Craig Pardey

I attended a talk at the Toronto Agile Tour on Deliberate Practice that focused on TDD Games and other programming challenges like Kata.  Among the challenges were things like solving a problem without using the ‘if’ keyword, or without using primitives.

Solving simple problems using these challenges makes us better programmers because they force us to come up with multiple, creative solutions to the same problem.

Here’s my solution for how to divide without using the division operator (“/”) in Java. The method should take a numerator and a denominator and return the largest integer multiplier. For example 10/3 = 3, which would be called as int result = divide(10, 3)

public interface DivisionOperator {
  int divide(int numerator, int denominator);
}

/** ************************************* */
public class Division implements DivisionOperator {
  public int divide(int numerator, int denominator) {
    if( denominator == 0){
      throw new IllegalArgumentException("Denonimnator cannot be zero");
    }
    int i = 1;
    while( denominator * i <= numerator){
      i++;
    }
    return i - 1;
  }
}

/** ************************************* */
public class DivisionTest {
  @Test
  public void testDivision() {
    checkDivisionOperatorImplementation(new Division());
    checkDivisionOperatorImplementation(new DivisionAlternateAnswer());
  }

  private void checkDivisionOperatorImplementation( DivisionOperator div){
    try {
      div.divide(0, 0);
      Assert.fail("Expected divide by zero error");
    } catch (Exception e) {
      // Expected
    }
    Assert.assertEquals( 0, div.divide(0, 10));
    Assert.assertEquals( 3, div.divide(10, 3));
    Assert.assertEquals( 0, div.divide(3, 10));
    Assert.assertEquals( 1, div.divide(3, 3));
  }
}

I came up with a few implementations (hence the interface, makes testing much easier) but I think this one is the cleanest. I’m pretty sure there’s a solution using bit shifting but let’s face it, most developers don’t use bit shifting in their code.

It can be difficult to be Agile when working with 3rd party software framework.  The vendor product may dictate many aspects of the software architecture thwarting your attempts at automated testing and continuous build.

However there are steps you can take to make Agile easier.  I’ll discuss a few of the options that have worked for me on my current project.

• Insulate yourself from static methods.
• Introduce wrappers (Facades) to vendor classes.
• Introduce Spring, with different contexts for testing vs production, to allow easy substitution of vendor classes.
• Make use of mock objects for testing your code in isolation.
• If possible, move responsibility into services that live outside the framework.

In our particular case we’ve done all of the above and have managed to build a stable system with respectable test coverage.  We’ve also engaged the vendor to see if they can modify some of the framework interfaces to simplify unit testing, and they have been open to our suggestions.