macrotest
Similar to [trybuild], but allows you to write tests on how macros are expanded.
A minimal macrotest setup looks like this:
In project's Cargo.toml:
toml
[dev-dependencies]
macrotest = "0.1"
Under project's tests/ directory create tests.rs:
```rust
pub fn pass() { let t = macrotest::TestCases::new(); t.pass("tests/expand/*.rs"); } ```
The test can be run with cargo test. It will individually extract each of
the source files matches the glob pattern as main.rs in a separate cargo crate in
temporary folder and will invoke cargo expand to expand macro invocations.
Project's crate will be listed under [dependencies] section of temporary crates and will be available
from the test cases.
Expansion result is compared with the corresponding .expanded.rs file (same file name as
the test except with a different extension). If file doesn't exists, it will create a new one
(this is how you update your tests).
Possible test outcomes are:
- Pass: expansion succeeded and a result is the same as in .expanded.rs file
- Fail: expansion is different from the .expanded.rs file content. This will print a diff
- Refresh: .expanded.rs didn't exist and has been created
NB: after execution of each test, a temporary folder with the crate is removed automatically.
First of all, a cargo-expand tool must be present.
You can install it with cargo:
bash
cargo install cargo-expand
A nightly compiler is required for this tool to operate, so it must be installed as well.
Inside your crate that provides procedural or declarative macros, create a test case
under tests directory.
Under the tests directory create an expand directory and populate it with
different expansion test cases as Rust source files.
Then, under the tests directory, create tests.rs file that will run the tests:
```rust
pub fn pass() { let t = macrotest::TestCases::new(); t.pass("tests/expand/*.rs"); } ```
And then you can run cargo test to
.expanded.rs files for each of the test cases under
the expand directory.expanded.rs files.expanded.rsJust remove the .expanded.rs files and re-run the corresponding tests. Files will be created
automatically; hand-writing them is not recommended.