Initial commit.

Packages/Localization/Tests/Cases/Public/Methods/LocalizeTests.swift

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+import Foundation
+import Testing
+
+@testable import Localization
+
+@Suite(
+    "Localize method",
+    .tags(.method)
+)
+struct LocalizeTests {
+    
+    // MARK: Constants
+    
+    private let localize = Localize(bundle: .module)
+
+    // MARK: Functional tests
+
+    @Test
+    func `resolves a key in the default locale`() {
+        let text = localize(
+            "test.greeting",
+            locale: Locale(identifier: "en")
+        )
+
+        #expect(text == "Hello")
+    }
+
+    @Test
+    func `resolves a key in another locale`() {
+        let text = localize(
+            "test.greeting",
+            locale: Locale(identifier: "de"),
+        )
+
+        #expect(text == "Hallo")
+    }
+
+    @Test
+    func `resolves a key in a regional locale`() {
+        let text = localize(
+            "test.greeting",
+            locale: Locale(identifier: "pt-BR"),
+        )
+
+        #expect(text == "Olá")
+    }
+
+    @Test
+    func `falls back to the primary language for an unmatched regional locale`() {
+        let text = localize(
+            "test.greeting",
+            locale: Locale(identifier: "de-AT"),
+        )
+
+        #expect(text == "Hallo")
+    }
+
+    @Test
+    func `falls back to the source language for an unsupported locale`() {
+        let text = localize(
+            "test.greeting",
+            locale: Locale(identifier: "fr"),
+        )
+
+        #expect(text == "Hello")
+    }
+
+    @Test
+    func `falls back to the key for an unknown entry`() {
+        let text = localize(
+            "unknown.key",
+            locale: Locale(identifier: "en"),
+        )
+
+        #expect(text == "unknown.key")
+    }
+
+    @Test
+    func `falls back to the key for a missing catalog`() {
+        let localize = Localize(bundle: .main)
+
+        let text = localize(
+            "test.greeting",
+            locale: Locale(identifier: "en")
+        )
+
+        #expect(text == "test.greeting")
+    }
+
+    // MARK: Properties tests
+
+    @Test
+    func `reports a loaded catalog`() {
+        #expect(localize.catalogState == .loaded)
+    }
+
+    @Test
+    func `reports a missing catalog`() {
+        let localize = Localize(bundle: .main)
+
+        #expect(localize.catalogState == .missing)
+    }
+
+    // A malformed catalog cannot ship as a test resource — Xcode generates string symbols for every
+    // bundled `.xcstrings` and fails the build on invalid JSON — so one is staged in a temporary
+    // directory bundle instead.
+    @Test
+    func `reports an undecodable catalog`() throws {
+        let directory = URL(fileURLWithPath: NSTemporaryDirectory())
+            .appendingPathComponent(
+                "UndecodableCatalog-\(UUID().uuidString)",
+                isDirectory: true
+            )
+
+        try FileManager.default.createDirectory(
+            at: directory,
+            withIntermediateDirectories: true
+        )
+
+        defer {
+            try? FileManager.default.removeItem(at: directory)
+        }
+
+        try Data("not a catalog".utf8).write(
+            to: directory.appendingPathComponent("Localizable.xcstrings")
+        )
+
+        let bundle = try #require(Bundle(url: directory))
+        let localize = Localize(bundle: bundle)
+
+        #expect(localize.catalogState == .undecodable)
+    }
+
+}

Packages/Localization/Tests/Cases/Public/Methods/NegotiateTests.swift

@@ -0,0 +1,130 @@
+import Foundation
+import Testing
+
+@testable import Localization
+
+@Suite(
+    "Negotiate method",
+    .tags(.method)
+)
+struct NegotiateTests {
+
+    // MARK: Constants
+
+    private let negotiate = Negotiate(bundle: .module)
+
+    // MARK: Functional tests
+
+    @Test
+    func `matches an exact language tag`() {
+        let language = negotiate(acceptLanguage: "de")
+
+        #expect(language == "de")
+    }
+
+    @Test
+    func `matches a regional language tag`() {
+        let language = negotiate(acceptLanguage: "de-AT")
+
+        #expect(language == "de")
+    }
+
+    @Test
+    func `matches a regional catalog language exactly`() {
+        let language = negotiate(acceptLanguage: "pt-BR")
+
+        #expect(language == "pt-BR")
+    }
+
+    @Test
+    func `matches a regional catalog language by its primary subtag`() {
+        let language = negotiate(acceptLanguage: "pt")
+
+        #expect(language == "pt-BR")
+    }
+
+    @Test
+    func `respects the header order of preference`() {
+        let language = negotiate(acceptLanguage: "de, en")
+
+        #expect(language == "de")
+    }
+
+    @Test
+    func `orders the language tags by descending quality weight`() {
+        let language = negotiate(acceptLanguage: "en;q=0.5, de;q=0.9")
+
+        #expect(language == "de")
+    }
+
+    @Test
+    func `treats a tag without a weight as the highest preference`() {
+        let language = negotiate(acceptLanguage: "en;q=0.9, de")
+
+        #expect(language == "de")
+    }
+
+    @Test
+    func `treats a tag with a malformed weight as the highest preference`() {
+        let language = negotiate(acceptLanguage: "en;q=0.9, de;q=broken")
+
+        #expect(language == "de")
+    }
+
+    @Test
+    func `drops language tags weighted as not acceptable`() {
+        let language = negotiate(acceptLanguage: "de;q=0, en;q=0.8")
+
+        #expect(language == "en")
+    }
+
+    @Test
+    func `falls back to the default when every tag is weighted as not acceptable`() {
+        let language = negotiate(acceptLanguage: "de;q=0, fr;q=0")
+
+        #expect(language == "en")
+    }
+
+    @Test
+    func `serves the default language for a wildcard`() {
+        let language = negotiate(acceptLanguage: "fr;q=0.9, *;q=0.5")
+
+        #expect(language == "en")
+    }
+
+    @Test
+    func `trims whitespace around the language tags`() {
+        let language = negotiate(acceptLanguage: " de , en ")
+
+        #expect(language == "de")
+    }
+
+    @Test
+    func `falls back to the default for an unsupported language`() {
+        let language = negotiate(acceptLanguage: "fr")
+
+        #expect(language == "en")
+    }
+
+    @Test
+    func `falls back to the default for a missing header`() {
+        let language = negotiate(acceptLanguage: nil)
+
+        #expect(language == "en")
+    }
+
+    @Test
+    func `falls back to the default for an empty header`() {
+        let language = negotiate(acceptLanguage: "")
+
+        #expect(language == "en")
+    }
+
+    @Test
+    func `falls back to the default for a header without language tags`() {
+        let language = negotiate(acceptLanguage: " , ;q=0.5,")
+
+        #expect(language == "en")
+    }
+
+}

