The test command

When writing a book, you sometimes need to automate some tests. For example, The Rust Programming Book uses a lot of code examples that could get outdated. Therefore it is very important for them to be able to automatically test these code examples.

mdBook supports a test command that will run all available tests in a book. At the moment, only Rust tests are supported.

Disable tests on a code block

rustdoc doesn’t test code blocks which contain the ignore attribute:

```rust,ignore
fn main() {}
```

rustdoc also doesn’t test code blocks which specify a language other than Rust:

```markdown
**Foo**: _bar_
```

rustdoc does test code blocks which have no language specified:

```
This is going to cause an error!
```

Specify a directory

The test command can take a directory as an argument to use as the book’s root instead of the current working directory.

mdbook test path/to/book

--library-path

The --library-path (-L) option allows you to add directories to the library search path used by rustdoc when it builds and tests the examples. Multiple directories can be specified with multiple options (-L foo -L bar) or with a comma-delimited list (-L foo,bar). The path should point to the Cargo build cache deps directory that contains the build output of your project. For example, if your Rust project’s book is in a directory named my-book, the following command would include the crate’s dependencies when running test:

mdbook test my-book -L target/debug/deps/

See the rustdoc command-line documentation for more information.

--chapter

The --chapter (-c) option allows you to test a specific chapter of the book using the chapter name or the relative path to the chapter.