Add some System.Runtime.InteropServices tests (#21140)

* Cleanup some product code

* Cleanup and bolster existing tests

25 files changed, 322 insertions, 318 deletions

diff --git a/src/System.Runtime.InteropServices/src/System/Runtime/CompilerServices/Attributes.cs b/src/System.Runtime.InteropServices/src/System/Runtime/CompilerServices/Attributes.cs
index 6ccbc1c304..e98f40d317 100644
--- a/src/System.Runtime.InteropServices/src/System/Runtime/CompilerServices/Attributes.cs
+++ b/src/System.Runtime.InteropServices/src/System/Runtime/CompilerServices/Attributes.cs
@@ -7,15 +7,10 @@ using System.Runtime.InteropServices;
 namespace System.Runtime.CompilerServices
 {
     [System.AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter, Inherited = false)]
-    public sealed partial class IUnknownConstantAttribute : System.Runtime.CompilerServices.CustomConstantAttribute
+    public sealed partial class IUnknownConstantAttribute : CustomConstantAttribute
     {
         public IUnknownConstantAttribute() { }
-        public override object Value
-        {
-            get
-            {
-                return new UnknownWrapper(null);
-            }
-        }
+
+        public override object Value => new UnknownWrapper(null);
     }
 }
diff --git a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/Attributes.cs b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/Attributes.cs
index af989d0742..9ab87e0ca3 100644
--- a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/Attributes.cs
+++ b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/Attributes.cs
@@ -2,27 +2,21 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-
 namespace System.Runtime.InteropServices
 {
     [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Interface, Inherited = false)]
     public sealed class AutomationProxyAttribute : Attribute
     {
-        public AutomationProxyAttribute(bool val)
-        {
-            Value = val;
-        }
+        public AutomationProxyAttribute(bool val) => Value = val;
+
         public bool Value { get; }
     }
 
     [AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Field | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
     public sealed class ComAliasNameAttribute : Attribute
     {
-        public ComAliasNameAttribute(string alias)
-        {
-            Value = alias;
-        }
+        public ComAliasNameAttribute(string alias) => Value = alias;
+
         public string Value { get; }
     }
 
@@ -62,14 +56,12 @@ namespace System.Runtime.InteropServices
     [Obsolete("This attribute is deprecated and will be removed in a future version.", false)]
     public sealed class IDispatchImplAttribute : Attribute
     {
-        public IDispatchImplAttribute(short implType)
-        {
-            Value = (IDispatchImplType)implType;
-        }
-        public IDispatchImplAttribute(IDispatchImplType implType)
+        public IDispatchImplAttribute(short implType) : this((IDispatchImplType)implType)
         {
-            Value = implType;
         }
+
+        public IDispatchImplAttribute(IDispatchImplType implType) => Value = implType;
+
         public IDispatchImplType Value { get; }
     }
 
@@ -84,10 +76,8 @@ namespace System.Runtime.InteropServices
     [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
     public sealed class ImportedFromTypeLibAttribute : Attribute
     {
-        public ImportedFromTypeLibAttribute(String tlbFile)
-        {
-            Value = tlbFile;
-        }
+        public ImportedFromTypeLibAttribute(string tlbFile) => Value = tlbFile;
+
         public string Value { get; }
     }
 
@@ -129,10 +119,8 @@ namespace System.Runtime.InteropServices
     [AttributeUsage(AttributeTargets.Interface, Inherited = false)]
     public sealed class TypeLibImportClassAttribute : Attribute
     {
-        public TypeLibImportClassAttribute(Type importClass)
-        {
-            Value = importClass.ToString();
-        }
+        public TypeLibImportClassAttribute(Type importClass) => Value = importClass.ToString();
+
         public string Value { get; }
     }
 
@@ -192,16 +180,18 @@ namespace System.Runtime.InteropServices
     }
 
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface | AttributeTargets.Enum | AttributeTargets.Struct, Inherited = false)]
-    public sealed class  TypeLibTypeAttribute : Attribute
+    public sealed class TypeLibTypeAttribute : Attribute
     {
         public TypeLibTypeAttribute(TypeLibTypeFlags flags)
         {
             Value = flags;
         }
+
         public TypeLibTypeAttribute(short flags)
         {
             Value = (TypeLibTypeFlags)flags;
         }
+
         public TypeLibTypeFlags Value { get; }
     }
 
@@ -212,10 +202,12 @@ namespace System.Runtime.InteropServices
         {
             Value = flags;
         }
+
         public TypeLibFuncAttribute(short flags)
         {
             Value = (TypeLibFuncFlags)flags;
         }
+
         public TypeLibFuncFlags Value { get; }
     }
 
@@ -226,15 +218,17 @@ namespace System.Runtime.InteropServices
         {
             Value = flags;
         }
+
         public TypeLibVarAttribute(short flags)
         {
             Value = (TypeLibVarFlags)flags;
         }
+
         public TypeLibVarFlags Value { get; }
     }
 
     [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
-    [System.Runtime.InteropServices.ComVisible(true)]
+    [ComVisible(true)]
     public sealed class TypeLibVersionAttribute : Attribute
     {
         public TypeLibVersionAttribute(int major, int minor)
diff --git a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/ComAwareEventInfo.cs b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/ComAwareEventInfo.cs
index f5fac0b579..6212d0b62f 100644
--- a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/ComAwareEventInfo.cs
+++ b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/ComAwareEventInfo.cs
@@ -2,28 +2,29 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Reflection;
+using System.Security;
+
 namespace System.Runtime.InteropServices
 {
-    [System.Security.SecuritySafeCritical]
-    public class ComAwareEventInfo : System.Reflection.EventInfo
+    [SecuritySafeCritical]
+    public class ComAwareEventInfo : EventInfo
     {
-        private System.Reflection.EventInfo _innerEventInfo;
+        private EventInfo _innerEventInfo;
 
         public ComAwareEventInfo(Type type, string eventName)
         {
             _innerEventInfo = type.GetEvent(eventName);
         }
 
