As peer commenters have noted, coding agent can be really good at improving test coverage when needed.
But also as a slightly deeper observation - agentic coding tools really do benefit significantly from good test coverage. Tests are a way to “box in” the agent and allow it to check its work regularly. While they aren’t necessary for these tools to work, they can enable coding agents to accomplish a lot more on your behalf.
In my experience they write a lot of pointless tests that technically increase coverage while not actually adding much more value than a good type system/compiler would.
They also have a tendency to suppress errors instead of fixing them, especially when the right thing to do is throw an error on some edge case.
In my experience it works well even without good testing, at least for greenfield projects. It just works best if there are already tests when creating updates and patches.
As peer commenters have noted, coding agent can be really good at improving test coverage when needed.
But also as a slightly deeper observation - agentic coding tools really do benefit significantly from good test coverage. Tests are a way to “box in” the agent and allow it to check its work regularly. While they aren’t necessary for these tools to work, they can enable coding agents to accomplish a lot more on your behalf.
(I work on Copilot coding agent)
In my experience they write a lot of pointless tests that technically increase coverage while not actually adding much more value than a good type system/compiler would.
They also have a tendency to suppress errors instead of fixing them, especially when the right thing to do is throw an error on some edge case.
You can tell the AI not to suppress errors
In my experience it works well even without good testing, at least for greenfield projects. It just works best if there are already tests when creating updates and patches.
Have it write tests for everything and then you've got a well tested codebase.
Caveat empor, I've seen some LLMs mock the living hell out of everything, to the point of not testing much of anything. Something to be aware of.
I've seen too many human operators do that too. Definitely a problem to watch out for
You forgot the /s