Implemented the LogHandlerMock mock type in the tests target.

Tests/DocCMiddleware/Types/Mocks/LogHandlerMock.swift

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+// ===----------------------------------------------------------------------===
+//
+// This source file is part of the Hummingbird DocC Middleware open source project
+//
+// Copyright (c) 2025 Röck+Cöde VoF. and the Hummingbird DocC Middleware project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE for license information
+// See CONTRIBUTORS for the list of Hummingbird DocC Middleware project authors
+//
+// ===----------------------------------------------------------------------===
+
+import Foundation
+
+import protocol Logging.LogHandler
+
+import struct Logging.Logger
+
+/// A mock that conforms to the `LogHandler` protocol.
+struct LogHandlerMock {
+    
+    // MARK: Properties
+
+    /// A representation of the logging level assigned to this mock.
+    private var _logLevel: Logger.Level = .debug
+
+    /// A dictionary that contains all the metadata assigned to this mock.
+    private var _metadata: Logger.Metadata = [:]
+    
+    /// A logging event recorder attached to this mock.
+    private let recorder: LogRecorder = .init()
+
+    // MARK: Computed
+    
+    /// A list of all the logged events that are being persisted in the recorder.
+    var entries: [LogEntry] {
+        get async { await recorder.entries }
+    }
+    
+}
+
+// MARK: - LogEntry
+
+/// A type that contains the information logged in a logging event.
+struct LogEntry: Equatable {
+    
+    // MARK: Properties
+    
+    /// A representation of the level attached to a logged event.
+    let level: Logger.Level
+    
+    /// A metadata dictionary that contains additional information attached to a logged event.
+    let metadata: Logger.Metadata?
+    
+    /// A message attached to a logged event.
+    let message: Logger.Message
+
+    /// A source from where a logged event was triggered.
+    let source: String
+    
+}
+
+// MARK: - LogRecorder
+
+extension LogHandlerMock {
+    /// An actor that persists all the events logged by the ``LogHandlerMock`` mock handler.
+    actor LogRecorder {
+        
+        // MARK: Properties
+        
+        /// A list of all the logged events.
+        private(set) var entries: [LogEntry] = []
+        
+        // MARK: Functions
+        
+        /// Records data related to a logged event.
+        /// - Parameters:
+        ///   - level: A representation of the level attached to a logged event.
+        ///   - metadata: A metadata dictionary that contains additional information attached to a logged event.
+        ///   - message: A message attached to a logged event.
+        ///   - source: A source from where a logged event was triggered.
+        func record(
+            level: Logger.Level,
+            metadata: Logger.Metadata?,
+            message: Logger.Message,
+            source: String
+        ) async {
+            entries += [.init(
+                level: level,
+                metadata: metadata,
+                message: message,
+                source: source
+            )]
+        }
+
+    }
+}
+
+// MARK: - LogHandler
+
+extension LogHandlerMock: LogHandler {
+
+    // MARK: Properties
+    
+    var metadata: Logger.Metadata {
+        get { _metadata }
+        set(newValue) { _metadata = newValue }
+    }
+    
+    var logLevel: Logger.Level {
+        get { _logLevel }
+        set(newValue) { _logLevel = newValue }
+    }
+    
+    // MARK: Subscripts
+    
+    subscript(metadataKey metadataKey: String) -> Logger.Metadata.Value? {
+        get { _metadata[metadataKey] }
+        set(newValue) { _metadata[metadataKey] = newValue }
+    }
+
+    // MARK: Functions
+    
+    func log(
+        level: Logger.Level,
+        message: Logger.Message,
+        metadata: Logger.Metadata?,
+        source: String,
+        file: String,
+        function: String,
+        line: UInt
+    ) {
+        Task { await recorder.record(
+            level: level,
+            metadata: metadata,
+            message: message,
+            source: source
+        )}
+    }
+    
+}