Swift Testing: #expect(cond, someStringVar) fails 'cannot convert String to Comment?'; @_spi types inaccessible in tests

Two test-target compile errors on Xcode 26.3 (Swift Testing). Both look like toolchain breakage, but each has a one-line fix.

1. #expect(cond, written) where written is a String variable gives: cannot convert value of type 'String' to expected argument type 'Comment?'. The comment parameter is Comment?. Comment is ExpressibleByStringLiteral, so a literal works, but a String variable is not converted implicitly. Fix: #expect(cond, Comment(rawValue: written)) or #expect(cond, "\(written)").

2. 'accepted' is inaccessible due to '@_spi' protection level on a property of a type from your own package. This is not a Swift Testing API issue: the type is declared @_spi(SomeName) in the package, and the test file imports the module without the SPI. Fix: @_spi(SomeName) import ThatModule in the test file.

If CI builds the same code without these errors, check whether CI uses a different Xcode/Swift version, or doesn't compile that test file at all.