An utility for testing a function that takes in a string and returns a string.

How it works

The trycall macro takes in a path to a directory. The directory should contain two files for each test case:

• source - The source file with extension .txt
• expected - The expected output file with extension .out

The trycall macro will then run the function on each source file and compare the output to the expected file.

The below example will run the add_one function on each source file in the tests/add_one directory (relative to the crate's root) and compare the output to the respective expected file (e.g. tests/add_one/word.txt will be compared to tests/add_one/word.out).

• If the output does not match the expected file, the test will fail.
• If the expected file does not exist, it will be treated as an empty string.
• If the function panics, the test will fail.

Example

pub fn add_one(s: &str) -> String {
    s.parse::<i32>()
        .map(|n| (n + 1).to_string())
        .unwrap()
}

#[cfg(test)]
mod tests {
    #[test]
    fn add_one() {
        trycall::trycall!("tests/add_one").with(super::add_one);
    }
}

Updating the expected output

If you want to update the expected output, you can pass in the UPDATE_EXPECT environment variable. For example:

UPDATE_EXPECT=1 cargo test

Filtering

You can filter the test cases by passing in the trycall= prefix followed by a string which will be checked against the source file name. For example, if you want to run the test on the negative_number test case, you can run any of the following commands:

cargo test -- trycall=negative_number
cargo test -- trycall=negative
cargo test -- trycall=number

You can also pass in the test case source file path directly to the trycall macro:

#[test]
fn add_one() {
   trycall::trycall!("tests/add_one/negative_number.txt").with(super::add_one);
}