How do I share state between JUnit tests?

Question

I have a test class extending junit.framework.TestCase with several test methods.Each method opens a HTTP connection to server and exchange request and response json strings.One method gets a response with a string called UID(similar to sessionId) which i need to use in subsequent requests to the server.

I was previously writing that string to a file and my next requests read that file for string.I am running one method at a time.Now I am trying to use that string without file operations.I maintained a hastable(because there are many UIDs to keep track of) in my test class as instance variable for the purpose , but eventually found that class is getting loaded for my each method invocation as my static block is executing everytime.This is causing the loss of those UIDs.

How do I achieve this without writing to file and reading from it?

I doubt whether my heading matches my requirement.Someone please edit it accordingly.

Answer 1

You will need a static variable for this because each test gets its own instance of the test class.

Use this pattern:

private static String uuid;

private void login() {
    // Run this only once
    if (null != uuid) return;

    ... talk to your server ...
    uuid = responseFromServer.getUuid();
}

@Test
public void testLogin() {
    login();
    assertNotNull( uuid );
}

@Test
public void someOtherTest() {
    login();

    ... test something else which needs uuid ...
}

@Test
public void testWithoutLogin() {
    ... usual test code ...
}

This approach makes sure that login() is called for each test that needs it, that it's tested on its own and that you can run each test independently.

Answer 2

JUnit will create a new instance of the class for each test. Consequently you should likely set up and store this info as static to the class, using a @BeforeClass annotated static method.

See this SO answer for more info.