[6.0] Re-apply #1227 Merge tests defined in extensions#1390

ahoppen merged 1 commit intoswiftlang:release/6.0swiftlang/sourcekit-lsp:release/6.0from

ahoppen:6.0/re-apply-1227ahoppen/sourcekit-lsp:6.0/re-apply-1227Copy head branch name to clipboard