-        [System.Security.SecuritySafeCritical]
+        [SecuritySafeCritical]
         public override void AddEventHandler(object target, Delegate handler)
         {
             if (Marshal.IsComObject(target))
             {
                 // retrieve sourceIid and dispid
-                Guid sourceIid;
-                int dispid;
-                GetDataForComInvocation(_innerEventInfo, out sourceIid, out dispid);
-                System.Runtime.InteropServices.ComEventsHelper.Combine(target, sourceIid, dispid, handler);
+                GetDataForComInvocation(_innerEventInfo, out Guid sourceIid, out int dispid);
+                ComEventsHelper.Combine(target, sourceIid, dispid, handler);
             }
             else
             {
@@ -32,17 +33,15 @@ namespace System.Runtime.InteropServices
             }
         }
 
-        [System.Security.SecuritySafeCritical]
+        [SecuritySafeCritical]
         public override void RemoveEventHandler(object target, Delegate handler)
         {
             if (Marshal.IsComObject(target))
             {
                 // retrieve sourceIid and dispid
-                Guid sourceIid;
-                int dispid;
-                GetDataForComInvocation(_innerEventInfo, out sourceIid, out dispid);
+                GetDataForComInvocation(_innerEventInfo, out Guid sourceIid, out int dispid);
 
-                System.Runtime.InteropServices.ComEventsHelper.Remove(target, sourceIid, dispid, handler);
+                ComEventsHelper.Remove(target, sourceIid, dispid, handler);
             }
             else
             {
@@ -51,30 +50,15 @@ namespace System.Runtime.InteropServices
             }
         }
 
-        public override System.Reflection.EventAttributes Attributes
-        {
-            get { return _innerEventInfo.Attributes; }
-        }
+        public override EventAttributes Attributes => _innerEventInfo.Attributes;
 
-        public override System.Reflection.MethodInfo GetAddMethod(bool nonPublic)
-        {
-            return _innerEventInfo.GetAddMethod(nonPublic);
-        }
+        public override MethodInfo GetAddMethod(bool nonPublic) => _innerEventInfo.GetAddMethod(nonPublic);
 
-        public override System.Reflection.MethodInfo GetRaiseMethod(bool nonPublic)
-        {
-            return _innerEventInfo.GetRaiseMethod(nonPublic);
-        }
+        public override MethodInfo GetRaiseMethod(bool nonPublic) => _innerEventInfo.GetRaiseMethod(nonPublic);
 
-        public override System.Reflection.MethodInfo GetRemoveMethod(bool nonPublic)
-        {
-            return _innerEventInfo.GetRemoveMethod(nonPublic);
-        }
+        public override MethodInfo GetRemoveMethod(bool nonPublic) => _innerEventInfo.GetRemoveMethod(nonPublic);
 
-        public override Type DeclaringType
-        {
-            get { return _innerEventInfo.DeclaringType; }
-        }
+        public override Type DeclaringType => _innerEventInfo.DeclaringType;
 
         public override object[] GetCustomAttributes(Type attributeType, bool inherit)
         {
@@ -91,15 +75,9 @@ namespace System.Runtime.InteropServices
             return _innerEventInfo.IsDefined(attributeType, inherit);
         }
 
-        public override string Name
-        {
-            get { return _innerEventInfo.Name; }
-        }
+        public override string Name => _innerEventInfo.Name;
 
-        public override Type ReflectedType
-        {
-            get { return _innerEventInfo.ReflectedType; }
-        }
+        public override Type ReflectedType => _innerEventInfo.ReflectedType;
 
         private static void GetDataForComInvocation(System.Reflection.EventInfo eventInfo, out Guid sourceIid, out int dispid)
         {
@@ -114,13 +92,13 @@ namespace System.Runtime.InteropServices
             if (comEventInterfaces.Length > 1)
             {
                 // TODO: event strings need to be localizable
-                throw new System.Reflection.AmbiguousMatchException("more than one ComSourceInterfaceGuidAttribute found");
+                throw new AmbiguousMatchException("more than one ComSourceInterfaceGuidAttribute found");
             }
 
             Type sourceItf = ((ComEventInterfaceAttribute)comEventInterfaces[0]).SourceInterface;
             Guid guid = sourceItf.GUID;
 
-            System.Reflection.MethodInfo methodInfo = sourceItf.GetMethod(eventInfo.Name);
+            MethodInfo methodInfo = sourceItf.GetMethod(eventInfo.Name);
             Attribute dispIdAttribute = Attribute.GetCustomAttribute(methodInfo, typeof(DispIdAttribute));
             if (dispIdAttribute == null)
             {
diff --git a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/ComEventInterfaceAttribute.cs b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/ComEventInterfaceAttribute.cs
index 7cb6fb951e..3a3cef7c4e 100644
--- a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/ComEventInterfaceAttribute.cs
+++ b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/ComEventInterfaceAttribute.cs
@@ -2,23 +2,18 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-
 namespace System.Runtime.InteropServices
 {
     [AttributeUsage(AttributeTargets.Interface, Inherited = false)]
     public sealed class ComEventInterfaceAttribute : Attribute
     {
-        internal Type _SourceInterface;
-        internal Type _EventProvider;
-
         public ComEventInterfaceAttribute(Type SourceInterface, Type EventProvider)
         {
-            _SourceInterface = SourceInterface;
-            _EventProvider = EventProvider;
+            this.SourceInterface = SourceInterface;
+            this.EventProvider = EventProvider;
         }
 
-        public Type SourceInterface { get { return _SourceInterface; } }
-        public Type EventProvider { get { return _EventProvider; } }
+        public Type SourceInterface { get; }
+        public Type EventProvider { get; }
     }
 }
\ No newline at end of file
diff --git a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/DefaultParameterValueAttribute.cs b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/DefaultParameterValueAttribute.cs
index 6b50bd148d..160a961790 100644
--- a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/DefaultParameterValueAttribute.cs
+++ b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/DefaultParameterValueAttribute.cs
@@ -10,16 +10,11 @@ namespace System.Runtime.InteropServices
     // from other languages. This is particularly useful for 
     // methods defined in COM interop interfaces.
     //
-    [AttributeUsageAttribute(AttributeTargets.Parameter)]
+    [AttributeUsage(AttributeTargets.Parameter)]
     public sealed class DefaultParameterValueAttribute : Attribute
     {
-        public DefaultParameterValueAttribute(object value)
-        {
-            _value = value;
-        }
+        public DefaultParameterValueAttribute(object value) => Value = value;
 
