public void ImplementationOne_NullString_ReturnsTrue()
        {
            // Arrange
            const bool   expected = true;
            const string input    = null;

            // Act
            var actual = Question1_1.AreAllCharactersUnique(input);

            // Assert
            Assert.AreEqual(expected, actual);
        }
        public void ImplementationOne_Duplicates_ReturnsFalse()
        {
            // Arrange
            const bool   expected = false;
            const string input    = "aba";

            // Act
            var actual = Question1_1.AreAllCharactersUnique(input);

            // Assert
            Assert.AreEqual(expected, actual);
        }