How do I ensure a mock function is called exactly once?

The skill demonstrates how to use the .times(1) expectation on your mock objects to enforce strict call counting during test execution.

Does this support custom argument matching logic?

Yes, it provides guidance on using predicates, including the ability to pass custom closures to validate that function arguments meet specific criteria.

Can I mock async functions with this skill?

Yes, it includes specific implementation patterns for mocking asynchronous traits, which is essential for modern Rust applications using runtimes like Tokio.

What library does this skill use for mocking in Rust?

This skill focuses on using 'mockall', the most popular and feature-complete mocking library for the Rust programming language.

Is trait-based design required for this mocking approach?

While mockall can mock some concrete types, the best practice encouraged by this skill is using trait-based abstractions to decouple your code for maximum testability.

Rust Mocking & Unit Testing

Name: Rust Mocking & Unit Testing
Author: gar-ai

bygar-ai

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セキュリティとテスト

Simplifies Rust unit testing by generating mock implementations for traits and external dependencies using the mockall crate.

概要

This skill enables Claude to architect highly testable Rust applications through trait-based abstractions and the mockall framework. It provides comprehensive patterns for setting up mock expectations, handling asynchronous traits, and verifying complex interaction sequences. By guiding developers to isolate business logic from external side effects like databases or APIs, this skill helps create robust, isolated unit tests that run quickly and reliably without requiring live infrastructure.

主な機能

Advanced argument matching using predicates like eq, range, and custom functions
1 GitHub stars
Automatic mock generation using the #[automock] attribute
Support for mocking asynchronous traits with async-trait compatibility
Strict call counting and verification to ensure expected code paths are executed
Sequence enforcement for validating the order of operations in complex workflows

ユースケース

Simulating network failures and edge-case error returns in a controlled environment
Isolating business logic from database repositories or external API clients
Testing generic components by mocking traits with specific type parameters

概要

主な機能

Advanced argument matching using predicates like eq, range, and custom functions
1 GitHub stars
Automatic mock generation using the #[automock] attribute
Support for mocking asynchronous traits with async-trait compatibility
Strict call counting and verification to ensure expected code paths are executed
Sequence enforcement for validating the order of operations in complex workflows

ユースケース

Simulating network failures and edge-case error returns in a controlled environment
Isolating business logic from database repositories or external API clients
Testing generic components by mocking traits with specific type parameters