public void Index()
{
SubString test = new SubString();
string source = "hello world are you ok the brown fox jumps over the lazy dog";
string pattern1 = "hello";
string pattern2 = "ok";
string pattern3 = "fox";
string pattern4 = "lazy";
string pattern5 = "dog";
Assert.AreEqual(0, test.Index(source, pattern1));
Assert.AreEqual(20, test.Index(source, pattern2));
Assert.AreEqual(33, test.Index(source, pattern3));
Assert.AreEqual(52, test.Index(source, pattern4));
Assert.AreEqual(57, test.Index(source, pattern5));
}