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I still struggle to understand the real benefit of unit tests; the most intuitive tests that test real business logic that I've written always become something

I still struggle to understand the real benefit of unit tests; the most intuitive tests that test real business logic that I've written always become something like semi-integration tests. Pure unit tests that test a small isolated function are almost never useful to catch bugs after they're written. The only legitimate use for them has been that it's easier to understand the purpose of the function and edge cases. At times it makes me think about edge cases and identify bugs WHIlE writing the tests, but once they're written, they're never useful unless someones actively trying to understand that exact unit of code.

gonzo41 7y ago
Depends on how you define a unit and what you're willing to mock. I treat a 'unit' as a piece of functionality. So one method on an API is a unit. if it does complex stuff then there may be more targeted tests down below. and depending on what sort of work it does i may not bother with unit tests because mocking a DB transaction isn't worth it. In java land when I'm writing stuff i use unit tests mostly as a place where i can run code without having to compile the whole app. And any tests that come out of it just end up being a bit of regression protection. But there's always a bigger slightly more complex unit test i write which tests the bigger unit of function. And those really straddle the line between unit and integration testing but i find i get the most value from them because one you lock in and publish functionality you have a contract you have to honor.
mixmastamyk 7y ago
The benefit is being able to make changes and sleep soundly at night. I agree with the grandparent that they are more useful as a project matures rather than the design stage. Starting small and adding tests as designs solidify is a good tradeoff.
asdfasdfasdfa 7y ago
You say you've never understood the benefit of unit tests but you list three really great things: they help you debug stuff while you're writing it, they help you understand what you're writing and the edge cases, and they help others understand your code later. That's all great stuff.
skybrian 7y ago
For unit testing, I suggest starting with parsers, or any string-parsing code you have. They tend to be nicely self-contained and have lots of edge cases that you can test in a data-driven way, using a loop. Even if you're just using a regular expression for parsing, it can be worth moving the parsing code to its own function and testing it like a parser.

gonzo41 7y ago

Depends on how you define a unit and what you're willing to mock. I treat a 'unit' as a piece of functionality. So one method on an API is a unit. if it does complex stuff then there may be more targeted tests down below. and depending on what sort of work it does i may not bother with unit tests because mocking a DB transaction isn't worth it. In java land when I'm writing stuff i use unit tests mostly as a place where i can run code without having to compile the whole app. And any tests that come out of it just end up being a bit of regression protection. But there's always a bigger slightly more complex unit test i write which tests the bigger unit of function. And those really straddle the line between unit and integration testing but i find i get the most value from them because one you lock in and publish functionality you have a contract you have to honor.

mixmastamyk 7y ago

The benefit is being able to make changes and sleep soundly at night. I agree with the grandparent that they are more useful as a project matures rather than the design stage. Starting small and adding tests as designs solidify is a good tradeoff.

asdfasdfasdfa 7y ago

You say you've never understood the benefit of unit tests but you list three really great things: they help you debug stuff while you're writing it, they help you understand what you're writing and the edge cases, and they help others understand your code later. That's all great stuff.

skybrian 7y ago

For unit testing, I suggest starting with parsers, or any string-parsing code you have. They tend to be nicely self-contained and have lots of edge cases that you can test in a data-driven way, using a loop. Even if you're just using a regular expression for parsing, it can be worth moving the parsing code to its own function and testing it like a parser.