--- title: Beta Preview: CompilationTesting | daily.dev description: Point-Free released CompilationTesting, a new library for unit testing Swift code that should fail to compile. It runs the Swift compiler on a given snippet... canonical: https://daily.dev/posts/beta-preview-compilationtesting-dlmr3euje twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Beta Preview: CompilationTesting | daily.dev og:description: Point-Free released CompilationTesting, a new library for unit testing Swift code that should fail to compile. It runs the Swift compiler on a given snippet... og:url: https://daily.dev/posts/beta-preview-compilationtesting-dlmr3euje og:image: https://api.daily.dev/og/posts/DlMr3EUJe.png og:image:alt: Beta Preview: CompilationTesting og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Beta Preview: CompilationTesting **[Point-Free Pointers](https://daily.dev/sources/pointfree)** · 5 min read · 0 upvotes · 0 comments ## Summary Point-Free released CompilationTesting, a new library for unit testing Swift code that should fail to compile. It runs the Swift compiler on a given snippet and records its errors, warnings, fix-its, and notes as an inline snapshot inside the test file. It builds on the InlineSnapshotTesting library, the same engine behind MacroTesting. It can import your own package's modules and macro plugins, letting you test deprecation warnings, macro-generated type errors, and behavior across Swift language modes like 5, 6, and 4 using flags such as `.languageMode(.v6)`. It's available now as a beta preview exclusively for Point-Free Max members. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How can I write a unit test that verifies a Swift snippet fails to compile with a specific error? Use the CompilationTesting library's `assertCompilation` function, passing the Swift source as a string and a trailing `diagnostics` closure. On first run it inserts the diagnostics closure automatically, snapshotting the compiler's error, warning, or fix-it text; rerunning verifies it, and any future change to the diagnostics fails the test with a diff. _daily.dev surfaces library updates like this for Swift developers hardening their compile-time guarantees._ ### How do I test that my Swift macro produces the correct compiler error when used incorrectly? CompilationTesting automatically loads macro plugins built by your package, so you can write a snippet importing the macro and applying it to invalid code, then snapshot the resulting diagnostic. For example, applying a `@DeriveEquatable` macro to a struct with a non-Equatable field produces an error like "'Avatar' does not conform to 'Equatable'", which gets recorded inline. _Developers testing macro correctness can track tools like this via daily.dev before adopting them._ ### How can I test Swift code behavior differently across Swift 5 and Swift 6 language modes? Pass a `flags` parameter to `assertCompilation` with `.languageMode(.v5)` or `.languageMode(.v6)`, or apply a `.compilation(flags:)` trait to an entire test suite. For instance, a class with a non-Sendable static `shared` property compiles cleanly under Swift 5 mode but would fail under Swift 6 mode, which requires globals to be Sendable. _daily.dev helps developers navigating Swift language mode migrations stay on top of tooling changes._ ## Similar posts on daily.dev - [Introducing: Point-Free Beta Previews](https://daily.dev/posts/introducing-point-free-beta-previews-caohf7a5h) · Point-Free Pointers · 0 upvotes · 0 comments - [Introducing: The Point-Free Way](https://daily.dev/posts/introducing-the-point-free-way-hdjokij8f) · Point-Free Pointers · 0 upvotes · 0 comments - [Swift Testing explained with code examples](https://daily.dev/posts/swift-testing-explained-with-code-examples-pgxkvbvk5) · SwiftLee · 1 upvotes · 0 comments - [Just Testing: Applicative Code \(@code.applicative.co\)](https://daily.dev/posts/just-testing-applicative-code-code-applicative-co--fjdvt5gtr) · Planet Haskell · 0 upvotes · 0 comments - [Last Month in Point-Free: August](https://daily.dev/posts/last-month-in-point-free-august-pqnhdhglw) · Point-Free Pointers · 0 upvotes · 0 comments --- Tags: [#testing](https://daily.dev/tags/testing), [#swift](https://daily.dev/tags/swift) [View this post on daily.dev](https://daily.dev/posts/beta-preview-compilationtesting-dlmr3euje) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Beta Preview: CompilationTesting","url":"https://daily.dev/posts/beta-preview-compilationtesting-dlmr3euje","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/beta-preview-compilationtesting-dlmr3euje"},"datePublished":"2026-10-26T00:02:37.269Z","dateModified":"2026-10-26T00:03:17.808Z","description":"Point-Free released CompilationTesting, a new library for unit testing Swift code that should fail to compile. 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On first run it inserts the diagnostics closure automatically, snapshotting the compiler's error, warning, or fix-it text; rerunning verifies it, and any future change to the diagnostics fails the test with a diff. daily.dev surfaces library updates like this for Swift developers hardening their compile-time guarantees."}},{"@type":"Question","name":"How do I test that my Swift macro produces the correct compiler error when used incorrectly?","acceptedAnswer":{"@type":"Answer","text":"CompilationTesting automatically loads macro plugins built by your package, so you can write a snippet importing the macro and applying it to invalid code, then snapshot the resulting diagnostic. For example, applying a `@DeriveEquatable` macro to a struct with a non-Equatable field produces an error like \"'Avatar' does not conform to 'Equatable'\", which gets recorded inline. 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