Short explanation of the title: imagine you have a legacy mudball codebase in which most service methods are usually querying the database (through EF), modifying some data and then saving it in at the end of the method.
This code is hard to debug, impossible to write unit tests for and generally performs badly because developers often make unoptimized or redundant db hits in these methods.
What I've started doing is to often make all the data loads before the method call, put it in a generic cache class (it's mostly dictionaries internally), and then use that as a parameter or a member variable for the method - everything in the method then gets or saves the data to that cache, its not allowed to do db hits on its own anymore.
I can now also unit test this code as long as I manually fill the cache with test data beforehand. I just need to make sure that i actually preload everything in advance (which is not always possible) so I have it ready when I need it in the method.
Is this good practice? Is there a name for it, whether it's a pattern or an anti-pattern? I'm tempted to say that this is just a janky repository pattern but it seems different since it's more about how you time and cache data loads for that method individually, rather than overall implementation of data access across the app.
In either case, I'd like to learn either how to improve it, or how to replace it.
I'm not sure how you do it at the moment or already know this since you mention repository pattern. But here's how I know.
A pattern I encountered at my workplace is a split between the repository and the data access (Dao) layer.
The repository implements an interface which other parts of your program uses to get data. The repository askes the data access layer to make database calls.
For testing other parts of the programs, we mock the repository interface, and implement simple returns of data instead of relying on the database at all. Then we have full control of what goes in and out of your legacy code, assuming you are able to use this.
For testing the dao, I don't actually have much experience since that's not a good option for us at the moment, but as others mentioned you can use in memory databases or manually mock the connection object provided to the dao to test that your save methods store the correct data. The latter being somewhat clunky in my experience but the best option when you are trying to save something with 20 values and making sure they end up in the right order or have the right values when converting enum values to strings for example.
I don't know much about cache, but if you want to keep it then it's possible to do it in the repository class.