Lib.rs

Expect Tests

Expect Tests is a Rust crate inspired by rust-analyzer's expect-test. Explanation can be found here.

Basic Usage:

expect!(fibonacci(15), "610");

The macro uses the Debug trait representation (except for string literals) and compares it to the provided string literal. In case of a mismatch, an error with a 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 the `run` feature of rust-analyzer.

Expect:
----
987
----

Actual:
----
610
----

Diff:
----
987610
----

If the UPDATE_EXPECT environment variable is set, the macro will directly update the source file to fix it. For 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:

Testing callbacks can be cumbersome because you'd need to collect into a vec. Here's an alternative using expect!:

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, a loop like the following will pass even though "2", "3", and "4" are never run:

for i in 0..2 {
  expect!(i, "0", "1", "2", "3", "4");
}

Expect Tokens:

Testing proc macros is now easier with expect tokens:

#[test]
fn test_enum() {
    let output = quote! {
        enum TrafficLight {
            Red,
            Yellow,
            Green
        }
    };
    expect_tokens!(
        output,
        r#"
        enum TrafficLight {
            Red,
            Yellow,
            Green,
        }
        "#
    );
}

Examples:

Check out the examples used to test this crate.

Alternatives:

• expect-test
• insta
• k9

Other Notes:

• Makes 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 to make the code look nicer.