Implemented the ArchiveController controller in the library target.

Test/Sources/Helpers/Extensions/Tag+Definitions.swift

@@ -5,6 +5,7 @@ extension Tag {
     // MARK: Constants
     
     @Tag static var builder: Tag
+    @Tag static var controller: Tag
     @Tag static var enumeration: Tag
     @Tag static var middleware: Tag
     @Tag static var provider: Tag

Test/Sources/Helpers/Mocks/FileServiceMock.swift

@@ -0,0 +1,36 @@
+@testable import DoxyLibrary
+
+struct FileServiceMock {
+    
+    // MARK: Properties
+    
+    private let error: FileServiceError?
+    private let items: [String]
+    
+    // MARK: Initialisers
+    
+    init(
+        items: [String] = [],
+        error: FileServiceError? = nil
+    ) {
+        self.error = error
+        self.items = items
+    }
+    
+}
+
+// MARK: - FileServicing
+
+extension FileServiceMock: FileServicing {
+    
+    // MARK: Functions
+    
+    func listItems(in folder: String) async throws(FileServiceError) -> [String] {
+        if let error {
+            throw error
+        }
+        
+        return items
+    }
+    
+}