Why TestNG's beforeSuite only provides a value for one class while the other class gets null?

Question

I have a problem with the BeforeSuite annotation in TestNG. I want to initialize some variables in beforeSuite() so all the classes could use them directly. Only class A can get the value. Class B can't; it gets null.

Base.java:

public class Base {
    public String name;
    @BeforeSuite
    public void beforeSuite(){
        name = "stackoverflow";
    }
}

A.java:

public class A extends Base{
    @Test
    public void test(){
        System.out.println("A name:" + name);
    }

}

B.java

public class B extends Base{
    @Test
    public void test(){
        System.out.println("B name:" + name);
    }

}

textng.xml:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
<suite name="suite1" parallel="classes" thread-count="1" preserve-order="true">
   <test name="testValue">
        <classes>
            <class name="A"/>
            <class name="B"/>
        </classes>
    </test>
</suite>

test result:

mvn clean test
.
.
.
[INFO] Running TestSuite
B name:null
A name:stackoverflow

My TestNG version is 6.8.8.

Answer 1

The problem lies in the test code. You have a common base class that is being extended by multiple child classes and within the base class you have a @BeforeSuite method.

TestNG by behavior, guarantees that the @BeforeSuite method gets executed ONLY once per <suite> tag.

In your case, it already got invoked for class A and so it will be skipped for class B which explains the NullPointerException.

To fix this, you would need to move your initialization to either a @BeforeMethod or @BeforeClass annotated method.