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    I religiously unit test most of my code but I have found unit testing exploratory, scientific code less than useless. The methodology fundamentally doesn’t seem to work here. I don’t know any computational scientist in my field who unit-tests their analysis code. I’m not sure what the reason for this mismatch is but one of the reasons is certainly that, except for trivial units, it’s hard or impossible to establish good test cases. Commented Jul 6, 2018 at 11:30
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    @KonradRudolph the trick in those cases is likely to be clean separation of concerns between parts of your code that have clearly definable behaviour (read this input, compute this value) from the parts of your code that are either genuinely exploratory or are adapting to e.g. some human-readable output or visualisation. The problem here is likely to be that poor separation of concerns leads to blurring those lines, which leads to a perception that unit testing in this context is impossible, which leads you back to the start in a repeating cycle. Commented Jul 6, 2018 at 12:19
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    On a side note, version control also works quite nicely for LaTeX documents, since the format is amenable to text diffing. In this way, you can have a repository for both your papers and the code that supports them. I suggest looking into distributed version control, like Git. There's a bit of a learning curve, but once you understand it, you've got a nice clean way to iterate on your development and you have some interesting options to use a platform like Github, which offers free team accounts for academics. Commented Jul 6, 2018 at 13:20
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    @AntP It's possible that there just isn't that much code that can be meaningfully refactored out into well-defined testable units. A lot of scientific code is essentially taping a bunch of libraries together. These libraries will already be well tested and cleanly structured, meaning the author only has to write "glue", and in my experience, it's damn near impossible to write unit tests for glue that aren't tautological. Commented Jul 6, 2018 at 15:54
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    "Between version control and writing unit tests as you go, you code will naturally become a lot cleaner." This is not true. I can attest to it personally. Neither of these tools stops you from writing crappy code, and in particular, writing crappy tests on top of crappy code just makes it even harder to clean up. Tests are not a magic silver bullet, and talking like they are is a terrible thing to do to any developer still learning (which is everyone). Version control generally never causes damage to the code itself like bad testing does, though. Commented Jul 6, 2018 at 19:01