TestNG 拦截TestClassConstructor 模拟

Question

I need somehow to intercept Test class constructor to override a behavior. In JUnit , it is done with:

@Override
public <T> T interceptTestClassConstructor(Invocation<T> invocation,
                                           ReflectiveInvocationContext<Constructor<T>> invocationContext,
                                           ExtensionContext extensionContext) throws Throwable {
...
}

How is this achievable in TestNG?

Answer 1

You could override the behavior using IObjectFactory .

public class CustomObjectFactory implements IObjectFactory {

    @Override
    public Object newInstance(Constructor constructor, Object... params) {
        if(constructor.getDeclaringClass().equals(YourTestCalss.class)) {
            return yourCustomObject();
        }

        try {
            return constructor.newInstance(params);
        } catch(InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
            // error handling...
        }
    
        return null; // or any other object or throw exception
    }
}

Now in a test class, add a method as below:

@Test
public class YourTestClass {
    // ......
    // test methods
    // ......


    @ObjectFactory
    public ITestObjectFactory getObjectFactory() {
        return new CustomObjectFactory();
    }
}

Please note that even though this method is declared inside YourTestClass , this same object factory would be used for every other test class in your suite. Hence the if condition to check the class is required in CustomObjectFactory.newInstance .

You may also try IObjectFactory2 which has a newInstance method taking Class as the parameter.

---

TestNG has an implementation for IObjectFactory -> ObjectFactoryImpl . You could use extends ObjectFactoryImpl instead, in which case the code within the `newInstance could be:

if(constructor.getDeclaringClass().equals(YourTestCalss.class)) {
    return yourCustomObject();
}
return super.newInstance(constructor, params);

BUT note that, Since ObjectFactoryImpl is inside the testng.internal package, I assume that extending ObjectFactoryImpl is not recommended.

Answer 2

As discuss in mailing group , @KrishnanMahadevan fixed a bug which will allow to intercept Test class constructor in version 7.5

public class LocalSuiteAlteringListener implements IAlterSuiteListener { @Override public void alter(List<XmlSuite> suites) { suites.forEach(each -> each.setObjectFactoryClass(MyFactory.class));