Provides cross-platform abstractions for Clojure, ClojureScript, ClojureCLR, and Babashka. Handles platform-specific differences in file I/O, exception handling, time formatting, and dynamic function invocation. Demonstrates skill in managing subtle platform variations while maintaining a clean, unified API.

A self-contained command-line argument parser supporting parameters, options, switches, and multi-values. Features automatic help text generation with proper formatting and wrapping, error handling for missing/unexpected arguments, and flexible option parsing. Shows expertise in CLI design with attention to usability details like help text alignment and line wrapping.

Implements the core component system for tests using Clojure protocols and types. Defines Descriptions (test suites), Characteristics (individual tests), hooks (before/after/around), and bindings (with/with-all). Demonstrates sophisticated use of Clojure's type system and protocols to create an extensible, hierarchical test structure.

A complete stubbing/mocking framework that records invocations, supports configurable return values and implementations, and provides rich argument matching (including special :* matcher and fn? predicates). Features verification macros like should-have-invoked with detailed failure messages. Shows skill in designing a usable mocking library with clear semantics.

Implements line-number based test filtering that resolves file:line targets to specific tests by walking the component tree and finding the best matching characteristic. Handles edge cases like Windows paths, missing files, and line numbers above/below test definitions. Demonstrates strong problem-solving for a specific testing workflow need.