I just would like a to understand how mRNA works.
Is it like a trojan horse that transports another virus code to reprogram your cells? Is this the correct way to understand it?
If this is correct, what would unit tests and acceptance tests look like for this? Does it leave any technical debt in what it reprograms in your cells?
DNA is transcribed into mRNA. That mRNA then goes to a ribosome to be turned into proteins. The mRNA is the 'message' to other cellular machinery of how to make proteins.
This is the 'central dogma' of molecular biology: DNA > RNA > Protein.
The viral part is that some viruses will just be mRNA in a little molecular capsule. When the virus docks with a cell, it injects the mRNA. This free floating mRNA may get picked up by the cell and then turned into the proteins that it codes for. In the case of a virus, that will be proteins to make more viruses.
I'm unsure what you mean by a unit test in terms of biology. If you are asking if the ribosome complexes will check to see if some mRNA is a viral one, then no, they do not. These proteins are too small and chaotic to really have those kinds of things.
I'm also unsure of what you mean by tech debt here. The virus, once successfully copying itself, will almost always cause cell death and lysis.
To be clear, this process is very complicated and caveats abound to everything I've told you. But this is a HN comment section, not a full four year set of courses on virology.