Yes, your saltwater tests will work in freshwater. These test for specific things. For example any test for pH is measuring hydrogen icons whether those are in freshwater, saltwater, beer, pee, etc..., even soil if you know how to prepare the sample. Same for ammonia, nitrite, nitrogen, KH, GH and even salt. There can be issues at the limits like measuring really low pH, but that's true for all kinds of tests. How good a test result is has a great deal to do with the user.
Some people add salt to their freshwater pond and there is no adjustment needed for standard pond/aquarium type tests.
For sure you want to be careful about what the test kits says to do given a certain level. For example, if you tested for salt (I don't know what tests you have) and got a low number your test kit might recommend adding a lot of salt because it assumes you want saltwater.
The best test kit you have is your brain. I've seen so many people in forums use test kits to do horrible things to their pond. It can be very hard to watch.
For example, imo a pond owner wanting to test water should know how ammonia and ammonium work and how they relate to temperature and pH level. It's not really very complicated but rarely discussed. Instead if someone posts a high Total Ammonia level they're told to do immediate water changes which for an inexperienced owner can lead to dead or injured fish. Be very wary of online advice where everyone sounds like an expert.
