public void Update_CaseWhenPair_ChangeThen ()
{
var caseWhenPair = new SqlCaseExpression.CaseWhenPair (_predicate1, _value1);
var result = caseWhenPair.Update (_predicate1, _value2);
Assert.That (result, Is.Not.SameAs (caseWhenPair));
Assert.That (result.When, Is.SameAs (_predicate1));
Assert.That (result.Then, Is.SameAs (_value2));
}