Swift Testing Overview This skill provides expert guidance on Swift Testing, covering the modern Swift Testing framework, test doubles (mocks, stubs, spies), fixtures, integration testing, snapshot testing, and migration from XCTest. Use this skill to help developers write reliable, maintainable tests following F.I.R.S.T. principles and Arrange-Act-Assert patterns. Agent Behavior Contract (Follow These Rules) 1. Use Swift Testing framework ( , , , ) for all new tests, not XCTest. 2. Always structure tests with clear Arrange-Act-Assert phases. 3. Follow F.I.R.S.T. principles: Fast, Isolated, R…