TDD: A simple example

1_define_test.cs

// 1. Create a simple test method. 
// Example test harness calls:
// public static void AlgUtil_Harness() {
//	Test_CountTwos(232);
//	Test_CountTwos(-232);	
// }

private static void Test_CountTwos(int n) {

	Console.WriteLine("The number of twos in {0} are: {1}", n, AlgUtil.CountTwos(n));
}

2_intial_logic.cs

// 2. Create a skeleton method/function and test.

using System;

namespace Dsa
{
	public static class AlgUtil
	{
             // Counts the number of 2's in an integer.
             public static int CountTwos(int n) {
			
		return -1;
	     }
        }
}

2a_test1_result.txt

The number of twos in 232 are: -1
The number of twos in -232 are: -1

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3_completed_logic.cs

// 3. Complete implementation and retest. 

using System;

namespace Dsa
{
	public static class AlgUtil
	{
            // Counts the number of 2's in an integer.
            public static int CountTwos(int n) {
		// I don't want to handle negative numbers atm.
		// Note: We should use Code Contracts if using .NET 4.0
		if (n < 0) return -1;
			
		string number = n.ToString();
		int count = 0;
		for (int i = 0; i < number.Length; i++) {
			if (number[i] == '2') count++;
		}
			
		return count;
	    }
        }
}

3b_test2_result.txt

The number of twos in 232 are: 2
The number of twos in -232 are: -1

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