Verifying non spy method calls with Spock - groovy

Question

I want to use spock to find if a method in a class was called. But when I try to verify it, the when block says that the method was never called.
public class Bill {
public Bill(Integer amount) {
this.amount = amount;
}
public void pay(PaymentMethod method) {
Integer finalAmount = amount + calculateTaxes();
method.debit(finalAmount);
}
private Integer calculateTaxes() {
return 0;
}
private final Integer amount;
}
public class PaymentMethod {
public void debit(Integer amount) {
// TODO
}
public void credit(Integer amount) {
// TODO
}
}
import spock.lang.Specification
import spock.lang.Subject
class BillSpec extends Specification {
#Subject
def bill = new Bill(100)
def "Test if charge calculated"() {
given:
PaymentMethod method = Mock()
when:
bill.pay(method)
then:
1 * method.debit(100)
// 1 * bill.calculateTaxes() // Fails with (0 invocations) error
0 * _
}
}
In the example above all I want to do is verify if calculateTaxes is being called but the test fails with (0 invocations). I tried using spy but am not sure what would be the syntax since Bill takes a parameterized constructor.

Answer 1

You can test calculateTaxes() call when you Spy the Bill instance like this:
class SpyTestSpec extends Specification {
def "Test if charge calculated"() {
given:
def bill = Spy(new Bill(100))
PaymentMethod method = Mock()
when:
bill.pay(method)
then:
1 * method.debit(100)
1 * bill.calculateTaxes()
1 * bill.pay(method)
0 * _
}
}
Another important thing is to make calculateTaxes() method visible for the test, otherwise it will still fail:
public Integer calculateTaxes() { ... }
Note that if you want to test that nothing else was called then you should also add:
1 * bill.pay(method)
And here is the result: