Implemented: HaveValueKind.

Src/FluentAssertions/Json/JsonElementAssertions.cs

@@ -1,20 +1,47 @@
-using System.Text.Json;
+using System.Diagnostics;
+using System.Text.Json;
 using FluentAssertions.Execution;
 
 namespace FluentAssertions.Json;
 
 /// <summary>
 /// Contains a number of methods to assert that an <see cref="JsonElement" /> is in the expected state.
 /// </summary>
+[DebuggerNonUserCode]
 public class JsonElementAssertions
 {
     public JsonElement Subject { get; }
 
+    /// <summary>
+    ///     Initializes a new instance of the <see cref="JsonElementAssertions" /> class.
+    /// </summary>
+    /// <param name="subject">The subject.</param>
     public JsonElementAssertions(JsonElement subject)
     {
         Subject = subject;
     }
 
+    /// <summary>
+    ///     Asserts that the current <see cref="JsonElement"/> has the specified <see cref="JsonValueKind"/>.
+    /// </summary>
+    /// <param name="valueKind">The JSON string.</param>
+    /// <param name="because">
+    ///     A formatted phrase as is supported by <see cref="string.Format(string,object[])" /> explaining why the assertion
+    ///     is needed. If the phrase does not start with the word <i>because</i>, it is prepended automatically.
+    /// </param>
+    /// <param name="becauseArgs">
+    ///     Zero or more objects to format using the placeholders in <see paramref="because" />.
+    /// </param>
+    public AndConstraint<JsonElementAssertions> HaveValueKind(JsonValueKind valueKind, string because = "", params object[] becauseArgs)
+    {
+        Execute.Assertion
+            .BecauseOf(because, becauseArgs)
+            .ForCondition(Subject.ValueKind == valueKind)
+            .FailWith("Expected {context:JSON} to have value kind {0}{reason}, but found {1}.", valueKind, Subject.ValueKind);
+
+        return new(this);
+    }
+
     public void Be(long jsonNumber)
     {
         Execute.Assertion

Src/FluentAssertions/Json/JsonSerializerOptionsAssertions.cs

@@ -10,13 +10,13 @@ namespace FluentAssertions.Json;
 /// <summary>
 ///     Contains a number of methods to assert that an <see cref="JsonSerializerOptions" /> is in the expected state.
 /// </summary>
-// [DebuggerNonUserCode]
+[DebuggerNonUserCode]
 public class JsonSerializerOptionsAssertions : ReferenceTypeAssertions<JsonSerializerOptions, JsonSerializerOptionsAssertions>
 {
     /// <summary>
     ///     Initializes a new instance of the <see cref="JsonSerializerOptionsAssertions" /> class.
     /// </summary>
-    /// <param name="subject">The subject</param>
+    /// <param name="subject">The subject.</param>
     public JsonSerializerOptionsAssertions(JsonSerializerOptions subject)
         : base(subject)
     {

Tests/FluentAssertions.Specs/Json/JsonElementAssertionsSpecs.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Text.Json;
+using Xunit;
+using Xunit.Sdk;
+
+namespace FluentAssertions.Specs.Json;
+
+public class JsonElementAssertionsSpecs
+{
+    public class HaveValueKind
+    {
+        [Fact]
+        public void Throws_for_unexcepected_value_kind()
+        {
+            // Arrange
+            JsonSerializerOptions options = new();
+
+            // Act
+            Action act = () => options.Should().Serialize(42)
+                .And.Value.Should().HaveValueKind(JsonValueKind.String, because: "Why not?");
+
+            // Assert
+            act.Should().Throw<XunitException>()
+                .WithMessage("Expected options to have value kind JsonValueKind.String {value: 3} because Why not?, but found JsonValueKind.Number {value: 4}");
+        }
+
+        [Fact]
+        public void Guards_excepected_value_kinds()
+        {
+            // Arrange
+            JsonSerializerOptions options = new();
+
+            // Act + assert
+            options.Should().Serialize(42).And.Value.Should().HaveValueKind(JsonValueKind.Number);
+        }
+    }
+}