diff --git a/source/TestFramework/CallerArgumentExpressionAttribute.cs b/source/TestFramework/CallerArgumentExpressionAttribute.cs
deleted file mode 100644
index ec3fb98..0000000
--- a/source/TestFramework/CallerArgumentExpressionAttribute.cs
+++ /dev/null
@@ -1,27 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-
-// ReSharper disable once CheckNamespace
-namespace System.Runtime.CompilerServices
-{
-    /// <summary>
-    /// Indicates that a parameter captures the expression passed for another parameter as a string.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
-    internal sealed class CallerArgumentExpressionAttribute : Attribute
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="CallerArgumentExpressionAttribute"/> class.
-        /// </summary>
-        /// <param name="parameterName">The name of the parameter whose expression should be captured as a string.</param>
-        public CallerArgumentExpressionAttribute(string parameterName)
-        {
-            ParameterName = parameterName;
-        }
-
-        /// <summary>
-        /// Gets the name of the parameter whose expression should be captured as a string.
-        /// </summary>
-        public string ParameterName { get; }
-    }
-}
\ No newline at end of file
diff --git a/source/TestFramework/NullableAttributes.cs b/source/TestFramework/NullableAttributes.cs
deleted file mode 100644
index e36c7e6..0000000
--- a/source/TestFramework/NullableAttributes.cs
+++ /dev/null
@@ -1,181 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-
-// ReSharper disable once CheckNamespace
-namespace System.Diagnostics.CodeAnalysis
-{
-    /// <summary>
-    /// Specifies that <see langword="null"/> is allowed as an input even if the corresponding type disallows it.
-    /// </summary>
-    /// <remarks>
-    /// To override a method that has a parameter annotated with this attribute, use the ? operator. For more information, see Nullable static analysis in the C# guide.
-    /// </remarks>
-    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
-    internal sealed class AllowNullAttribute : Attribute
-    { }
-
-    /// <summary>
-    /// Specifies that null is disallowed as an input even if the corresponding type allows it.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
-    internal sealed class DisallowNullAttribute : Attribute
-    { }
-
-    /// <summary>
-    /// Specifies that an output may be null even if the corresponding type disallows it.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
-    internal sealed class MaybeNullAttribute : Attribute
-    { }
-
-    /// <summary>
-    /// Specifies that an output will not be null even if the corresponding type allows it. Specifies that an input argument was not null when the call returns.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
-    internal sealed class NotNullAttribute : Attribute
-    { }
-
-    /// <summary>
-    /// Specifies that when a method returns <see cref="ReturnValue"/>, the parameter may be null even if the corresponding type disallows it.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
-    internal sealed class MaybeNullWhenAttribute : Attribute
-    {
-        /// <summary>
-        /// Initializes the attribute with the specified return value condition.
-        /// </summary>
-        /// <param name="returnValue">
-        /// The return value condition. If the method returns this value, the associated parameter may be null.
-        /// </param>
-        internal MaybeNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;
-
-        /// <summary>
-        /// Gets the return value condition.
-        /// </summary>
-        internal bool ReturnValue { get; }
-    }
-
-    /// <summary>
-    /// Specifies that when a method returns <see cref="ReturnValue"/>, the parameter will not be null even if the corresponding type allows it.
-    /// </summary>
-    internal sealed class NotNullWhenAttribute : Attribute
-    {
-        /// <summary>Initializes the attribute with the specified return value condition.</summary>
-        /// <param name="returnValue">
-        /// The return value condition. If the method returns this value, the associated parameter will not be null.
-        /// </param>
-        internal NotNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;
-
-        /// <summary>Gets the return value condition.</summary>
-        internal bool ReturnValue { get; }
-    }
-
-    /// <summary>
-    /// Specifies that the output will be non-null if the named parameter is non-null.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, AllowMultiple = true, Inherited = false)]
-    internal sealed class NotNullIfNotNullAttribute : Attribute
-    {
-        /// <summary>Initializes the attribute with the associated parameter name.</summary>
-        /// <param name="parameterName">
-        /// The associated parameter name.  The output will be non-null if the argument to the parameter specified is non-null.
