[Test Improver] Add unit tests for LoggerFactoryProxy

test/UnitTests/Microsoft.Testing.Platform.UnitTests/Logging/LoggerFactoryProxyTests.cs

@@ -0,0 +1,44 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Testing.Platform.Logging;
+
+using Moq;
+
+namespace Microsoft.Testing.Platform.UnitTests;
+
+[TestClass]
+public sealed class LoggerFactoryProxyTests
+{
+    [TestMethod]
+    public void CreateLogger_WhenNotInitialized_ThrowsInvalidOperationException()
+    {
+        LoggerFactoryProxy proxy = new();
+
+        Assert.ThrowsExactly<InvalidOperationException>(() => proxy.CreateLogger("test"));
+    }
+
+    [TestMethod]
+    public void SetLoggerFactory_WithNull_ThrowsArgumentNullException()
+    {
+        LoggerFactoryProxy proxy = new();
+
+        Assert.ThrowsExactly<ArgumentNullException>(() => proxy.SetLoggerFactory(null!));
+    }
+
+    [TestMethod]
+    public void CreateLogger_WhenInitialized_DelegatesToInnerFactory()
+    {
+        Mock<ILogger> mockLogger = new();
+        Mock<ILoggerFactory> mockFactory = new();
+        mockFactory.Setup(f => f.CreateLogger("category")).Returns(mockLogger.Object);
+
+        LoggerFactoryProxy proxy = new();
+        proxy.SetLoggerFactory(mockFactory.Object);
+
+        ILogger result = proxy.CreateLogger("category");
+
+        Assert.AreSame(mockLogger.Object, result);
+        mockFactory.Verify(f => f.CreateLogger("category"), Times.Once);
+    }
+}