Detecting a call to a Java API method from source code

Question

Suppose that I want to write a unit test for a method or class that makes sure that the source code of that method does not call a certain Java API method (in this case, Arrays.sort ). Is this even possible? The reason for which I want this is because I want to come up with automatic tests that detect if Arrays.sort has been called from anywhere inside a particular method of a particular class, in which case I want to be failing the relevant test. Unfortunately, a text-based approach is purely unsatisfactory, because it would also catch potential references to Arrays.sort from within source code comments, for instance. Any help appreciated.

Answer 1

You can do it by creating your interface for sorting and an implementation that uses Arrays.sort

public interface SortUtil {}

public class SortUtilImpl implements SortUtil { 
  public void sort(Collection c) {
    Arrays.sort(c);
  }
}

Now you must use the interface in your 'client' class for sorting. For unit tests, replace the real implementation by a test mock one. like:

public SortUtilMock implements SortUtil {
  public void sort( Collection c) {
    StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
    //... here you check if the sort is called by a forbidden method
  }
}

Best regards, Zied