Add a couple of tests for fromdictionary

Author: javiercn

src/Components/src/Microsoft.AspNetCore.Components/ParameterCollection.cs

@@ -199,10 +199,10 @@ internal void CaptureSnapshot(ArrayBuilder<RenderTreeFrame> builder)
         }
 
         /// <summary>
-        /// 
+        /// Creates a new <see cref="ParameterCollection"/> from the given <see cref="IDictionary{TKey, TValue}"/>.
         /// </summary>
-        /// <param name="parameters"></param>
-        /// <returns></returns>
+        /// <param name="parameters">The <see cref="IDictionary{TKey, TValue}"/> with the parameters.</param>
+        /// <returns>A <see cref="ParameterCollection"/>.</returns>
         public static ParameterCollection FromDictionary(Dictionary<string, object> parameters)
         {
             var frames = new RenderTreeFrame[parameters.Count + 1];

src/Components/test/Microsoft.AspNetCore.Components.Test/ParameterCollectionTest.cs

@@ -1,12 +1,11 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using Microsoft.AspNetCore.Components;
-using Microsoft.AspNetCore.Components.Rendering;
-using Microsoft.AspNetCore.Components.RenderTree;
 using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Components.Rendering;
+using Microsoft.AspNetCore.Components.RenderTree;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Components.Test
@@ -240,6 +239,37 @@ public void ThrowsIfTryGetExistingValueWithIncorrectType()
             });
         }
 
+        [Fact]
+        public void FromDictionary_CanBeInitializedWithEmptyDictionary()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, object>();
+
+            // Act
+            var collection = ParameterCollection.FromDictionary(dictionary);
+
+            // Assert
+            Assert.Empty(collection.ToDictionary());
+        }
+
+        [Fact]
+        public void FromDictionary_RoundTrips()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, object>
+            {
+                ["IntValue"] = 1,
+                ["StringValue"] = "String"
+            };
+
+            // Act
+            var collection = ParameterCollection.FromDictionary(dictionary);
+
+            // Assert
+            Assert.Equal(dictionary, collection.ToDictionary());
+        }
+
+
         [Fact]
         public void CanConvertToReadOnlyDictionary()
         {