diff --git a/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemTests.cs b/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemTests.cs
index 34fc81400..513460d3b 100644
--- a/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemTests.cs
+++ b/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemTests.cs
@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Linq;
 using System.Reflection;
 using System.Text;
@@ -304,5 +305,39 @@ public void MockFileSystem_DefaultState_CurrentDirectoryExists(string currentDir
 
             Assert.IsTrue(actualCurrentDirectory.Exists);
         }
+
+        [Test]
+        public void MockFileSystem_FileSystemWatcher_ShouldBeAssignable()
+        {
+            var path = XFS.Path(@"C:\root");
+            var fileSystem = new MockFileSystem {FileSystemWatcher = new TestFileSystemWatcherFactory()};
+            var watcher = fileSystem.FileSystemWatcher.FromPath(path);
+            Assert.AreEqual(path, watcher.Path);
+        }
+
+        private class TestFileSystemWatcherFactory : IFileSystemWatcherFactory
+        {
+            public FileSystemWatcherBase CreateNew() => new TestFileSystemWatcher(null);
+            public FileSystemWatcherBase FromPath(string path) => new TestFileSystemWatcher(path);
+        }
+
+        private class TestFileSystemWatcher : FileSystemWatcherBase
+        {
+            public TestFileSystemWatcher(string path) => Path = path;
+            public override string Path { get; set; }
+            public override bool IncludeSubdirectories { get; set; }
+            public override bool EnableRaisingEvents { get; set; }
+            public override string Filter { get; set; }
+            public override int InternalBufferSize { get; set; }
+            public override NotifyFilters NotifyFilter { get; set; }
+#if NET40
+            public override ISite Site { get; set; }
+            public override ISynchronizeInvoke SynchronizingObject { get; set; }
+            public override void BeginInit() {}
+            public override void EndInit() {}
+#endif
+            public override WaitForChangedResult WaitForChanged(WatcherChangeTypes changeType) => default(WaitForChangedResult);
+            public override WaitForChangedResult WaitForChanged(WatcherChangeTypes changeType, int timeout) => default(WaitForChangedResult);
+        }
     }
 }
diff --git a/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemWatcherFactoryTests.cs b/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemWatcherFactoryTests.cs
index 53cc83ec5..49696508a 100644
--- a/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemWatcherFactoryTests.cs
+++ b/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemWatcherFactoryTests.cs
@@ -1,8 +1,5 @@
 using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
+using XFS = System.IO.Abstractions.TestingHelpers.MockUnixSupport;
 
 namespace System.IO.Abstractions.TestingHelpers.Tests
 {
@@ -10,43 +7,18 @@ namespace System.IO.Abstractions.TestingHelpers.Tests
     public class MockFileSystemWatcherFactoryTests
     {
         [Test]
-        public void MockFileSystemWatcherFactory_CreateNew_ShouldReturnNonNullMockWatcher()
+        public void MockFileSystemWatcherFactory_CreateNew_ShouldThrowNotImplementedException()
         {
-            // Arrange
             var factory = new MockFileSystemWatcherFactory();
-
-            // Act
-            var result = factory.CreateNew();
-
-            // Assert
-            Assert.IsNotNull(result);
+            Assert.Throws<NotImplementedException>(() => factory.CreateNew());
         }
 
         [Test]
-        public void MockFileSystemWatcherFactory_FromPath_ShouldReturnNonNullMockWatcher()
+        public void MockFileSystemWatcherFactory_FromPath_ShouldThrowNotImplementedException()
         {
-            // Arrange
+            var path = XFS.Path(@"y:\test");
             var factory = new MockFileSystemWatcherFactory();
-
-            // Act
-            var result = factory.FromPath(@"y:\test");
-
-            // Assert
-            Assert.IsNotNull(result);
-        }
-
-        [Test]
-        public void MockFileSystemWatcherFactory_FromPath_ShouldReturnWatcherForSpecifiedPath()
-        {
-            // Arrange
-            const string path = @"z:\test";
-            var factory = new MockFileSystemWatcherFactory();
-
-            // Act
-            var result = factory.FromPath(path);
-
-            // Assert
-            Assert.AreEqual(path, result.Path);
+            Assert.Throws<NotImplementedException>(() => factory.FromPath(path));
         }
     }
 }
diff --git a/System.IO.Abstractions.TestingHelpers/MockFileSystem.cs b/System.IO.Abstractions.TestingHelpers/MockFileSystem.cs
index ca540cd51..f66d2f7f8 100644
--- a/System.IO.Abstractions.TestingHelpers/MockFileSystem.cs
+++ b/System.IO.Abstractions.TestingHelpers/MockFileSystem.cs
@@ -65,7 +65,7 @@ public MockFileSystem(IDictionary<string, MockFileData> files, string currentDir
 
