# Testing
We make use of UI tests, which compare the exact diagnostic output from a linter via `.errors` files. These files are
automatically generated, see [Updating outputs](#updating-outputs).
## Updating outputs
Once the diagnostic output looks correct, the `.errors` file(s) can be updated by setting the `BLESS` environment variable.
For example
```bash
BLESS=1 cargo test [TEST_NAME]
```
## Configured tests
If a directory contains a `config.toml` file, the linter will be run twice. Once with the new config and once with the default
config. The runs will generate `source.errors` and `source.errors.default` respectively.