-        public object Value { get { return _value; } }
-
-        private object _value;
+        public object Value { get; }
     }
 }
diff --git a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/HandleCollector.cs b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/HandleCollector.cs
index 2dea85f3af..49eba3b952 100644
--- a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/HandleCollector.cs
+++ b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/HandleCollector.cs
@@ -8,10 +8,8 @@ namespace System.Runtime.InteropServices
 {
     public sealed class HandleCollector
     {
-        private const int deltaPercent = 10; // this is used for increasing the threshold.        
-        private string _name;
+        private const int DeltaPercent = 10; // this is used for increasing the threshold. 
         private int _initialThreshold;
-        private int _maximumThreshold;
         private int _threshold;
         private int _handleCount;
 
@@ -40,28 +38,20 @@ namespace System.Runtime.InteropServices
                 throw new ArgumentException(SR.Arg_InvalidThreshold);
             }
 
-            if (name != null)
-            {
-                _name = name;
-            }
-            else
-            {
-                _name = String.Empty;
-            }
-
+            Name = name ?? string.Empty;
             _initialThreshold = initialThreshold;
-            _maximumThreshold = maximumThreshold;
+            MaximumThreshold = maximumThreshold;
             _threshold = initialThreshold;
             _handleCount = 0;
         }
 
-        public int Count { get { return _handleCount; } }
+        public int Count => _handleCount;
 
-        public int InitialThreshold { get { return _initialThreshold; } }
+        public int InitialThreshold => _initialThreshold;
 
-        public int MaximumThreshold { get { return _maximumThreshold; } }
+        public int MaximumThreshold { get; }
 
-        public string Name { get { return _name; } }
+        public string Name { get; }
 
         public void Add()
         {
@@ -76,7 +66,7 @@ namespace System.Runtime.InteropServices
             {
                 lock (this)
                 {
-                    _threshold = _handleCount + (_handleCount / deltaPercent);
+                    _threshold = _handleCount + (_handleCount / DeltaPercent);
                     gen_collect = _gc_gen;
                     if (_gc_gen < 2)
                     {
@@ -108,8 +98,8 @@ namespace System.Runtime.InteropServices
                 throw new InvalidOperationException(SR.InvalidOperation_HCCountOverflow);
             }
 
-            int newThreshold = _handleCount + _handleCount / deltaPercent;
-            if (newThreshold < (_threshold - _threshold / deltaPercent))
+            int newThreshold = _handleCount + _handleCount / DeltaPercent;
+            if (newThreshold < (_threshold - _threshold / DeltaPercent))
             {
                 lock (this)
                 {
diff --git a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/RuntimeEnvironment.cs b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/RuntimeEnvironment.cs
index 57f0837ee3..b68f90baf5 100644
--- a/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/RuntimeEnvironment.cs
+++ b/src/System.Runtime.InteropServices/src/System/Runtime/InteropServices/RuntimeEnvironment.cs
@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.IO;
 using System.Reflection;
 
@@ -10,17 +9,10 @@ namespace System.Runtime.InteropServices
 {
     public static class RuntimeEnvironment
     {
-        public static string SystemConfigurationFile
-        {
-            get
-            {
-                throw new PlatformNotSupportedException();
-            }
-        }
-        public static bool FromGlobalAccessCache(System.Reflection.Assembly a)
-        {
-            return false;
-        }
+        public static string SystemConfigurationFile => throw new PlatformNotSupportedException();
+
+        public static bool FromGlobalAccessCache(Assembly a) => false;
+
         public static string GetRuntimeDirectory()
         {
             string runtimeDirectory = typeof(object).Assembly.Location;
@@ -30,17 +22,11 @@ namespace System.Runtime.InteropServices
             }
             return Path.GetDirectoryName(runtimeDirectory) + Path.DirectorySeparatorChar;
         }
-        public static System.IntPtr GetRuntimeInterfaceAsIntPtr(Guid clsid, Guid riid)
-        {
-            throw new PlatformNotSupportedException();
-        }
-        public static object GetRuntimeInterfaceAsObject(Guid clsid, Guid riid)
-        {
-            throw new PlatformNotSupportedException();
-        }
-        public static string GetSystemVersion()
-        {
-            return typeof(object).Assembly.ImageRuntimeVersion;
-        }
+
+        public static IntPtr GetRuntimeInterfaceAsIntPtr(Guid clsid, Guid riid) => throw new PlatformNotSupportedException();
+
+        public static object GetRuntimeInterfaceAsObject(Guid clsid, Guid riid) => throw new PlatformNotSupportedException();
+
+        public static string GetSystemVersion() => typeof(object).Assembly.ImageRuntimeVersion;
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System.Runtime.InteropServices.Tests.csproj b/src/System.Runtime.InteropServices/tests/System.Runtime.InteropServices.Tests.csproj
index 5d13a5b16a..a43afc32dc 100644
--- a/src/System.Runtime.InteropServices/tests/System.Runtime.InteropServices.Tests.csproj
+++ b/src/System.Runtime.InteropServices/tests/System.Runtime.InteropServices.Tests.csproj
@@ -18,7 +18,6 @@
     <Compile Include="$(CommonTestPath)\System\PlatformDetection.cs">
       <Link>Common\System\PlatformDetection.cs</Link>
     </Compile>
-    <Compile Include="System\Runtime\InteropServices\RuntimeEnvironmentTest.cs" />
     <Compile Include="System\Runtime\InteropServices\AllowReversePInvokeCallsAttributeTests.cs" />
     <Compile Include="System\Runtime\InteropServices\CallingConventionTests.cs" />
     <Compile Include="System\Runtime\InteropServices\ComAliasNameAttributeTests.cs" />
@@ -31,6 +30,10 @@
     <Compile Include="System\Runtime\InteropServices\LCIDConversionAttributeTests.cs" />
     <Compile Include="System\Runtime\InteropServices\PrimaryInteropAssemblyAttributeTests.cs" />
     <Compile Include="System\Runtime\InteropServices\ProgIdAttributeTests.cs" />
+    <Compile Include="System\Runtime\InteropServices\RuntimeEnvironmentTests.cs" />
+    <Compile Include="$(CommonTestPath)\System\AssertExtensions.cs">
+      <Link>Common\System\AssertExtensions.cs</Link>
+    </Compile>
     <Compile Include="$(CommonTestPath)\System\Runtime\Serialization\Formatters\BinaryFormatterHelpers.cs">
       <Link>System\Runtime\Serialization\Formatters\BinaryFormatterHelpers.cs</Link>
     </Compile>
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/AllowReversePInvokeCallsAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/AllowReversePInvokeCallsAttributeTests.cs
index 1d71e986e5..08a65e7a13 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/AllowReversePInvokeCallsAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/AllowReversePInvokeCallsAttributeTests.cs
@@ -11,18 +11,15 @@ namespace System.Runtime.InteropServices.Tests
     public class AllowReversePInvokeCallsAttributeTests
     {
         [AllowReversePInvokeCalls]
-        private int Func(int a, int b)
-        {
-            return a + b;
-        }
+        private int Func(int a, int b) => a + b;
 
