public void EnumerableEqualityComparerGetHashCodeReturnsDefaultHashCodeIfSequenceIsEmpty()
{
const int expectedHashCode = 23;
var comparer = new EnumerableComparer <int>();
IEnumerable <int> sequence = new List <int>();
int result = comparer.GetHashCode(sequence);
Assert.AreEqual(expectedHashCode, result);
}
public void EnumerableEqualityComparerGetHashCodeReturnsZeroIfSequenceIsNull()
{
const int expectedHashCode = 0;
var comparer = new EnumerableComparer <int>();
IEnumerable <int> sequence = null;
int result = comparer.GetHashCode(sequence);
Assert.AreEqual(expectedHashCode, result);
}
public void EnumerableEqualityComparerGetHashCodeReturnsSameHashCodeIfSequenceContainsNullElements()
{
var comparer = new EnumerableComparer <int?>();
IEnumerable <int?> sequence = new List <int?> {
1, 2, null, 4, 5
};
//get the HashCode 2000 times to confirm it is consistent for lifetime of the enumerable
HashSet <int> hashes = new HashSet <int>();
for (int i = 0; i < 2000; i++)
{
hashes.Add(comparer.GetHashCode(sequence));
}
Assert.AreEqual(1, hashes.Count);
}