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Swift Testing vs XCTest
Swift Testing is Apple's modern framework, and the comparison with XCTest is a current, high-signal interview topic. Know both and why each exists.
How they differ
Swift Testing uses the @Test macro and #expect and #require expectations, with clearer failure diagnostics, built-in parameterized tests via arguments, tags, and better async and concurrency support. XCTest uses XCTestCase subclasses and XCTAssert functions and remains the incumbent, with mature UI testing and vast existing coverage across real codebases.
Which to use and how to answer
For new code, Swift Testing is the modern default and signals you are current, while XCTest is still everywhere and required for UI tests today, so you should know both. The senior answer is that they interoperate in the same target, so you adopt Swift Testing for new unit tests without rewriting existing XCTest suites.
Go deeper than a summary
Share Your Screen works topics like this through in full: 75 solved Swift problems with tests, 9 real case studies, and 7 annotated mock interviews, so you rehearse the live round instead of just reading about it.
Frequently asked
Should I use Swift Testing or XCTest?
Use Swift Testing for new unit tests; it is the modern default with better diagnostics and parameterization. Keep XCTest for existing suites and UI tests.
Can Swift Testing and XCTest coexist?
Yes. They run in the same test target, so you can add Swift Testing for new tests without migrating your existing XCTest code.