class:

public class FirstPersonTest {

    private Person firstPerson;

    @BeforeClass
    private void setup() {
        firstPerson = new Person("Dave");
    }

    @Test
    public void testName() {
        assertEquals("Dave", firstPerson.getName());
    }
}

And a second Test class:

public class SecondPersonTest {

    private Person firstPerson;
    private static String name;

    @BeforeClass
    private void setup(){
        name = firstPerson.getName(); //null pointer, firstPerson reference no longer exists from FirstPersonTest
    }

    @Test
    public void testName(){
        assertEquals("Dave", name);
    }
}

What is the optimal way of accessing the firstPerson object in the second class? I don't want to instantiate it a second time because I wish to share state for a journey test.

I want to be able to pass firstPerson instance in the constructor or an annotated setup method, but don't wish to instantiate the SecondPersonTest within the body of FirstPersonTest

Answer 1

You can use a singleton class for this purpose.

public class LocalStorage {
    private static volatile LocalStorage instance;
    private Map<String, Object> data = new HashMap<>();

    private LocalStorage() {
    }

    public static LocalStorage getInstance() {
        if (instance == null) {

            synchronized (LocalStorage.class) {
                if (instance == null) {
                    instance = new LocalStorage();
                }
            }
        }

        return instance;
    }

    public static void addData(String key, Object value) {
        getInstance().data.put(key, value);
    }

    public static Object getData(String key) {
        return getInstance().data.get(key);
    }

    public static <T> T getData(String key, Class<T> clazz) {
        return clazz.cast(getInstance().data.get(key));
    }
}

You can store the whole Person object or only the name field of the Person object.

To store:

Person firstPerson = new Person("Dave");
LocalStorage.addData("Dave", firstPerson);

To get it back:

Person firstPerson = LocalStorage.getData("Dave", Person.class);