Added the ImageWidth enumeration to the Website library target.

Services/Website/Tests/Library/Cases/Internal/Enumerations/ImageWidthTests.swift

@@ -0,0 +1,24 @@
+import Testing
+
+@testable import WebsiteLibrary
+
+@Suite(
+    "ImageWidth enumeration",
+    .tags(.enumeration)
+)
+struct ImageWidthTests {
+
+    // MARK: Computed tests
+
+    @Test(arguments: zip(
+        ImageWidth.allCases,
+        [480, 800, 1200]
+    ))
+    func `width`(
+        for imageWidth: ImageWidth,
+        expects width: Int
+    ) {
+        #expect(imageWidth.width == width)
+    }
+
+}

Services/Website/Tests/Library/Cases/Internal/Types/StaticFileTests.swift

@@ -33,6 +33,49 @@ struct StaticFileTests {
         #expect(font.urlPath(for: .woff2) == "/font/a-font-400.woff2")
     }
 
+    /// Imagery sits in a folder per page, so a declared folder replaces the extension's own for every extension the file has.
+    @Test
+    func `declared folder paths`() {
+        let portrait = File("portrait", in: "img/about", as: .jpg, .webp)
+
+        #expect(portrait.relativePath(for: .jpg) == "img/about/portrait.jpg")
+        #expect(portrait.relativePath(for: .webp) == "img/about/portrait.webp")
+    }
+
+    // MARK: Methods tests
+
+    @Test(arguments: zip(
+        [AssetExtension.jpg, .webp],
+        ["jpg", "webp"]
+    ))
+    func `srcset offers every rendition narrowest first`(
+        for fileExtension: AssetExtension,
+        expects suffix: String
+    ) {
+        let srcSet = File.srcSet(for: fileExtension) { width in
+            File(
+                width == .large ? "portrait" : "portrait-\(width.width)",
+                in: "img/about",
+                as: .jpg, .webp
+            )
+        }
+
+        #expect(srcSet == [
+            "/img/about/portrait-480.\(suffix) 480w",
+            "/img/about/portrait-800.\(suffix) 800w",
+            "/img/about/portrait.\(suffix) 1200w"
+        ].joined(separator: ", "))
+    }
+
+    @Test
+    func `srcset versions every rendition when given a version`() {
+        let srcSet = File.srcSet(for: .jpg, version: "0123456789abcdef") { _ in
+            File("portrait", in: "img/about", as: .jpg)
+        }
+
+        #expect(srcSet.components(separatedBy: "?v=0123456789abcdef").count - 1 == ImageWidth.allCases.count)
+    }
+
     // MARK: Constants tests
 
     @Test