         [Fact]
         public void Exists()
         {
-            var type = typeof(AllowReversePInvokeCallsAttributeTests);
-            var method = type.GetTypeInfo().DeclaredMethods.Single(m => m.Name == "Func");
-            var attr = method.GetCustomAttributes(typeof(AllowReversePInvokeCallsAttribute), false).OfType<AllowReversePInvokeCallsAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
+            Type type = typeof(AllowReversePInvokeCallsAttributeTests);
+            MethodInfo method = type.GetTypeInfo().DeclaredMethods.Single(m => m.Name == "Func");
+            AllowReversePInvokeCallsAttribute attribute = Assert.Single(method.GetCustomAttributes< AllowReversePInvokeCallsAttribute>(false));
+            Assert.NotNull(attribute);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/CallingConventionTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/CallingConventionTests.cs
index 7ea53a1e2b..63df4f90dc 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/CallingConventionTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/CallingConventionTests.cs
@@ -2,22 +2,21 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Linq;
-using System.Reflection;
 using Xunit;
 
 namespace System.Runtime.InteropServices.Tests
 {
     public class CallingConventionTests
     {
-        [Fact]
-        public void Values()
+        [Theory]
+        [InlineData(CallingConvention.Winapi, 1)]
+        [InlineData(CallingConvention.Cdecl, 2)]
+        [InlineData(CallingConvention.StdCall, 3)]
+        [InlineData(CallingConvention.ThisCall, 4)]
+        [InlineData(CallingConvention.FastCall, 5)]
+        public void CallingConvention_Get_ReturnsExpected(CallingConvention convention, int expected)
         {
-            Assert.Equal(1, (int)CallingConvention.Winapi);
-            Assert.Equal(2, (int)CallingConvention.Cdecl);
-            Assert.Equal(3, (int)CallingConvention.StdCall);
-            Assert.Equal(4, (int)CallingConvention.ThisCall);
-            Assert.Equal(5, (int)CallingConvention.FastCall);
+            Assert.Equal(expected, (int)convention);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComAliasNameAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComAliasNameAttributeTests.cs
index 88ad06210a..4fef851968 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComAliasNameAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComAliasNameAttributeTests.cs
@@ -18,11 +18,19 @@ namespace System.Runtime.InteropServices.Tests
         [Fact]
         public void Exists()
         {
-            var type = typeof(ComAliasNameAttributeTests);
-            var field = type.GetTypeInfo().DeclaredFields.Single(f => f.Name == "_foo");
-            var attr = field.GetCustomAttributes(typeof(ComAliasNameAttribute), false).OfType<ComAliasNameAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
-            Assert.Equal("foo", attr.Value);
+            FieldInfo field = typeof(ComAliasNameAttributeTests).GetTypeInfo().DeclaredFields.Single(f => f.Name == "_foo");
+            ComAliasNameAttribute attribute = Assert.Single(field.GetCustomAttributes<ComAliasNameAttribute>(false));
+            Assert.Equal("foo", attribute.Value);
+        }
+
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        [InlineData("value")]
+        public void Ctor_Alias(string alias)
+        {
+            var attribute = new ComAliasNameAttribute(alias);
+            Assert.Equal(alias, attribute.Value);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComCompatibleVersionAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComCompatibleVersionAttributeTests.cs
index 6545abba7b..695f80ad1b 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComCompatibleVersionAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComCompatibleVersionAttributeTests.cs
@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Linq;
 using System.Reflection;
 using System.Runtime.InteropServices;
 using Xunit;
@@ -16,14 +15,26 @@ namespace System.Runtime.InteropServices.Tests
         [Fact]
         public void Exists()
         {
-            var type = typeof(ComCompatibleVersionAttributeTests);
-            var assembly = type.GetTypeInfo().Assembly;
-            var attr = assembly.GetCustomAttributes(typeof(ComCompatibleVersionAttribute), false).OfType<ComCompatibleVersionAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
-            Assert.Equal(1, attr.MajorVersion);
-            Assert.Equal(2, attr.MinorVersion);
-            Assert.Equal(3, attr.BuildNumber);
-            Assert.Equal(4, attr.RevisionNumber);
+            Type type = typeof(ComCompatibleVersionAttributeTests);
+            Assembly assembly = type.GetTypeInfo().Assembly;
+            ComCompatibleVersionAttribute attribute = Assert.Single(assembly.GetCustomAttributes<ComCompatibleVersionAttribute>());
+            Assert.Equal(1, attribute.MajorVersion);
+            Assert.Equal(2, attribute.MinorVersion);
+            Assert.Equal(3, attribute.BuildNumber);
+            Assert.Equal(4, attribute.RevisionNumber);
+        }
+
+        [Theory]
+        [InlineData(-1, -2, -3, -4)]
+        [InlineData(0, 0, 0, 0)]
+        [InlineData(1, 2, 3, 4)]
+        public void Ctor_Major_Minor_Build_Revision(int major, int minor, int build, int revision)
+        {
+            var attribute = new ComCompatibleVersionAttribute(major, minor, build, revision);
+            Assert.Equal(major, attribute.MajorVersion);
+            Assert.Equal(minor, attribute.MinorVersion);
+            Assert.Equal(build, attribute.BuildNumber);
+            Assert.Equal(revision, attribute.RevisionNumber);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComConversionLossAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComConversionLossAttributeTests.cs
index a723f49257..07871ad859 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComConversionLossAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComConversionLossAttributeTests.cs
@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Linq;
-using System.Reflection;
 using Xunit;
 
