1 day, on-site or remote
Testing in Rust: going beyond the basics
No application is an island: you need to interact with third-party APIs, databases and who knows what else. Testing those interactions is tricky, to say the least! This workshop will focus on expanding your Rust testing toolkit, going beyond the basic techniques you're already familiar with. At the end of the session, you'll have a strategy to test most of the scenarios that are relevant for a complex Rust application.
The workshop is designed for software developers who have a good understanding of Rust's basic concepts and want to move beyond the built-in testing toolkit.
If you are new to Rust instead, you might be interested instead in our introductory testing workshop.
anchorWorkshop overview
What is a test?
We will take a look under the hood to understand how the Rust built-in testing framework works. Armed with this knowledge, we will explore the runtime implications of different approaches for test organisation. We will also cover alternative test runners, such as
cargo-nextest.Test isolation: filesystem
All tests in Rust share the same filesystem as the underlying host, a problematic situation when multiple tests want to interact with the "same" files or touch directories that could affect the behaviour of the system they are being executed from. We will explore various techniques to manage this scenario, including the
tempfilecrate.Test isolation: the database
The database is another shared resource that can cause problems when running tests in parallel. We will explore how to use Docker to run an isolated database instance for each test, and how to use the
sqlxcrate to manage the database lifecycle.Mocks, stubs and fakes
In order to isolate the behaviour of a system under test, it is not unusual to replace some of its dependencies with "fake" implementations. We will explore the different types of fakes and how to use them in Rust. We will review, in particular, the
mockallcrate and the testing implications of using generics and dynamic dispatch for polymorphism.HTTP mocking
It is undesirable to have tests that hit real HTTP endpoints from third-party APIs, for a variety of reasons. We will explore how to use the
wiremockcrate to shield our tests from the outside world and make assertions on the HTTP requests that are being sent.Snapshot testing
Snapshot testing is a technique that allows us to capture the output of a system under test and compare it with a previously saved version. It is quite useful when working with complex data that might change frequently, such as HTML or error messages. We will explore how to use the
instacrate to implement snapshot testing and manage the snapshots lifecycle.Executing logic before and after a test run
It is often desirable to execute the same logic before and after each test in our suite. We will explore a variety of techniques to achieve this, from a bespoke
#[test_case]procedural macro to a custom test harness (vialibtest_mimic).Black-box testing
We will combine everything we have learned so far into an easy-to-use setup that allows you to run black-box tests against a real database and a real HTTP server, without having to orchestrate multiple commands—just
cargo testand you are good to go!
