Comparing Collection.Contains for various sets of data

Test-Collection-Contains.linq.cs

void Main()
{
	// https://stackoverflow.com/questions/150750/hashset-vs-list-performance/13089134?noredirect=1#comment76605526_13089134
	
	test(10, 5, 10, true);
	test(20);
	test(50);
	test(100);
	test(1000);
	
	test(10, 50, 10, true);
	test(1000, 50);
	
}

// Define other methods and classes here
static Random r = new Random();
string getRandomString(int size) {
	var sb = new StringBuilder();
	for(int i = 0; i < size; i++) sb.Append( (char)('a' + r.Next(0, 25)));
	return sb.ToString();
}

ICollection<string> createTestList<T>(int setSize, int minWordLength = 5, int wordLengthVariance = 10, int previewSize = 0) where T : ICollection<string>, new() {
	var set = new T();
	for(int i = 0; i < setSize; i++) set.Add(getRandomString(r.Next(minWordLength, minWordLength + wordLengthVariance)));
	
	if(previewSize > 0) set.Take(previewSize).Dump(string.Format("Test size {0} sample {1}", setSize, previewSize));
	
	return set;
}

List<T> getSearchKeys<T>(ICollection<T> set) {
	return _getSearchKeys(set).ToList();
}
IEnumerable<T> _getSearchKeys<T>(ICollection<T> set) {
	// first
	yield return set.First();
	
	// early
	yield return set.ElementAt(set.Count / 10);
	
	// middle
	yield return set.ElementAt(set.Count / 2);
	
	// late
	yield return set.ElementAt(set.Count / 10 * 9 - 1);
	
	// last
	yield return set.Last();	
}

void test(int setSize, int minWordLength = 5, int wordLengthVariance = 10, bool preview = false) {
	var list = createTestList<List<string>>(setSize, minWordLength, wordLengthVariance);
	var hashset = new HashSet<string>(list);
	
	var keys = getSearchKeys(list);
	
	if(preview) {
		list.Dump("Set");
		keys.Dump("Find");
	}
	
	// the thing that runs each test 10k times and prints the results, see https://gist.github.com/zaus/8055941
	new Perf {
		{ "list, first", n => list.Contains(keys[0]) },
		{ "hashset, first", n => hashset.Contains(keys[0]) },

		{ "list, early", n => list.Contains(keys[1]) },
		{ "hashset, early", n => hashset.Contains(keys[1]) },

		{ "list, middle", n => list.Contains(keys[2]) },
		{ "hashset, middle", n => hashset.Contains(keys[2]) },

		{ "list, late", n => list.Contains(keys[3]) },
		{ "hashset, late", n => hashset.Contains(keys[3]) },

		{ "list, last", n => list.Contains(keys[4]) },
		{ "hashset, last", n => hashset.Contains(keys[4]) },
	}.Vs(string.Format("Comparing set size {0} min word size {1}-{2}", setSize, minWordLength, minWordLength+wordLengthVariance));
}