 namespace System.Runtime.InteropServices.Tests
@@ -14,9 +12,9 @@ namespace System.Runtime.InteropServices.Tests
         [Fact]
         public void Exists()
         {
-            var type = typeof(ComConversionLossAttributeTests);
-            var attr = type.GetCustomAttributes(typeof(ComConversionLossAttribute), false).OfType<ComConversionLossAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
+            Type type = typeof(ComConversionLossAttributeTests);
+            ComConversionLossAttribute attribute = Assert.IsType<ComConversionLossAttribute>(Assert.Single(type.GetCustomAttributes(typeof(ComConversionLossAttribute), false)));
+            Assert.NotNull(attribute);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComRegisterFunctionAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComRegisterFunctionAttributeTests.cs
index fbc4332026..0d4c40ba65 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComRegisterFunctionAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComRegisterFunctionAttributeTests.cs
@@ -11,18 +11,15 @@ namespace System.Runtime.InteropServices.Tests
     public class ComRegisterFunctionAttributeTests
     {
         [ComRegisterFunction]
-        private int Func(int a, int b)
-        {
-            return a + b;
-        }
+        private int Func(int a, int b) => a + b;
 
         [Fact]
         public void Exists()
         {
-            var type = typeof(ComRegisterFunctionAttributeTests);
-            var method = type.GetTypeInfo().DeclaredMethods.Single(m => m.Name == "Func");
-            var attr = method.GetCustomAttributes(typeof(ComRegisterFunctionAttribute), false).OfType<ComRegisterFunctionAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
+            Type type = typeof(ComRegisterFunctionAttributeTests);
+            MethodInfo method = type.GetTypeInfo().DeclaredMethods.Single(m => m.Name == "Func");
+            ComRegisterFunctionAttribute attribute = Assert.Single(method.GetCustomAttributes<ComRegisterFunctionAttribute>(false));
+            Assert.NotNull(attribute);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComUnregisterFunctionAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComUnregisterFunctionAttributeTests.cs
index 3189d93e69..80d37d15f8 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComUnregisterFunctionAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComUnregisterFunctionAttributeTests.cs
@@ -11,18 +11,15 @@ namespace System.Runtime.InteropServices.Tests
     public class ComUnregisterFunctionAttributeTests
     {
         [ComUnregisterFunction]
-        private int Func(int a, int b)
-        {
-            return a + b;
-        }
+        private int Func(int a, int b) => a + b;
 
         [Fact]
         public void Exists()
         {
-            var type = typeof(ComUnregisterFunctionAttributeTests);
-            var method = type.GetTypeInfo().DeclaredMethods.Single(m => m.Name == "Func");
-            var attr = method.GetCustomAttributes(typeof(ComUnregisterFunctionAttribute), false).OfType<ComUnregisterFunctionAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
+            Type type = typeof(ComUnregisterFunctionAttributeTests);
+            MethodInfo method = type.GetTypeInfo().DeclaredMethods.Single(m => m.Name == "Func");
+            ComUnregisterFunctionAttribute attribute = Assert.Single(method.GetCustomAttributes<ComUnregisterFunctionAttribute>(false));
+            Assert.NotNull(attribute);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComVisibleAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComVisibleAttributeTests.cs
index 6c0124ad00..b7c0814672 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComVisibleAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ComVisibleAttributeTests.cs
@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Linq;
-using System.Reflection;
 using Xunit;
 
 namespace System.Runtime.InteropServices.Tests
@@ -14,10 +12,18 @@ namespace System.Runtime.InteropServices.Tests
         [Fact]
         public void Exists()
         {
-            var type = typeof(ComVisibleAttributeTests);
-            var attr = type.GetCustomAttributes(typeof(ComVisibleAttribute), false).OfType<ComVisibleAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
-            Assert.Equal(true, attr.Value);
+            Type type = typeof(ComVisibleAttributeTests);
+            ComVisibleAttribute attribute = Assert.IsType<ComVisibleAttribute>(Assert.Single(type.GetCustomAttributes(typeof(ComVisibleAttribute), false)));
+            Assert.True(attribute.Value);
+        }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Ctor_Visible(bool visibility)
+        {
+            var attribute = new ComVisibleAttribute(visibility);
+            Assert.Equal(visibility, attribute.Value);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/DefaultParameterValueAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/DefaultParameterValueAttributeTests.cs
index 97f568deb5..fa2ac4bdf6 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/DefaultParameterValueAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/DefaultParameterValueAttributeTests.cs
@@ -15,10 +15,10 @@ namespace System.Runtime.InteropServices
         [InlineData(5.0f)]
         [InlineData("ExpectedValue")]
         [InlineData(null)]
-        public static void Constructor(object expected)
+        public static void Ctor_Value(object value)
         {
-            DefaultParameterValueAttribute attribute = new DefaultParameterValueAttribute(expected);
-            Assert.Equal(expected, attribute.Value);
+            var attribute = new DefaultParameterValueAttribute(value);
+            Assert.Equal(value, attribute.Value);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/HandleCollectorTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/HandleCollectorTests.cs
index 4c73dd4244..d67005548d 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/HandleCollectorTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/HandleCollectorTests.cs
@@ -7,53 +7,81 @@ using Xunit;
 
 namespace System.Runtime.InteropServices
 {
-    public static class HandleCollectorTests
+    public class HandleCollectorTests
     {
         private const int LowLimitSize = 20;
         private const int HighLimitSize = 100000;
 
-        [Fact]
-        public static void NegativeInitialThresholdCtor()
+        [Theory]
+        [InlineData(null, 0)]
+        [InlineData("", 10)]
+        [InlineData("InitialThreshold", int.MaxValue)]
+        public void Ctor_Name_InitialThreshold(string name, int initialThreshold)
         {
-            Assert.Throws<ArgumentOutOfRangeException>(() => new HandleCollector("NegativeInitial", -1));
+            var handleCollector = new HandleCollector(name, initialThreshold);
+            Assert.Equal(0, handleCollector.Count);
+            Assert.Equal(name ?? string.Empty, handleCollector.Name);
+            Assert.Equal(initialThreshold, handleCollector.InitialThreshold);
+            Assert.Equal(int.MaxValue, handleCollector.MaximumThreshold);
         }
 
