Category: rust

  • Testing in Rust: Writing to Stdout [rust, testing]

    For the last two years, I’ve been one of the organizers of an elective Rust course in Sofia University. Last semester, one of the homework assignments we came up with was to build several kinds of “logger” structs with buffering, multiple outputs, and with tagged logging. (The full assignment is here, but all the instructions are in Bulgarian.)

    It was a pretty good exercise on using Rc and RefCell that wasn’t a linked list or a similar data structure. The goal was to ensure a logger can be cloned, with the copies sharing both the same buffer and output.

    Testing the code seemed easy at first glance, but I did run into a bit of a problem when simulating loggers printing to “the screen”. The solution is not exactly complicated, but I think it’s a good pattern to share.

  • Testing in Rust: Temporary Files [rust, testing]

    I recently wrote a tool to manipulate images embedded in mp3 tags: id3-image. To be able to make changes to the code with confidence, I needed tests. Rust comes with the very sensible Write trait that could have allowed me to mock any IO (a blog post for another day), but in this case, the project relied on the excellent id3 crate, so I wasn’t doing any file-writing myself.

    Instead, I wanted to have an actual mp3 file and an actual image, apply my code to them, and inspect the results. This generally isn’t difficult to do, but I ran into a few unexpected gotchas, so I’ll summarize how I ended up implementing it.