         public IDriveInfoFactory DriveInfo { get; }
 
-        public IFileSystemWatcherFactory FileSystemWatcher { get; }
+        public IFileSystemWatcherFactory FileSystemWatcher { get; set; }
 
         public IFileSystem FileSystem => this;
 
diff --git a/System.IO.Abstractions.TestingHelpers/MockFileSystemWatcher.cs b/System.IO.Abstractions.TestingHelpers/MockFileSystemWatcher.cs
deleted file mode 100644
index a1204412d..000000000
--- a/System.IO.Abstractions.TestingHelpers/MockFileSystemWatcher.cs
+++ /dev/null
@@ -1,38 +0,0 @@
-using System.ComponentModel;
-
-namespace System.IO.Abstractions.TestingHelpers
-{
-    public class MockFileSystemWatcher : FileSystemWatcherBase
-    {
-        public override bool IncludeSubdirectories { get; set; }
-        public override bool EnableRaisingEvents { get; set; }
-        public override string Filter { get; set; }
-        public override int InternalBufferSize { get; set; }
-        public override NotifyFilters NotifyFilter { get; set; }
-        public override string Path { get; set; }
-#if NET40
-        public override ISite Site { get; set; }
-        public override ISynchronizeInvoke SynchronizingObject { get; set; }
-#endif
-
-#if NET40
-        public override void BeginInit()
-        {
-        }
-
-        public override void EndInit()
-        {
-        }
-#endif
-
-        public override WaitForChangedResult WaitForChanged(WatcherChangeTypes changeType)
-        {
-            throw new NotImplementedException();
-        }
-
-        public override WaitForChangedResult WaitForChanged(WatcherChangeTypes changeType, int timeout)
-        {
-            throw new NotImplementedException();
-        }
-    }
-}
diff --git a/System.IO.Abstractions.TestingHelpers/MockFileSystemWatcherFactory.cs b/System.IO.Abstractions.TestingHelpers/MockFileSystemWatcherFactory.cs
index 14a494074..fa832ba13 100644
--- a/System.IO.Abstractions.TestingHelpers/MockFileSystemWatcherFactory.cs
+++ b/System.IO.Abstractions.TestingHelpers/MockFileSystemWatcherFactory.cs
@@ -1,21 +1,12 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-
-namespace System.IO.Abstractions.TestingHelpers
+namespace System.IO.Abstractions.TestingHelpers
 {
     [Serializable]
     public class MockFileSystemWatcherFactory : IFileSystemWatcherFactory
     {
-        public FileSystemWatcherBase CreateNew()
-        {
-            return new MockFileSystemWatcher();
-        }
+        public FileSystemWatcherBase CreateNew() =>
+            throw new NotImplementedException(StringResources.Manager.GetString("FILE_SYSTEM_WATCHER_NOT_IMPLEMENTED_EXCEPTION"));
 
-        public FileSystemWatcherBase FromPath(string path)
-        {
-            return new MockFileSystemWatcher {Path = path};
-        }
+        public FileSystemWatcherBase FromPath(string path) =>
+            throw new NotImplementedException(StringResources.Manager.GetString("FILE_SYSTEM_WATCHER_NOT_IMPLEMENTED_EXCEPTION"));
     }
 }
diff --git a/System.IO.Abstractions.TestingHelpers/Properties/Resources.resx b/System.IO.Abstractions.TestingHelpers/Properties/Resources.resx
index 5e8750581..13097ff13 100644
--- a/System.IO.Abstractions.TestingHelpers/Properties/Resources.resx
+++ b/System.IO.Abstractions.TestingHelpers/Properties/Resources.resx
@@ -144,4 +144,7 @@
   <data name="COULD_NOT_FIND_FILE_EXCEPTION" xml:space="preserve">
     <value>Could not find file '{0}'.</value>
   </data>
-</root>
\ No newline at end of file
+  <data name="FILE_SYSTEM_WATCHER_NOT_IMPLEMENTED_EXCEPTION" xml:space="preserve">
+    <value>MockFileSystem does not have a built-in FileSystemWatcher implementation. You must provide your own mock or implementation of IFileSystemWatcherFactory and assign it to MockFileSystem.FileSystemWatcher.</value>
+  </data>
+</root>