-        [Fact]
-        public static void NegateMaximumThresholdCtor()
+        [Theory]
+        [InlineData(null, 0, 0)]
+        [InlineData("", 10, 15)]
+        [InlineData("InitialThreshold", 1, 2)]
+        public void Ctor_Name_InitialThreshold_MaximumThreshold(string name, int initialThreshold, int maximumThreshold)
         {
-            Assert.Throws<ArgumentOutOfRangeException>(() => new HandleCollector("NegativeMax", 0, -1));
+            var handleCollector = new HandleCollector(name, initialThreshold, maximumThreshold);
+            Assert.Equal(0, handleCollector.Count);
+            Assert.Equal(name ?? string.Empty, handleCollector.Name);
+            Assert.Equal(initialThreshold, handleCollector.InitialThreshold);
+            Assert.Equal(maximumThreshold, handleCollector.MaximumThreshold);
         }
 
         [Fact]
-        public static void InitialGreaterThanMaxThresholdCtor()
+        public void Ctor_NegativeInitialThreshold_ThrowsArgumentOufORangeException()
         {
-            Assert.Throws<ArgumentException>(() => new HandleCollector("InitialGreaterThanMax", 100, 1));
+            AssertExtensions.Throws<ArgumentOutOfRangeException>("initialThreshold", () => new HandleCollector("NegativeInitial", -1));
+            AssertExtensions.Throws<ArgumentOutOfRangeException>("initialThreshold", () => new HandleCollector("NegativeInitial", -1, 0));
         }
 
         [Fact]
-        public static void SimplePropertyValidation()
+        public static void Ctor_NegativeMaximumThreshold_ThrowsArgumentOutOfRangeException()
         {
-            string name = "ExampleName";
-            int initial = 10;
-            int max = 20;
-
-            HandleCollector collector = new HandleCollector(name, initial, max);
+            AssertExtensions.Throws<ArgumentOutOfRangeException>("maximumThreshold", () => new HandleCollector("NegativeMax", 0, -1));
+        }
 
-            Assert.Equal(0, collector.Count);
-            Assert.Equal(name, collector.Name);
-            Assert.Equal(initial, collector.InitialThreshold);
-            Assert.Equal(max, collector.MaximumThreshold);
+        [Fact]
+        public static void Ctor_InitialThresholdGreaterThanMaximumThreshold_ThrowsArgumentException()
+        {
+            AssertExtensions.Throws<ArgumentException>(null, () => new HandleCollector("InitialGreaterThanMax", 100, 1));
         }
 
         [Fact]
-        public static void NullNameCtor()
+        public void AddRemove_AcrossMultipleGenerations_Success()
         {
-            HandleCollector collector = new HandleCollector(null, 0, 0);
-            Assert.Equal(string.Empty, collector.Name);
+            var collector = new HandleCollector("name", 0);
+            collector.Add();
+            Assert.Equal(1, collector.Count);
+
+            collector.Add();
+            Assert.Equal(2, collector.Count);
+
+            collector.Add();
+            Assert.Equal(3, collector.Count);
+
+            collector.Remove();
+            Assert.Equal(2, collector.Count);
+
+            collector.Remove();
+            Assert.Equal(1, collector.Count);
+
+            collector.Remove();
+            Assert.Equal(0, collector.Count);
         }
 
         [Fact]
-        public static void EmptyRemoval()
+        public static void Remove_EmptyCollection_ThrowsInvalidOperationException()
         {
             HandleCollector collector = new HandleCollector("EmptyRemoval", 10);
             Assert.Throws<InvalidOperationException>(() => collector.Remove());
@@ -61,7 +89,7 @@ namespace System.Runtime.InteropServices
 
         [Fact]
         [SkipOnTargetFramework(TargetFrameworkMonikers.UapAot,"Reflects on private member handleCount")]
-        public static void CountOverflow()
+        public static void Add_Overflows_ThrowsInvalidOperationException()
         {
             HandleCollector collector = new HandleCollector("CountOverflow", int.MaxValue);
 
@@ -95,10 +123,7 @@ namespace System.Runtime.InteropServices
         [Fact]
         public static void TestHandleCollector()
         {
-            Tuple<int, int, int> initialGcState = new Tuple<int, int, int>(
-                GC.CollectionCount(0),
-                GC.CollectionCount(1),
-                GC.CollectionCount(2));
+            (int gen0, int gen1, int gen2) initialGcState = (GC.CollectionCount(0), GC.CollectionCount(1), GC.CollectionCount(2));
 
             HandleCollector lowLimitCollector = new HandleCollector("LowLimit.Collector", LowLimitSize);
             for (int i = 0; i < LowLimitSize + 1; ++i)
@@ -106,12 +131,9 @@ namespace System.Runtime.InteropServices
                 HandleLimitTester hlt = new HandleLimitTester(lowLimitCollector);
             }
 
-            Tuple<int, int, int> postLowLimitState = new Tuple<int, int, int>(
-                GC.CollectionCount(0),
-                GC.CollectionCount(1),
-                GC.CollectionCount(2));
+            (int gen0, int gen1, int gen2) postLowLimitState = (GC.CollectionCount(0),GC.CollectionCount(1), GC.CollectionCount(2));
 
-            Assert.True(initialGcState.Item1 + initialGcState.Item2 + initialGcState.Item3 < postLowLimitState.Item1 + postLowLimitState.Item2 + postLowLimitState.Item3, "Low limit handle did not trigger a GC");
+            Assert.True(initialGcState.gen0 + initialGcState.gen1 + initialGcState.gen2 < postLowLimitState.gen0 + postLowLimitState.gen1 + postLowLimitState.gen2, "Low limit handle did not trigger a GC");
 
             HandleCollector highLimitCollector = new HandleCollector("HighLimit.Collector", HighLimitSize);
             for (int i = 0; i < HighLimitSize + 10; ++i)
@@ -119,12 +141,9 @@ namespace System.Runtime.InteropServices
                 HandleLimitTester hlt = new HandleLimitTester(highLimitCollector);
             }
 
