diff --git a/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Validation/ModelStateDictionaryTest.cs b/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Validation/ModelStateDictionaryTest.cs
new file mode 100644
index 0000000000..1f94f41290
--- /dev/null
+++ b/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Validation/ModelStateDictionaryTest.cs
@@ -0,0 +1,226 @@
+using System;
+using System.Globalization;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc.ModelBinding
+{
+    public class ModelStateDictionaryTest
+    {
+        [Fact]
+        public void AddModelErrorCreatesModelStateIfNotPresent()
+        {
+            // Arrange
+            var dictionary = new ModelStateDictionary();
+
+            // Act
+            dictionary.AddModelError("some key", "some error");
+
+            // Assert
+            var kvp = Assert.Single(dictionary);
+            Assert.Equal("some key", kvp.Key);
+            var error = Assert.Single(kvp.Value.Errors);
+            Assert.Equal("some error", error.ErrorMessage);
+        }
+
+        [Fact]
+        public void AddModelErrorUsesExistingModelStateIfPresent()
+        {
+            // Arrange
+            var dictionary = new ModelStateDictionary();
+            dictionary.AddModelError("some key", "some error");
+            var ex = new Exception();
+
+            // Act
+            dictionary.AddModelError("some key", ex);
+
+            // Assert
+            var kvp = Assert.Single(dictionary);
+            Assert.Equal("some key", kvp.Key);
+
+            Assert.Equal(2, kvp.Value.Errors.Count);
+            Assert.Equal("some error", kvp.Value.Errors[0].ErrorMessage);
+            Assert.Same(ex, kvp.Value.Errors[1].Exception);
+        }
+
+        [Fact]
+        public void ConstructorWithDictionaryParameter()
+        {
+            // Arrange
+            var oldDictionary = new ModelStateDictionary()
+            {
+                { "foo", new ModelState() { Value = GetValueProviderResult("bar", "bar") } }
+            };
+
+            // Act
+            var newDictionary = new ModelStateDictionary(oldDictionary);
+
+            // Assert
+            Assert.Single(newDictionary);
+            Assert.Equal("bar", newDictionary["foo"].Value.ConvertTo(typeof(string)));
+        }
+
+        [Fact]
+        public void IsValidFieldReturnsFalseIfDictionaryDoesNotContainKey()
+        {
+            // Arrange
+            var msd = new ModelStateDictionary();
+
+            // Act
+            var isValid = msd.IsValidField("foo");
+
+            // Assert
+            Assert.True(isValid);
+        }
+
+        [Fact]
+        public void IsValidFieldReturnsFalseIfKeyChildContainsErrors()
+        {
+            // Arrange
+            var msd = new ModelStateDictionary();
+            msd.AddModelError("foo.bar", "error text");
+
+            // Act
+            var isValid = msd.IsValidField("foo");
+
+            // Assert
+            Assert.False(isValid);
+        }
+
+        [Fact]
+        public void IsValidFieldReturnsFalseIfKeyContainsErrors()
+        {
+            // Arrange
+            var msd = new ModelStateDictionary();
+            msd.AddModelError("foo", "error text");
+
+            // Act
+            var isValid = msd.IsValidField("foo");
+
+            // Assert
+            Assert.False(isValid);
+        }
+
+        [Fact]
+        public void IsValidFieldReturnsTrueIfModelStateDoesNotContainErrors()
+        {
+            // Arrange
+            var msd = new ModelStateDictionary()
+            {
+                { "foo", new ModelState() { Value = new ValueProviderResult(null, null, null) } }
+            };
+
+            // Act
+            var isValid = msd.IsValidField("foo");
+
+            // Assert
+            Assert.True(isValid);
+        }
+
+        [Fact]
+        public void IsValidPropertyReturnsFalseIfErrors()
+        {
+            // Arrange
+            var errorState = new ModelState() { Value = GetValueProviderResult("quux", "quux") };
+            errorState.Errors.Add("some error");
+            var dictionary = new ModelStateDictionary()
+            {
+                { "foo", new ModelState() { Value = GetValueProviderResult("bar", "bar") } },
+                { "baz", errorState }
+            };
+
+            // Act
+            var isValid = dictionary.IsValid;
+
+            // Assert
+            Assert.False(isValid);
+        }
+
+        [Fact]
+        public void IsValidPropertyReturnsTrueIfNoErrors()
+        {
+            // Arrange
+            var dictionary = new ModelStateDictionary()
+            {
+                { "foo", new ModelState() { Value = GetValueProviderResult("bar", "bar") } },
+                { "baz", new ModelState() { Value = GetValueProviderResult("quux", "bar") } }
+            };
+
+            // Act
+            var isValid = dictionary.IsValid;
+
+            // Assert
+            Assert.True(isValid);
+        }
+
+        [Fact]
+        public void MergeCopiesDictionaryEntries()
+        {
+            // Arrange
+            var fooDict = new ModelStateDictionary() { { "foo", new ModelState() } };
+            var barDict = new ModelStateDictionary() { { "bar", new ModelState() } };
+
+            // Act
+            fooDict.Merge(barDict);
+
+            // Assert
+            Assert.Equal(2, fooDict.Count);
+            Assert.Equal(barDict["bar"], fooDict["bar"]);
+        }
+
+        [Fact]
+        public void MergeDoesNothingIfParameterIsNull()
+        {
+            // Arrange
+            var fooDict = new ModelStateDictionary() { { "foo", new ModelState() } };
+
+            // Act
+            fooDict.Merge(null);
+
+            // Assert
+            Assert.Single(fooDict);
+            Assert.True(fooDict.ContainsKey("foo"));
+        }
+
+        [Fact]
+        public void SetAttemptedValueCreatesModelStateIfNotPresent()
+        {
+            // Arrange
+            var dictionary = new ModelStateDictionary();
+
+            // Act
+            dictionary.SetModelValue("some key", GetValueProviderResult("some value", "some value"));
+
+            // Assert
+            Assert.Single(dictionary);
+            var modelState = dictionary["some key"];
+
+            Assert.Empty(modelState.Errors);
+            Assert.Equal("some value", modelState.Value.ConvertTo(typeof(string)));
+        }
+
+        [Fact]
+        public void SetAttemptedValueUsesExistingModelStateIfPresent()
+        {
+            // Arrange
+            var dictionary = new ModelStateDictionary();
+            dictionary.AddModelError("some key", "some error");
+            var ex = new Exception();
+
+            // Act
+            dictionary.SetModelValue("some key", GetValueProviderResult("some value", "some value"));
+
+            // Assert
+            Assert.Single(dictionary);
+            var modelState = dictionary["some key"];
+
+            Assert.Single(modelState.Errors);
+            Assert.Equal("some error", modelState.Errors[0].ErrorMessage);
+            Assert.Equal("some value", modelState.Value.ConvertTo(typeof(string)));
+        }
+
+        private static ValueProviderResult GetValueProviderResult(object rawValue, string attemptedValue)
+        {
+            return new ValueProviderResult(rawValue, attemptedValue, CultureInfo.InvariantCulture);
+        }
+    }
+}