public void Predecessor_ValidInput_ReturnsCorrectPostalCode(string postalCode, string postalCodePredecessor)
 {
     var code = new LIPostalCode(postalCode);
     var codePredecessor = new LIPostalCode(postalCodePredecessor);
     Assert.AreEqual(codePredecessor, code.Predecessor);
     Assert.AreEqual(codePredecessor.ToString(), code.Predecessor.ToString());
     Assert.AreEqual(codePredecessor.ToHumanReadableString(), code.Predecessor.ToHumanReadableString());
 }
 public void AreAdjacent_WithAdjacentPostalCodes_ReturnsTrue(string code)
 {
     var x = new LIPostalCode(code);
     var xPred = x.Predecessor;
     var xSucc = x.Successor;
     Assert.IsTrue(PostalCode.AreAdjacent(x, xPred));
     Assert.IsTrue(PostalCode.AreAdjacent(xPred, x));
     Assert.IsTrue(PostalCode.AreAdjacent(x, xSucc));
     Assert.IsTrue(PostalCode.AreAdjacent(xSucc, x));
     Assert.IsFalse(PostalCode.AreAdjacent(xPred, xSucc));
 }             
 public void GetHashCode_WithEqualObject_EqualHashes(string code)
 {
     var x = new LIPostalCode(code);
     var y = new LIPostalCode(code);
     Assert.IsTrue(x.GetHashCode() == y.GetHashCode());
 }