Grouping causes ClassB to run before ClassA finishes

[GoogleCodeExporter]

What steps will reproduce the problem?
1.  Create 2 Test classes
2.  Add testMethodA and testMethod C to class 1
3.  Add testMethodB and testMethodD to class 2
4.  Add the same group to all 4 test methods
5.  Setup xml file to run all tests in package and include only the group 
specified

What is the expected output? What do you see instead?
Would expect to see the following flow:

@BeforeSuite
@BeforeTest
@BeforeClass - class1
@AfterClass - class 1
@BeforeClass - class 2
@AfterClass - class 2
@AfterTest
@AfterSuite

but get this flow :

@BeforeSuite
@BeforeTest
@BeforeClass - class 1
@BeforeClass - class 2
@AfterClass - class 1
@AfterClass - class 2
@AfterTest
@AfterSuite

What version of the product are you using? On what operating system?
TestNG 6.8.5

Please provide any additional information below.

It seems when using grouping, all methods run are ordered per group and do not 
respect which class they are in.

Original issue reported on code.google.com by [email protected] on 4 Jun 2013 at 2:08