The setting is BUILD_LIBRARY_FOR_DISTRIBUTION. Singular not plural. I was running into this as well and just coded it up.

Clarification: In the actual test I am using XCTAssertNil, the XCTAssertNotNil was added for testing that the test exits on assertion failure. Sorry for the confusion. Either way, validate shouldn't be reached.

This is not an answer but an expanded example: class TestAwaitTests: XCTestCase { struct Thing { let value = true func doSomething() async throws -> Int? { try await Task.sleep(nanoseconds: 5_000_000_000) return 1 } } func validation(thing: Thing, file: StaticString = #file, line: UInt = #line) { XCTAssertFalse(thing.value) XCTAssertTrue(thing.value) // Breakpoint here } func testTest() async throws { continueAfterFailure = false let thing = Thing() let result = try await thing.doSomething() print("print 1") XCTAssertNil(result) print("print 2") XCTAssertNotNil(result) print("print 3") validation(thing: thing) enum Err: Error { case oops } throw Err.oops print("print 4") } } Results in the console output print 1 print 2 print 3 The test fails, as expected. What is unexpected is that the statements print 2 and print 3 are produced. The line marked Breakpoint here should never execute. I can see it hit even in the debugger continueAfterFailure should be stopping the test first assertion.