I run tests with this command usually:

    ant -Drun.test.xmx=1g clean test

I get the following error:

 [testng] Exception in thread "main" java.lang.OutOfMemoryError: GC overhead limit exceeded
   [testng] at jdk.internal.org.objectweb.asm.ByteVector.enlarge(ByteVector.java:331)
   [testng] at jdk.internal.org.objectweb.asm.ByteVector.putUTF8(ByteVector.java:243)
   [testng] at jdk.internal.org.objectweb.asm.ClassWriter.newUTF8(ClassWriter.java:1089)
   [testng] at jdk.internal.org.objectweb.asm.ClassWriter.newNameTypeItem(ClassWriter.java:1559)
   [testng] at jdk.internal.org.objectweb.asm.ClassWriter.newNameType(ClassWriter.java:1542)
[...]

I think @fork tests should be passed with VM options specified in project.properties.