Expect Tests
Based on https://github.com/rust-analyzer/expect-test Explanation: https://blog.janestreet.com/the-joy-of-expect-tests/
Basic Usage:
expect!(fibonacci(15), "610");
The macro will use the Debug trait representation (except for string literals) and compare it to the string literal.
If there is a mismatch such as expect!(fibonacci(15), "987");, an error with the diff will be shown:
You can update all `expect!` tests by running:
UPDATE_EXPECT=1 cargo test
To update a single test, place the cursor on `expect` token and use `run` feature of rust-analyzer.
Expect:
----
987
----
Actual:
----
610
----
Diff:
----
987610
----
If UPDATE_EXPECT environment variable is set, the macro will directly update the source file to fix it. Here's an example:
expect!(fibonacci(15));
After running UPDATE_EXPECT=1 cargo test, your source file should automatically be updated to
expect!(fibonacci(15), "610");
Multiple expects:
Maybe you want to test a callback, but for some reason (maybe due to laziness) it is too cumbersome to collect it into a vec before expect!ing it. We can do something like this:
fn some_complicated_io_func(callback: impl Fn(i32)) {
callback(5);
callback(3);
callback(10);
}
some_complicated_io_func(|status_value| {
expect!(status_value, "5", "3", "10");
})
Caveat: expect-tests cannot detect when the expect! macro is never called. Therefore, something like
for i in 0..2 {
expect!(i, "0", "1", "2", "3", "4");
}
will pass even though "2", "3", and "4" are never run.
Examples (that are used to test this crate!): https://github.com/awesomelemonade/expect-tests/blob/master/src/tests.rs
Alternatives:
expect-test: https://docs.rs/expect-test/latest/expect_test/ insta: https://crates.io/crates/insta k9: https://crates.io/crates/k9
Other notes:
- Does a "best effort" to comply with rustfmt. When the macro detects a multiline expect, updating will attempt to insert newlines where appropriate
- Indentations are ignored in the string literals when comparing. This is so it is prettier in the code.