diff --git a/plist-cil.test/ValuePreprocessorTests.cs b/plist-cil.test/ValuePreprocessorTests.cs
new file mode 100644
index 0000000..af30ce4
--- /dev/null
+++ b/plist-cil.test/ValuePreprocessorTests.cs
@@ -0,0 +1,92 @@
+// plist-cil - An open source library to Parse and generate property lists for .NET
+// Copyright (C) 2015 Natalia Portillo
+//
+// This code is based on:
+// plist - An open source library to Parse and generate property lists
+// Copyright (C) 2014 Daniel Dreibrodt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+using System;
+using System.Linq;
+using Claunia.PropertyList;
+using Xunit;
+
+namespace plistcil.test
+{
+
+    public static class ValuePreprocessorTests
+    {
+        [Fact]
+        public static void TestPassiveDefaultPreprocessorsRegistered()
+        {
+            Assert.Equal(ValuePreprocessor.Preprocess(true, ValuePreprocessor.Types.BOOL), true);
+            Assert.Equal(ValuePreprocessor.Preprocess(false, ValuePreprocessor.Types.BOOL), false);
+            Assert.Equal(ValuePreprocessor.Preprocess("true", ValuePreprocessor.Types.BOOL), "true");
+            Assert.Equal(ValuePreprocessor.Preprocess("42",ValuePreprocessor.Types.INTEGER), "42");
+            Assert.Equal(ValuePreprocessor.Preprocess("3.14159",ValuePreprocessor.Types.FLOATING_POINT), "3.14159");
+            Assert.Equal(ValuePreprocessor.Preprocess("2.71828", ValuePreprocessor.Types.UNDEFINED_NUMBER), "2.71828");
+            Assert.Equal(ValuePreprocessor.Preprocess("TestString",ValuePreprocessor.Types.STRING), "TestString");
+            Assert.Equal(ValuePreprocessor.Preprocess("TestData",ValuePreprocessor.Types.DATA), "TestData");
+            byte[] value = { 0x1, 0x2, 0x4, 0x8 };
+            Assert.Equal(ValuePreprocessor.Preprocess(value,ValuePreprocessor.Types.DATA), value);
+            Assert.Equal(ValuePreprocessor.Preprocess("01.02.1903",ValuePreprocessor.Types.DATE), "01.02.1903");
+            Assert.Equal(ValuePreprocessor.Preprocess(23.0, ValuePreprocessor.Types.DATE), 23.0);
+        }
+
+        [Fact]
+        public static void TestRegisterPreprocessor()
+        {
+            Func<string, string> examplePreprocessor = value => new string(value.Reverse().ToArray());
+            string testString = "TestString";
+            string expected = "gnirtStseT";
+
+            ValuePreprocessor.Register(examplePreprocessor, ValuePreprocessor.Types.STRING);
+            string actual = ValuePreprocessor.Preprocess(testString, ValuePreprocessor.Types.STRING);
+
+            Assert.Equal(actual, expected);
+
+            ValuePreprocessor.Unregister<string>(ValuePreprocessor.Types.STRING);
+        }
+
+        [Fact]
+        public static void TestRegisteredPreprocessorSelection()
+        {
+            Func<string, string> examplePreprocessor = value => new string(value.Reverse().ToArray());
+            string testString = "TestString";
+
+            ValuePreprocessor.Register(examplePreprocessor, ValuePreprocessor.Types.STRING);
+            string actual = ValuePreprocessor.Preprocess(testString, ValuePreprocessor.Types.DATA);
+
+            // assert unchanged, since the selected preprocessor != registered preprocessor
+            Assert.Equal(actual, testString);
+
+            ValuePreprocessor.Unregister<string>(ValuePreprocessor.Types.STRING);
+        }
+
+        [Fact]
+        public static void TestUnregisterdPreprocessorThrows()
+        {
+            byte[] testArray  = { 0x1, 0x2, 0x4, 0x8 };
+
+            // there's no registered preprocessor for byte array arguments for STRING
+            Assert.Throws<ArgumentException>(() => ValuePreprocessor.Preprocess(testArray, ValuePreprocessor.Types.STRING));
+        }
+    }
+}
diff --git a/plist-cil/ValuePreprocessor.cs b/plist-cil/ValuePreprocessor.cs
index 498d48e..f9f9ab6 100644
--- a/plist-cil/ValuePreprocessor.cs
+++ b/plist-cil/ValuePreprocessor.cs
@@ -20,21 +20,24 @@ namespace Claunia.PropertyList
 
         private static readonly Dictionary<TypeIdentifier, Delegate> _preprocessors = new()
         {
-            { new(Types.BOOL, typeof(bool)), NullPreprocessor<bool> },
-            { new(Types.BOOL, typeof(string)), NullPreprocessor<string> },
-            { new(Types.INTEGER, typeof(string)), NullPreprocessor<string> },
-            { new(Types.FLOATING_POINT, typeof(string)), NullPreprocessor<string> },
-            { new(Types.UNDEFINED_NUMBER, typeof(string)), NullPreprocessor<string> },
-            { new(Types.STRING, typeof(string)), NullPreprocessor<string> },
-            { new(Types.DATA, typeof(string)), NullPreprocessor<string> },
-            { new(Types.DATA, typeof(byte[])), NullPreprocessor<byte[]> },
-            { new(Types.DATE, typeof(string)), NullPreprocessor<string> },
-            { new(Types.DATE, typeof(double)), NullPreprocessor<double> },
+            { new TypeIdentifier(Types.BOOL, typeof(bool)), NullPreprocessor<bool> },
+            { new TypeIdentifier(Types.BOOL, typeof(string)), NullPreprocessor<string> },
+            { new TypeIdentifier(Types.INTEGER, typeof(string)), NullPreprocessor<string> },
+            { new TypeIdentifier(Types.FLOATING_POINT, typeof(string)), NullPreprocessor<string> },
+            { new TypeIdentifier(Types.UNDEFINED_NUMBER, typeof(string)), NullPreprocessor<string> },
+            { new TypeIdentifier(Types.STRING, typeof(string)), NullPreprocessor<string> },
+            { new TypeIdentifier(Types.DATA, typeof(string)), NullPreprocessor<string> },
+            { new TypeIdentifier(Types.DATA, typeof(byte[])), NullPreprocessor<byte[]> },
+            { new TypeIdentifier(Types.DATE, typeof(string)), NullPreprocessor<string> },
+            { new TypeIdentifier(Types.DATE, typeof(double)), NullPreprocessor<double> },
         };
 
         public static void Register<T>(Func<T, T> preprocessor, Types type) => 
             _preprocessors[new(type, typeof(T))] = preprocessor;
 
+        public static void Unregister<T>(Types type) =>
+            _preprocessors[new(type, typeof(T))] = NullPreprocessor<T>;
+
         public static T Preprocess<T>(T value, Types type) => 
             TryGetPreprocessor(type, out Func<T, T> preprocess)
                 ? preprocess(value)