Argument capturing on the insides of closures in Spock - unit-testing

Question

I am trying to test a method that does an invocation with a closure, something like this:
def foo(Long param) {
AnObject.doSomething {
bar(param)
}
}
And I want to test that doSomething is called with a closure that calls bar with the expected value inside.
I'm able to test properly the doSomething invocation by creating a spy and doing
when:
service.foo(1L)
then:
1 * AnObject.doSomething{_}
However, I cannot seem to find a way to perform assertions on the contents of the closure.
What's the appropriate way to assert that inside the closure bar gets called with 1L?

Answer 1

Without seeing more of your code, I think you would need to spy on the class providing the bar method. This is a bit contrived because the test is supplying the closure, but I think it is something like this:
import spock.lang.Specification
class Bar {
void bar(def param) {
println param
}
}
class DoSomethingTestSpec extends Specification {
class AnObject {
void doSomething(Closure c) {
def param = 1L
c.call(param)
}
}
def "test AnObject doSomething calls the closure"() {
given:
def closure = { def p ->
Bar.bar(p)
}
and:
GroovySpy(Bar, global:true)
and:
AnObject anObject = new AnObject()
when:
anObject.doSomething(closure)
then:
1 * Bar.bar(_) >> { args ->
assert args[0] == 1L
}
}
}