-            Tuple<int, int, int> postHighLimitState = new Tuple<int, int, int>(
-                GC.CollectionCount(0),
-                GC.CollectionCount(1),
-                GC.CollectionCount(2));
+            (int gen0, int gen1, int gen2) postHighLimitState = (GC.CollectionCount(0), GC.CollectionCount(1), GC.CollectionCount(2));
 
-            Assert.True(postLowLimitState.Item1 + postLowLimitState.Item2 + postLowLimitState.Item3 < postHighLimitState.Item1 + postHighLimitState.Item2 + postHighLimitState.Item3, "High limit handle did not trigger a GC");
+            Assert.True(postLowLimitState.gen0 + postLowLimitState.gen1 + postLowLimitState.gen2 < postHighLimitState.gen0 + postHighLimitState.gen1 + postHighLimitState.gen2, "High limit handle did not trigger a GC");
         }
 
         private sealed class HandleLimitTester
@@ -138,10 +157,7 @@ namespace System.Runtime.InteropServices
                 GC.KeepAlive(this);
             }
 
-            ~HandleLimitTester()
-            {
-                _collector.Remove();
-            }
+            ~HandleLimitTester() => _collector.Remove();
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/HandleRefTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/HandleRefTests.cs
index 8f1979e262..9183dcd010 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/HandleRefTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/HandleRefTests.cs
@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Linq;
-using System.Reflection;
 using Xunit;
 
 namespace System.Runtime.InteropServices.Tests
@@ -11,15 +9,25 @@ namespace System.Runtime.InteropServices.Tests
     public class HandleRefTests
     {
         [Fact]
-        public void Properties()
+        public void Ctor_Default()
         {
-            var obj = new object();
-            var ptr = new IntPtr(1337);
-            var handleRef = new HandleRef(obj, ptr);
-            Assert.Equal(ptr, (IntPtr)handleRef);
-            Assert.Equal(ptr, HandleRef.ToIntPtr(handleRef));
-            Assert.Equal(ptr, handleRef.Handle);
-            Assert.Same(obj, handleRef.Wrapper);
+            var handleRef = new HandleRef();
+            Assert.Null(handleRef.Wrapper);
+            Assert.Equal(IntPtr.Zero, handleRef.Handle);
+            Assert.Equal(IntPtr.Zero, (IntPtr)handleRef);
+            Assert.Equal(IntPtr.Zero, HandleRef.ToIntPtr(handleRef));
+        }
+
+        [Theory]
+        [InlineData(null, 0)]
+        [InlineData("Wrapper", 1337)]
+        public void Ctor_Wrapper_Handle(object wrapper, int handle)
+        {
+            var handleRef = new HandleRef(wrapper, (IntPtr)handle);
+            Assert.Same(wrapper, handleRef.Wrapper);
+            Assert.Equal((IntPtr)handle, handleRef.Handle);
+            Assert.Equal((IntPtr)handle, (IntPtr)handleRef);
+            Assert.Equal((IntPtr)handle, HandleRef.ToIntPtr(handleRef));
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/LCIDConversionAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/LCIDConversionAttributeTests.cs
index 48198b04e8..cc5dd2c080 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/LCIDConversionAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/LCIDConversionAttributeTests.cs
@@ -11,19 +11,25 @@ namespace System.Runtime.InteropServices.Tests
     public class LCIDConversionAttributeTests
     {
         [LCIDConversion(1337)]
-        private int Func(int a, int b)
-        {
-            return a + b;
-        }
+        private int Func(int a, int b) => a + b;
 
         [Fact]
         public void Exists()
         {
-            var type = typeof(LCIDConversionAttributeTests);
-            var method = type.GetTypeInfo().DeclaredMethods.Single(m => m.Name == "Func");
-            var attr = method.GetCustomAttributes(typeof(LCIDConversionAttribute), false).OfType<LCIDConversionAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
-            Assert.Equal(1337, attr.Value);
+            Type type = typeof(LCIDConversionAttributeTests);
+            MethodInfo method = type.GetTypeInfo().DeclaredMethods.Single(m => m.Name == "Func");
+            LCIDConversionAttribute attribute = Assert.Single(method.GetCustomAttributes<LCIDConversionAttribute>(false));
+            Assert.Equal(1337, attribute.Value);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(0)]
+        [InlineData(1)]
+        public void Ctor_Lcid(int lcid)
+        {
+            var attribute = new LCIDConversionAttribute(lcid);
+            Assert.Equal(lcid, attribute.Value);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/MarshalTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/MarshalTests.cs
index a7ccb59f8c..a4c97eb480 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/MarshalTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/MarshalTests.cs
@@ -3,7 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using Xunit;
-using System.Collections.Generic;
 using System.Security;
 
 namespace System.Runtime.InteropServices
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/PrimaryInteropAssemblyAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/PrimaryInteropAssemblyAttributeTests.cs
index 2135e9ccaa..68f85ff0c2 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/PrimaryInteropAssemblyAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/PrimaryInteropAssemblyAttributeTests.cs
@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Linq;
 using System.Reflection;
 using System.Runtime.InteropServices;
 using Xunit;
@@ -16,12 +15,22 @@ namespace System.Runtime.InteropServices.Tests
         [Fact]
         public void Exists()
         {
-            var type = typeof(PrimaryInteropAssemblyAttributeTests);
-            var assembly = type.GetTypeInfo().Assembly;
-            var attr = assembly.GetCustomAttributes(typeof(PrimaryInteropAssemblyAttribute), false).OfType<PrimaryInteropAssemblyAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
-            Assert.Equal(1, attr.MajorVersion);
-            Assert.Equal(2, attr.MinorVersion);
+            Type type = typeof(PrimaryInteropAssemblyAttributeTests);
+            Assembly assembly = type.GetTypeInfo().Assembly;
+            PrimaryInteropAssemblyAttribute attribute = Assert.Single(assembly.GetCustomAttributes<PrimaryInteropAssemblyAttribute>());
+            Assert.Equal(1, attribute.MajorVersion);
+            Assert.Equal(2, attribute.MinorVersion);
+        }
+
+        [Theory]
+        [InlineData(-1, -2)]
+        [InlineData(0, 0)]
+        [InlineData(1, 2)]
+        public void Ctor_MajorVersion_MinorVersion(int major, int minor)
+        {
+            var attribute = new PrimaryInteropAssemblyAttribute(major, minor);
+            Assert.Equal(major, attribute.MajorVersion);
+            Assert.Equal(minor, attribute.MinorVersion);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ProgIdAttributeTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ProgIdAttributeTests.cs
index a0e00935cd..402fb5569f 100644
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ProgIdAttributeTests.cs
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/ProgIdAttributeTests.cs
@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Linq;
-using System.Reflection;
 using Xunit;
 
