Ensuring mobile app accessibility is essential for inclusive user experiences and compliance with standards such as the WCAG 2.2. However, many developers lack familiarity with accessibility guidelines, and automated testing or developer-authored test suites often fail to detect critical issues. This paper presents luisa, a framework for mutation testing that deliberately introduces accessibility issues into SwiftUI codebases. luisa automatically modifies interface components to remove or alter accessibility features, generating mutants that simulate common violations of WCAG 2.2 principles. These mutants enable developers to assess the fault-detection capability of accessibility testing tools and test suites, while also serving as educational examples for understanding the impact of poor accessibility practices. We define and implement 12 accessibility mutation operators derived from WCAG success criteria and evaluate them on open-source iOS applications. Results show that luisa effectively introduces realistic accessibility defects that are often missed by existing automated tools, demonstrating its potential to improve accessibility testing practices in iOS development.