-        /// </param>
-        internal NotNullIfNotNullAttribute(string parameterName) => ParameterName = parameterName;
-
-        /// <summary>Gets the associated parameter name.</summary>
-        internal string ParameterName { get; }
-    }
-
-    /// <summary>
-    /// Applied to a method that will never return under any circumstance.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
-    internal sealed class DoesNotReturnAttribute : Attribute
-    { }
-
-    /// <summary>
-    /// Specifies that the method will not return if the associated Boolean parameter is passed the specified value.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
-    internal sealed class DoesNotReturnIfAttribute : Attribute
-    {
-        /// <summary>Initializes the attribute with the specified parameter value.</summary>
-        /// <param name="parameterValue">
-        /// The condition parameter value. Code after the method will be considered unreachable by diagnostics if the argument to
-        /// the associated parameter matches this value.
-        /// </param>
-        internal DoesNotReturnIfAttribute(bool parameterValue) => ParameterValue = parameterValue;
-
-        /// <summary>
-        /// Gets the condition parameter value.
-        /// </summary>
-        internal bool ParameterValue { get; }
-    }
-
-    /// <summary>
-    /// Specifies that the method or property will ensure that the listed field and property members have not-null values.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
-    internal sealed class MemberNotNullAttribute : Attribute
-    {
-        /// <summary>Initializes the attribute with a field or property member.</summary>
-        /// <param name="member">
-        /// The field or property member that is promised to be not-null.
-        /// </param>
-        internal MemberNotNullAttribute(string member) => Members = new[] { member };
-
-        /// <summary>Initializes the attribute with the list of field and property members.</summary>
-        /// <param name="members">
-        /// The list of field and property members that are promised to be not-null.
-        /// </param>
-        internal MemberNotNullAttribute(params string[] members) => Members = members;
-
-        /// <summary>
-        /// Gets field or property member names.
-        /// </summary>
-        internal string[] Members { get; }
-    }
-
-    /// <summary>
-    /// Specifies that the method or property will ensure that the listed field and property members have not-null values when returning with the specified return value condition.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
-    internal sealed class MemberNotNullWhenAttribute : Attribute
-    {
-        /// <summary>Initializes the attribute with the specified return value condition and a field or property member.</summary>
-        /// <param name="returnValue">
-        /// The return value condition. If the method returns this value, the associated parameter will not be null.
-        /// </param>
-        /// <param name="member">
-        /// The field or property member that is promised to be not-null.
-        /// </param>
-        internal MemberNotNullWhenAttribute(bool returnValue, string member)
-        {
-            ReturnValue = returnValue;
-            Members = new[] { member };
-        }
-
-        /// <summary>Initializes the attribute with the specified return value condition and list of field and property members.</summary>
-        /// <param name="returnValue">
-        /// The return value condition. If the method returns this value, the associated parameter will not be null.
-        /// </param>
-        /// <param name="members">
-        /// The list of field and property members that are promised to be not-null.
-        /// </param>
-        internal MemberNotNullWhenAttribute(bool returnValue, params string[] members)
-        {
-            ReturnValue = returnValue;
-            Members = members;
-        }
-
-        /// <summary>
-        /// Gets the return value condition.
-        /// </summary>
-        internal bool ReturnValue { get; }
-
-        /// <summary>
-        /// Gets field or property member names.
-        /// </summary>
-        internal string[] Members { get; }
-    }
-}
diff --git a/source/TestFramework/nanoFramework.TestFramework.nfproj b/source/TestFramework/nanoFramework.TestFramework.nfproj
index e6c6b6d..aef9a17 100644
--- a/source/TestFramework/nanoFramework.TestFramework.nfproj
+++ b/source/TestFramework/nanoFramework.TestFramework.nfproj
@@ -42,9 +42,7 @@
     <Compile Include="Assert.Obsolete.cs">
       <DependentUpon>Assert.cs</DependentUpon>
     </Compile>
-    <Compile Include="CallerArgumentExpressionAttribute.cs" />
     <Compile Include="CollectionAssert.cs" />
-    <Compile Include="NullableAttributes.cs" />
     <Compile Include="OutputHelper.cs" />
     <Compile Include="TestExtensions.cs" />
   </ItemGroup>