diff --git a/src/NUnitEngine/nunit.engine.core.tests/Internal/AddinsFileTests.cs b/src/NUnitEngine/nunit.engine.core.tests/Internal/AddinsFileTests.cs
new file mode 100644
index 000000000..25d4363b1
--- /dev/null
+++ b/src/NUnitEngine/nunit.engine.core.tests/Internal/AddinsFileTests.cs
@@ -0,0 +1,93 @@
+// Copyright (c) Charlie Poole, Rob Prouse and Contributors. MIT License - see LICENSE.txt
+
+using NUnit.Engine.Internal.FileSystemAccess;
+using NUnit.Framework;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+
+namespace NUnit.Engine.Internal.Tests
+{
+    /// <summary>
+    /// Tests the implementation of <see cref="AddinsFile"/>.
+    /// </summary>
+    [TestFixture]
+    public class AddinsFileTests
+    {
+        [Test]
+        public void Read_IFile_Null()
+        {
+            Assert.That(() => AddinsFile.Read((IFile)null), Throws.ArgumentNullException);
+        }
+
+        [Test]
+        public void Read_Stream()
+        {
+            var content = new[]
+            {
+                "# This line is a comment and is ignored. The next (blank) line is ignored as well.",
+                "",
+                "*.dll                   # include all dlls in the same directory",
+                "addins/*.dll            # include all dlls in the addins directory too",
+                "special/myassembly.dll  # include a specific dll in a special directory",
+                "some/other/directory/  # process another directory, which may contain its own addins file",
+                "# note that an absolute path is allowed, but is probably not a good idea in most cases",
+                "/unix/absolute/directory"
+            };
+
+            using (var stream = new MemoryStream(Encoding.UTF8.GetBytes(string.Join(Environment.NewLine, content))))
+            {
+                var result = AddinsFile.Read(stream);
+
+                Assert.That(result, Has.Count.EqualTo(8));
+                for (int i = 0; i < 8; i++)
+                    Assert.That(result[i], Is.EqualTo(
+                        new AddinsFileEntry(i + 1, content[i])));
+            }
+        }
+
+        [Test]
+        public void Read_InvalidEntry()
+        {
+            var content = "// This is not valid";
+            using (var stream = new MemoryStream(Encoding.UTF8.GetBytes(content)))
+            {
+                Assert.That(() => AddinsFile.Read(stream), Throws.Exception);
+            }
+        }
+
+        [Test]
+        [Platform("win")]
+        public void Read_Stream_TransformBackslash_Windows()
+        {
+            var content = "c:\\windows\\absolute\\directory";
+
+            using (var stream = new MemoryStream(Encoding.UTF8.GetBytes(content)))
+            {
+                var result = AddinsFile.Read(stream);
+
+                Assert.That(result, Has.Count.EqualTo(1));
+                Assert.That(result[0], Is.EqualTo(new AddinsFileEntry(1, content)));
+                Assert.That(result[0].Text, Is.EqualTo("c:/windows/absolute/directory"));
+            }
+        }
+
+        [Test]
+        [Platform("linux,macosx,unix")]
+        public void Read_Stream_TransformBackslash_NonWindows()
+        {
+            var content = "this/is/a\\ path\\ with\\ spaces/";
+
+            using (var stream = new MemoryStream(Encoding.UTF8.GetBytes(content)))
+            {
+                var result = AddinsFile.Read(stream);
+
+                Assert.That(result, Has.Count.EqualTo(1));
+                Assert.That(result[0], Is.EqualTo(new AddinsFileEntry(1, content)));
+                Assert.That(result[0].Text, Is.EqualTo(content));
+            }
+        }
+    }
+}