How to make sure TestNG runs methods on test classes in succession instead of interleaved?

Question

The situation and the problem

I have several test classes, each with several test methods. All tests use the same test database in the background. Each test class

Answer 1

We were running into this same issue, most people say it's caused by using dependsOn, but our solution was just setting priorities at a test level for some of our tests. I set up a Test Listener to re-prioritize our tests so that they run in the correct order. This is based on saberduck's solution in https://github.com/cbeust/testng/issues/106

This solution will preserve the test priority by concatenating it to the class priority.

package testng_Listeners;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.HashMap;
import org.testng.IAnnotationTransformer;
import org.testng.Reporter;
import org.testng.annotations.ITestAnnotation;

//Listener to fix TestNG Interleaving issue. I had to re-write this as the original example I had did not allow for priority to be manually set on a test level.
public class RePrioritizingListener implements IAnnotationTransformer {

HashMap priorityMap = new HashMap();
Integer class_priorityCounter = 10000;
// The length of the final priority assigned to each method.
Integer max_testpriorityLength = 4;

@Override
public void transform(ITestAnnotation annotation, Class testClass, Constructor testConstructor, Method testMethod) {


// class of the test method.
Class declaringClass = testMethod.getDeclaringClass();
// Current priority of the test assigned at the test method.
Integer test_priority = annotation.getPriority();
// Current class priority.
Integer current_ClassPriority = priorityMap.get(declaringClass);

if (current_ClassPriority == null) {
    current_ClassPriority = class_priorityCounter++;
    priorityMap.put(declaringClass, current_ClassPriority);
}

String concatenatedPriority = test_priority.toString();

// Adds 0's to start of this number.
while (concatenatedPriority.length() < max_testpriorityLength) {
    concatenatedPriority = "0" + concatenatedPriority;
}

// Concatenates our class counter to the test level priority (example
// for test with a priority of 1: 1000100001; same test class with a
// priority of 2: 1000100002; next class with a priority of 1. 1000200001)
concatenatedPriority = current_ClassPriority.toString() + concatenatedPriority;

//Sets the new priority to the test method.
annotation.setPriority(Integer.parseInt(concatenatedPriority));

String printText = testMethod.getName() + " Priority = " + concatenatedPriority;
Reporter.log(printText);
System.out.println(printText);

}
}

Also you'll need to add the listener to your testng.xml