Improving the reliability, quality, and maintainability of bioinformatics pipelines with nf-test.

BACKGROUND: The workflow management system Nextflow, together with the nf-core community, has established an essential ecosystem in bioinformatics. However, ensuring the correctness and reliability of large and complex Nextflow pipelines remains challenging due to the lack of a unified, automated unit-testing framework. RESULTS: To address this gap, we present nf-test, a modular testing framework for bioinformatics workflows. It enables users to test process blocks, workflow patterns, and entire pipelines in isolation while validating their outputs. Built with a syntax similar to Nextflow DSL2, nf-test offers unique features such as snapshot testing and smart testing, which optimize resource usage by testing only modified modules. We demonstrate across multiple pipelines that these features minimize development time, reduce test execution time by up to 80%, and enhance software quality by identifying bugs and issues early in the development process. CONCLUSIONS: Already adopted by numerous pipelines, nf-test significantly improves the robustness, maintainability, and reliability of bioinformatics pipelines.