You should use the Morse code they gave you:

The Morse code table is preloaded for you as a dictionary, feel free to use it:

Coffeescript/C++/Go/JavaScript/Julia/PHP/Python/Ruby/TypeScript: MORSE_CODE['.--']
C#: MorseCode.Get(".--") (returns string)
F#: MorseCode.get ".--" (returns string)
Elixir: @morse_codes variable (from use MorseCode.Constants). Ignore the unused variable warning for morse_codes because it's no longer used and kept only for old solutions.
Elm: MorseCodes.get : Dict String String
Haskell: morseCodes ! ".--" (Codes are in a Map String String)
Java: MorseCode.get(".--")
Kotlin: MorseCode[".--"] ?: "" or MorseCode.getOrDefault(".--", "")
Racket: morse-code (a hash table)
Rust: MORSE_CODE
Scala: morseCodes(".--")
Swift: MorseCode[".--"] ?? "" or MorseCode[".--", default: ""]
C: provides parallel arrays, i.e. morse[2] == "-.-" for ascii[2] == "C"
NASM: a table of pointers to the morsecodes, and a corresponding list of ascii symbols
All the test strings would contain valid Morse code, so you may skip checking for errors and exceptions. In C#, tests will fail if the solution code throws an exception, please keep that in mind. This is mostly because otherwise the engine would simply ignore the tests, resulting in a "valid" solution.