public void RandomString_WithSpecificChars_ShouldReturnSpecificString()
        {
            // Arrange

            // Act

            string random = RandomString(50000, letters: "AB", numbers: "12", symbols: "!?");

            // Assert

            Assert.Equal(50000, random.Length);
            Assert.False(random.Any(c => RANDOM_LETTERS.Replace("AB", string.Empty).Contains(c)));
            Assert.False(random.Any(c => RANDOM_NUMBER.Replace("12", string.Empty).Contains(c)));
            Assert.False(random.Any(c => RANDOM_SYMBOLS.Replace("!?", string.Empty).Contains(c)));
        }