mdBook/tests/testsuite/README.md

Testsuite

Introduction

This is the main testsuite for exercising all functionality of mdBook.

Tests should be organized into modules based around major features. Tests should use BookTest to drive the test. BookTest will set up a temp directory, and provides a variety of methods to help create a build books.

Basic structure of a test

Using BookTest, you typically use it to copy a directory into a temp directory, and then run mdbook commands in that temp directory. You can run the mdbook executable, or use the mdbook API to perform whatever tasks you need. Running the executable has the benefit of being able to validate the console output.

See build::basic_build for a simple test example. I recommend reviewing the methods on BookTest to learn more, and reviewing some of the existing tests to get a feel for how they are structured.

For example, let's say you are creating a new theme test. In the testsuite/theme directory, create a new directory with the book source that you want to exercise. At a minimum, this needs a src/SUMMARY.md, but often you'll also want book.toml. Then, in testsuite/theme.rs, add a test with BookTest::from_dir("theme/mytest"), and then use the methods to perform whatever actions you want.

BookTest is designed to be able to chain a series of actions. For example, you can do something like:

BookTest::from_dir("theme/mytest")
    .build()
    .check_main_file("book/index.html", str![["file contents"]])
    .change_file("src/index.md", "new contents")
    .build()
    .check_main_file("book/index.html", str![["new contents"]]);

Snapbox

The testsuite uses snapbox to drive most of the tests. This library provides the ability to compare strings using a variety of methods. These strings are written in the source code using either the str! or file! macros.

The magic is that you can set the SNAPSHOTS=overwrite environment variable, and snapbox will automatically update the strings contents of str!, or the file contents of file!. This makes it easier to update tests. Snapbox provides nice diffing output, and quite a few other features.

Expected contents can have wildcards like ... (matches any lines) or [..] (matches any characters on a line). See snapbox filters for more info and other filters.

Typically when writing a test, I'll just start with an empty str! or file!, and let snapbox fill it in. Then I review the contents to make sure they are what I expect.

Note that there is some normalization applied to the strings. See book_test::assert for how some of these normalizations happen.