 namespace System.Runtime.InteropServices.Tests
@@ -14,10 +12,18 @@ namespace System.Runtime.InteropServices.Tests
         [Fact]
         public void Exists()
         {
-            var type = typeof(ProgIdAttributeTests);
-            var attr = type.GetCustomAttributes(typeof(ProgIdAttribute), false).OfType<ProgIdAttribute>().SingleOrDefault();
-            Assert.NotNull(attr);
-            Assert.Equal("pizza", attr.Value);
+            Type type = typeof(ProgIdAttributeTests);
+            ProgIdAttribute attribute = Assert.IsType<ProgIdAttribute>(Assert.Single(type.GetCustomAttributes(typeof(ProgIdAttribute), false)));
+            Assert.Equal("pizza", attribute.Value);
+        }
+
+        [Theory]
+        [InlineData(null)]
+        [InlineData("ProgId")]
+        public void Ctor_ProgId(string progId)
+        {
+            var attribute = new ProgIdAttribute(progId);
+            Assert.Equal(progId, attribute.Value);
         }
     }
 }
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/RuntimeEnvironmentTest.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/RuntimeEnvironmentTest.cs
deleted file mode 100644
index b758813c4b..0000000000
--- a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/RuntimeEnvironmentTest.cs
+++ /dev/null
@@ -1,43 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System.Reflection;
-using System.Runtime;
-using System.Runtime.InteropServices;
-using System.IO;
-using Xunit;
-
-namespace System.Runtime.InteropServices
-{
-    public static class RuntimeEnvironmentTest
-    {
-        [Fact]
-        public static void RuntimeEnvironmentRuntimeDirectory()
-        {
-            Assert.True(Directory.Exists(RuntimeEnvironment.GetRuntimeDirectory()));
-        }
-
-        [Fact]
-        [ActiveIssue(20600, TargetFrameworkMonikers.UapAot)]
-        public static void RuntimeEnvironmentSysVersion()
-        {            
-            Assert.True(!String.IsNullOrEmpty(RuntimeEnvironment.GetSystemVersion()));
-        }
-
-        [Fact]
-        [SkipOnTargetFramework(TargetFrameworkMonikers.NetFramework)]
-        public static void RuntimeEnvironmentNegTest()
-        {
-            Type clsType = typeof(RuntimeEnvironmentTest);
-            Assembly assem = clsType.Assembly;
-            Assert.True(!RuntimeEnvironment.FromGlobalAccessCache(assem));
-
-            Assert.Throws<PlatformNotSupportedException>(() => RuntimeEnvironment.SystemConfigurationFile);
-
-            Guid guid;
-            Assert.Throws<PlatformNotSupportedException>(() => RuntimeEnvironment.GetRuntimeInterfaceAsObject(guid, guid));
-            Assert.Throws<PlatformNotSupportedException>(() => RuntimeEnvironment.GetRuntimeInterfaceAsIntPtr(guid, guid));
-        }
-    }
-}
diff --git a/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/RuntimeEnvironmentTests.cs b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/RuntimeEnvironmentTests.cs
new file mode 100644
index 0000000000..956399207d
--- /dev/null
+++ b/src/System.Runtime.InteropServices/tests/System/Runtime/InteropServices/RuntimeEnvironmentTests.cs
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using Xunit;
+
+namespace System.Runtime.InteropServices
+{
+    public class RuntimeEnvironmentTests
+    {
+        [Fact]
+        public void RuntimeEnvironmentRuntimeDirectory()
+        {
+            Assert.True(Directory.Exists(RuntimeEnvironment.GetRuntimeDirectory()));
+        }
+
+        [Fact]
+        [ActiveIssue(20600, TargetFrameworkMonikers.UapAot)]
+        public void RuntimeEnvironmentSysVersion()
+        {            
+            Assert.NotEmpty(RuntimeEnvironment.GetSystemVersion());
+        }
+
+        [Fact]
+        [SkipOnTargetFramework(TargetFrameworkMonikers.NetFramework, "SystemConfigurationFile is not supported on .NET Core.")]
+        public void SystemConfigurationFile_Get_ThrowsPlatformNotSupportedException()
+        {
+            Assert.Throws<PlatformNotSupportedException>(() => RuntimeEnvironment.SystemConfigurationFile);
+        }
+
+        [Fact]
+        [SkipOnTargetFramework(TargetFrameworkMonikers.NetFramework, "GetRuntimeInterfaceAsObject is not supported on .NET Core.")]
+        public void GetRuntimeInterfaceAsObject_Invoke_ThrowsPlatformNotSupportedException()
+        {
+            Assert.Throws<PlatformNotSupportedException>(() => RuntimeEnvironment.GetRuntimeInterfaceAsObject(Guid.Empty, Guid.Empty));
+        }
+
+        [Fact]
+        [SkipOnTargetFramework(TargetFrameworkMonikers.NetFramework, "GetRuntimeInterfaceAsIntPtr is not supported on .NET Core.")]
+        public void GetRuntimeInterfaceAsIntPtr_Invoke_ThrowsPlatformNotSupportedException()
+        {
+            Assert.Throws<PlatformNotSupportedException>(() => RuntimeEnvironment.GetRuntimeInterfaceAsIntPtr(Guid.Empty, Guid.Empty));
+        }
+
+        [Fact]
+        [SkipOnTargetFramework(TargetFrameworkMonikers.NetFramework, "FromGlobalAccessCache always returns true on .NET Core.")]
+        public void FromGlobalAccessCache_INvoke_ReturnsFalse()
+        {
+            Assert.False(RuntimeEnvironment.FromGlobalAccessCache(typeof(RuntimeEnvironmentTests).Assembly));
+            Assert.False(RuntimeEnvironment.FromGlobalAccessCache(null));
+        }
+    }
+}