Add BeJsonResult and WithValue assertions.

Author: faddiv

src/FluentAssertions.AspNetCore.Mvc/ActionResultAssertions.cs

@@ -86,6 +86,21 @@ public EmptyResult BeEmptyResult(string reason, params object[] reasonArgs)
             return Subject as EmptyResult;
         }
 
+        public JsonResultAssertions BeJsonResult()
+        {
+            return BeJsonResult(string.Empty, null);
+        }
+
+        public JsonResultAssertions BeJsonResult(string reason, params object[] reasonArgs)
+        {
+            Execute.Assertion
+                .BecauseOf(reason, reasonArgs)
+                .ForCondition(Subject is JsonResult)
+                .FailWith(Constants.CommonFailMessage, typeof(JsonResult).Name, Subject.GetType().Name);
+
+            return new JsonResultAssertions(Subject as JsonResult);
+        }
+
         /// <summary>
         /// Asserts that the subject is a <see cref="RedirectToRouteResult"/>.
         /// </summary>

src/FluentAssertions.AspNetCore.Mvc/JsonResultAssertions.cs

@@ -0,0 +1,45 @@
+using FluentAssertions.Execution;
+using FluentAssertions.Primitives;
+using Microsoft.AspNetCore.Mvc;
+using System;
+
+namespace FluentAssertions.AspNetCore.Mvc
+{
+    public class JsonResultAssertions : ObjectAssertions
+    {
+        #region Public Constructors
+
+        public JsonResultAssertions(JsonResult subject) : base(subject)
+        {
+
+        }
+
+        #endregion
+
+        #region Public Properties
+
+        #endregion
+
+        #region Private Properties
+
+        private JsonResult JsonResultSubject => (JsonResult)Subject;
+
+        #endregion Private Properties
+
+        #region Public Methods
+
+        public JsonResultAssertions WithValue(object expectedValue, string reason = "",
+            params object[] reasonArgs)
+        {
+            var actualValue = JsonResultSubject.Value;
+
+            Execute.Assertion
+                .ForCondition(Equals(expectedValue, actualValue))
+                .BecauseOf(reason, reasonArgs)
+                .FailWith(FailureMessages.CommonFailMessage, "JsonResult.Value", expectedValue, actualValue);
+            return this;
+        }
+
+        #endregion
+    }
+}

tests/FluentAssertions.AspNetCore.Mvc.Tests/ActionResultAssertions_Tests.cs

@@ -42,6 +42,23 @@ public void BeEmpty_GivenNotEmpty_ShouldPass()
                 .WithMessage("Expected ActionResult to be \"EmptyResult\", but found \"ViewResult\"");
         }
 
+        [Fact]
+        public void BeJson_GivenJson_ShouldPass()
+        {
+            ActionResult result = new JsonResult(new object());
+            result.Should()
+                .BeJsonResult();
+        }
+
+        [Fact]
+        public void BeJson_GivenNotJson_ShouldFail()
+        {
+            ActionResult result = new ViewResult();
+            Action a = () => result.Should().BeJsonResult();
+            a.Should().Throw<Exception>()
+                .WithMessage("Expected ActionResult to be \"JsonResult\", but found \"ViewResult\"");
+        }
+
         [Fact]
         public void BeRedirectToRoute_GivenRedirectToRoute_ShouldPass()
         {

tests/FluentAssertions.AspNetCore.Mvc.Tests/JsonResultAssertions_Tests.cs

@@ -0,0 +1,31 @@
+using FluentAssertions.Mvc.Tests.Helpers;
+using Microsoft.AspNetCore.Mvc;
+using System;
+using Xunit;
+
+namespace FluentAssertions.AspNetCore.Mvc.Tests
+{
+    public class JsonResultAssertions_Tests
+    {
+        [Fact]
+        public void WithValue_GivenValue_ShouldPass()
+        {
+            ActionResult result = new JsonResult("value");
+            result.Should().BeJsonResult().WithValue("value");
+        }
+
+        [Fact]
+        public void WithValue_GivenUnexpected_ShouldFail()
+        {
+            var actualValue = "xyz";
+            var expectedValue = "value";
+            ActionResult result = new JsonResult(actualValue);
+            var failureMessage = FailureMessageHelper.Format(FailureMessages.CommonFailMessage, "JsonResult.Value", expectedValue, actualValue);
+
+            Action a = () => result.Should().BeJsonResult().WithValue(expectedValue);
+
+            a.Should().Throw<Exception>()
+                .WithMessage(failureMessage);
+        }
+    }
+}