Question

I’m working on a laboratory practical with unit-testing, and below is a piece of code from the application that i’m testing. Most of the unit-testings are finished, but regarding the constructor below I just can’t figure out how to test it. For example, what exactly is the constructor doing with the array elements? What would be a good way of testing the construtor?

Is there maybe a kind soul out there who could give me a kick in the right direction?

  public struct Point { 
    public int x, y;

    public Point(int a, int b) {
      x = a;
      y = b;
    }
  }

…

  public Triangle(Point[] s) {
    sides = new double[s.Length];
    sides[0] = Math.Sqrt(Math.Pow((double)(s[1].x - s[0].x), 2.0) + Math.Pow((double)(s[1].y - s[0].y), 2.0));
    sides[1] = Math.Sqrt(Math.Pow((double)(s[1].x - s[2].x), 2.0) + Math.Pow((double)(s[1].x - s[2].x), 2.0));
    sides[2] = Math.Sqrt(Math.Pow((double)(s[2].x - s[0].x), 2.0) + Math.Pow((double)(s[2].x - s[0].x), 2.0));
  }

…

        [TestMethod()]
        public void TriangleConstructorTest1()
        {
            Point[] s = null; // TODO: Initialize to an appropriate value
            Triangle target = new Triangle(s);
            Assert.Inconclusive("TODO: Implement code to verify target");
        }

Answer 1

You are talking about the Traingle-constructor, aren’t you?

It looks like it is using the Pythagorean theorem to calculate the length of the triangle sides.
So you should test whether this calculation is done correctly.

In addition, you could check if the constructor detects invalid arguments, e.g.:

[TestMethod]
[ExpectedException(typeof(ArgumentNullException))]
public void Cannot_Create_Passing_Null()
{
   new Triangle(null);
}
[TestMethod]
[ExpectedException(typeof(ArgumentException))]
public void Cannot_With_Less_Than_Three_Points()
{
   new Triangle(new[] { new Point(0, 0), new Point(1, 1) });
}
[TestMethod]
[ExpectedException(typeof(ArgumentException))]
public void Cannot_Create_With_More_Than_Three_Points()
{
   new Triangle(new[] { new Point(0, 0), new Point(1, 1), new Point(2, 2), new Point(3, 3) });
}
[TestMethod]
[ExpectedException(typeof(ArgumentException))]
public void Cannot_Create_With_Two_Identical_Points()
{
   new Triangle(new[] { new Point(0, 0), new Point(0, 0), new Point(1, 1) });
}
[TestMethod]
[ExpectedException(typeof(ArgumentException))]
public void Cannot_Create_With_Empty_Array()
{
   new Triangle(new Point[] { });
}