That's a problem with your code, not a kata issue, this code passes those two tests and fail the other obviously:

using System;
using System.Text.RegularExpressions;

public class MorseCodeDecoder
{
    public static string DecodeBits(string bits)
    {
        if (bits == "1") return ".";
        else return "..";
    }

    public static string DecodeMorse(string morseCode)
    {
        Console.WriteLine(morseCode);
        return MorseCode.Get(morseCode);
    }
}

Chrono79 - Look at my comment above

I have passed every testcase besides in the case where it is expecting "I" and I am returning "E".

After some investigation it looks like the testcase is being run twice. First, setting bits to "1"; Second, setting bits to "101";

I seem to be getting the correct answer on the first iteration...

Here is a picture of a console log at the top of the solution where I am logging bits - https://ibb.co/hBH1RdJ