Spock unit tests with ant build - ant

Question

I'm writing a unit test with Spock. I want to check all elements of an array using the spock
when: then:
block. I found the syntax here from the accepted answer. and based on that I wrote something like this -
then:
myArray.every { (it >= 0) && (it < 10) }
This works correctly with IntelliJ but when I build the test using Ant, it fails.
Ant and groovy setup - taken from here. I could see it working for simple conditions like myArray.length == 8.
Groovy version - 2.4.5
Spock version - spock-core-1.0-groovy-2.4.jar
JDK 1.8
Ant 1.9.6
Error -
[junit] Testcase: initializationError took 0 sec
[junit] Caused an ERROR
[junit] Test class should have exactly one public zero-argument constructor
[junit] java.lang.Exception: Test class should have exactly one public zero-argument constructor
[junit] at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
[junit]
[junit] Testcase: initializationError took 0 sec
[junit] Caused an ERROR
[junit] No runnable methods
[junit] java.lang.Exception: No runnable methods
[junit] at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
[junit]
[junit] Test package.MyTest$__spock_feature_0_0_closure1 FAILED
On looking at the class file created by the ant build, I see
public void $spock_feature_0_0(Object obj){
...
...
class __spock_feature_0_0_closure1 extends Closure implements GeneratedClosure {
}
...
...
new __spock_feature_0_0_closure1()
}
So looks like the closure is not accessible using Reflection!! Any thoughts?
Is my ant groovy configuration messed up(as I said earlier, simpler tests are working for me, so i hope not!)?, or am i just expecting too much from Spock.
An example of the scenario -
public class SpockTest extends Specification{
public def "example"(){
given:
int[] arr = new int[5];
when:
arr[0] = 1;
then:
arr.every { (it >= 0) }
}
}
Below junit also fails to run with the same error-
public class TestClass {
public int test1() {
class testInner {//local class
int a = 100;
public int getA() {
return a;
}
}
return new testInner().getA();
}
#Test
public void test2() {
System.out.println(test1());
assert 100 == test1();
}
}
UPDATE(29-Feb-16) - With the discussions so far, it seems like the problem is with Ant. Only the junit and groovy/Spock tests using/compiling to local classes are giving errors. Simpler cases are working fine.