Packages/Localization/Tests/Cases/Public/Types/LanguageListTests.swift

@@ -0,0 +1,105 @@
+import Foundation
+import Testing
+
+@testable import Localization
+
+@Suite(
+    "LanguageList type",
+    .tags(.type)
+)
+struct LanguageListTests {
+
+    // MARK: Properties tests
+
+    @Suite("default")
+    struct Default {
+        @Test
+        func `defaults to english`() {
+            let list = LanguageList(
+                bundle: .module
+            )
+
+            #expect(list.default == "en")
+        }
+
+        @Test
+        func `follows the catalog's source language`() {
+            let list = LanguageList(
+                resolver: StubCatalog(
+                    sourceLanguage: "de",
+                    languages: ["de", "en"]
+                )
+            )
+
+            #expect(list.default == "de")
+        }
+    }
+
+    @Suite("catalogState")
+    struct CatalogState {
+        @Test
+        func `reports a loaded catalog`() {
+            let list = LanguageList(
+                bundle: .module
+            )
+
+            #expect(list.catalogState == .loaded)
+        }
+
+        @Test
+        func `reports a missing catalog`() {
+            let list = LanguageList(
+                bundle: .main
+            )
+
+            #expect(list.catalogState == .missing)
+        }
+    }
+
+    @Suite("all")
+    struct All {
+        @Test
+        func `lists the catalog languages`() {
+            let list = LanguageList(
+                bundle: .module
+            )
+
+            #expect(list.all.contains("en"))
+            #expect(list.all.contains("de"))
+        }
+
+        @Test
+        func `excludes the base localization`() {
+            let list = LanguageList(
+                resolver: StubCatalog(
+                    sourceLanguage: "en",
+                    languages: ["Base", "de", "en"]
+                )
+            )
+
+            #expect(list.all == ["de", "en"])
+        }
+
+        @Test
+        func `sorts the languages`() {
+            let list = LanguageList(
+                resolver: StubCatalog(
+                    sourceLanguage: "en",
+                    languages: ["fr", "en", "de"]
+                )
+            )
+
+            #expect(list.all == ["de", "en", "fr"])
+        }
+
+        @Test
+        func `degrades to the default language for a missing catalog`() {
+            let list = LanguageList(
+                bundle: .main
+            )
+
+            #expect(list.all == ["en"])
+        }
+    }
+
+}

Packages/Localization/Tests/Catalogs/Localizable.xcstrings

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+{
+  "sourceLanguage" : "en",
+  "strings" : {
+    "test.greeting" : {
+      "comment" : "Fixture string used by the Localization test suite.",
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Hallo"
+          }
+        },
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Hello"
+          }
+        },
+        "pt-BR" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Olá"
+          }
+        }
+      }
+    }
+  },
+  "version" : "1.0"
+}

Packages/Localization/Tests/Utils/Extensions/Tag+Constants.swift

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+import Testing
+
+extension Tag {
+    /// Tests exercising a method of the Localization package.
+    @Tag static var method: Tag
+    /// Tests exercising a type of the Localization package.
+    @Tag static var type: Tag
+}

Packages/Localization/Tests/Utils/Resolvers/StubCatalog.swift

@@ -0,0 +1,23 @@
+import Foundation
+
+@testable import Localization
+
+/// A ``CatalogResolving`` backend with fixed languages, for exercising types apart from a bundled catalog.
+struct StubCatalog: CatalogResolving {
+
+    // MARK: Properties
+
+    let sourceLanguage: String
+    let languages: Set<String>
+    var state: CatalogState = .loaded
+
+    // MARK: Methods
+
+    func string(
+        for key: String,
+        in locale: Locale
+    ) -> String {
+        key
+    }
+
+}