How does TestNG priority work for a group?

Question

Suppose I have five test cases out of which three are grouped in "Smoke Testing" and two have not been grouped at all.

If I have set priority for all my test cases from 1 to 5, will the cases from smoke testing group be evoked in priority?

@Test (priority=3, groups={"Smoke Testing"})
p v Test1(){}
@Test (priority=1, groups={"Smoke Testing"})
p v Test2(){}
@Test (priority=2, groups={"Smoke Testing"})
p v Test3(){}
@Test (priority=5)
p v Test4(){}
@Test (priority=4)
p v Test5(){}

What will happen if I want to add another group XYZ and added test cases like:

@Test (priority=2, groups={"XYZ"})
p v Test6(){}
@Test (priority=1, groups={"XYZ"})
p v Test7(){}

Answer 1

I was created sample TestNG Class in which test cases are divided in 'Smoke test' and 'Regression' Groups.

package com.testNG;

import org.testng.annotations.AfterGroups;
import org.testng.annotations.BeforeGroups;
import org.testng.annotations.Test;

public class TestNG_Groups 
{
    @BeforeGroups("Smoke Test")
    public void setup() 
    {
        System.out.println("Launching URL");
    }

    @Test(groups={"Smoke Test"})
    public void method1() 
    {
        System.out.println("Method-1");
    }
    @Test(groups={"Smoke Test"})
    public void method2() 
    {
        System.out.println("Method-2");
    }

    @Test(groups={"Smoke Test"})
    public void method3() 
    {
        System.out.println("Method-3");
    }

    @AfterGroups("Smoke Test")
    public void runfinal1() 
    {
        System.out.println("Smoke Test End..");
    }

    @Test(groups={"Regression"})
    public void method5() 
    {
        System.out.println("Method-5");
    }
    @Test(groups={"Regression"})
    public void method6() 
    {
        System.out.println("Method-6");
    }
    @AfterGroups("Regression")
    public void runfinal2() 
    {
        System.out.println("Regression Test End..");
    }

    @Test(dependsOnGroups = {"Smoke Test","Regression"})
    public void tearDown() 
    {
        System.out.println("Closing Browser");
    }

}

OUTPUT:

Launching URL
Method-1
Method-2
Method-3
Smoke Test End..
Method-5
Method-6
Regression Test End..
Closing Browser
PASSED: method1
PASSED: method2
PASSED: method3
PASSED: method5
PASSED: method6
PASSED: tearDown

===============================================
    Default test
    Tests run: 6, Failures: 0, Skips: 0
===============================================

---

Answer 2

TestNG doesn't care about groups at runtime. Then, it will only follow priority.

Groups are used for the test selection/filtering.

In other words: TestNG will always follow priority on selected tests and groups are a way to change the test selection.

Answer 3

Here is my version of story.

@Test(priority=2, groups={"Smoke"})
public void Test1(){
    System.out.println("Test 1 -priority=2, Smoke");
}
@Test(priority=4, groups={"Smoke"})
public void Test2(){
    System.out.println("Test 2 -priority=4, Smoke");
}
@Test(priority=1, groups={"Smoke"})
public void Test3(){
    System.out.println("Test 3 -priority=1, Smoke");
}
@Test(priority=2, groups={"Reg"})
public void Test4(){
    System.out.println("Test 4 -priority=2, Reg");
}
@Test(priority=3, groups={"Reg"})
public void Test5(){
    System.out.println("Test 5 -priority=3, Reg");
}
@Test(priority=4, groups={"Reg"})
public void Test6(){
    System.out.println("Test 6 -priority=4, Reg");
}
@Test
public void Test7(){
    System.out.println("Test 7");
}

The output is well explanatory and explains everything. The output is:

Test 7
Test 3 -priority=1, Smoke
Test 1 -priority=2, Smoke
Test 4 -priority=2, Reg
Test 5 -priority=3, Reg
Test 2 -priority=4, Smoke
Test 6 -priority=4, Reg

Answer 4

As evidenced by NiNa's answer above: Answer, Priority always takes precedence and it overrides the group mechanism (and as such, dependencies). If there are two methods with the same priority, the first one that goes is in alphabetical order. Additionally, and a little off topic, is that preserve-order in your TestNG.xml file seems to be the last of all the ordering mechanisms that is adhered, and behaves strangely (can't figure it out yet) when mixed with groups / priorities.