Macro k9::assert_matches_snapshot

macro_rules! assert_matches_snapshot {
    ($to_snap:expr) => { ... };
    ($to_snap:expr, $description:expr) => { ... };
}

Formats passed value and asserts that it matches existing snaphot. If snapshot file for this test does not exist, test can be run with K9_UPDATE_SNAPSHOTS=1 environment variable to either create or replace existing snapshot file. Snapshots will be written into __k9_snapshots__ directory next to the test file.

#[test]
fn my_test() {
    struct A {
        name: &'a str,
        age: u32
    }

    let a = A { name: "Lance", age: 9 };

    // When first run with `K9_UPDATE_SNAPSHOTS=1` it will
    // create `__k9_snapshots__/my_test_file/my_test.snap` file
    // with contents being the serialized value of `a`.
    // Next time the test is run, if the newly serialized value of a
    // is different from the value of that snapshot file, the assertion
    // will fail.
    assert_matches_snapshot!(a);
}