diff --git a/src/Ramstack.HtmxToolkit/Internal/EnumHelper.cs b/src/Ramstack.HtmxToolkit/Internal/EnumHelper.cs
index 8a13b89..9f60888 100644
--- a/src/Ramstack.HtmxToolkit/Internal/EnumHelper.cs
+++ b/src/Ramstack.HtmxToolkit/Internal/EnumHelper.cs
@@ -1,3 +1,5 @@
+using System.Diagnostics;
+
 using Ramstack.HtmxToolkit.Configuration;
 
 namespace Ramstack.HtmxToolkit.Internal;
@@ -15,8 +17,12 @@ internal static class EnumHelper
     /// <returns>
     /// <c>blob</c> or <c>arraybuffer</c>.
     /// </returns>
-    public static string GetWsBinaryTypeValue(this HtmxBinaryType value) =>
-        value == HtmxBinaryType.Blob ? "blob" : "arraybuffer";
+    public static string GetWsBinaryTypeValue(this HtmxBinaryType value)
+    {
+        Debug.Assert(value is HtmxBinaryType.Blob or HtmxBinaryType.ArrayBuffer);
+
+        return value == HtmxBinaryType.Blob ? "blob" : "arraybuffer";
+    }
 
     /// <summary>
     /// Converts a <see cref="HtmxScrollBehavior" /> value
@@ -28,6 +34,11 @@ public static string GetWsBinaryTypeValue(this HtmxBinaryType value) =>
     /// </returns>
     public static string GetScrollBehaviorValue(this HtmxScrollBehavior value)
     {
+        Debug.Assert(value
+            is HtmxScrollBehavior.Auto
+            or HtmxScrollBehavior.Smooth
+            or HtmxScrollBehavior.Instant);
+
         return value switch
         {
             HtmxScrollBehavior.Auto => "auto",
@@ -59,6 +70,20 @@ public static string GetScrollBehaviorValue(this HtmxScrollBehavior value)
     /// </returns>
     public static string GetSwapValue(this HtmxSwap value)
     {
+        Debug.Assert(value
+            is HtmxSwap.InnerHtml
+            or HtmxSwap.OuterHtml
+            or HtmxSwap.InnerMorph
+            or HtmxSwap.OuterMorph
+            or HtmxSwap.OuterSync
+            or HtmxSwap.TextContent
+            or HtmxSwap.BeforeBegin
+            or HtmxSwap.AfterBegin
+            or HtmxSwap.BeforeEnd
+            or HtmxSwap.AfterEnd
+            or HtmxSwap.Delete
+            or HtmxSwap.None);
+
         return value switch
         {
             HtmxSwap.InnerHtml => "innerHTML",
@@ -85,6 +110,17 @@ public static string GetSwapValue(this HtmxSwap value)
     /// </returns>
     public static string GetHttpVerbValue(this HttpVerb value)
     {
+        Debug.Assert(value
+            is HttpVerb.Get
+            or HttpVerb.Head
+            or HttpVerb.Post
+            or HttpVerb.Put
+            or HttpVerb.Delete
+            or HttpVerb.Connect
+            or HttpVerb.Options
+            or HttpVerb.Trace
+            or HttpVerb.Patch);
+
         return value switch
         {
             HttpVerb.Get => "get",
@@ -109,6 +145,11 @@ public static string GetHttpVerbValue(this HttpVerb value)
     /// </returns>
     public static string GetFetchModeValue(this HtmxFetchMode value)
     {
+        Debug.Assert(value
+            is HtmxFetchMode.SameOrigin
+            or HtmxFetchMode.Cors
+            or HtmxFetchMode.NoCors);
+
         return value switch
         {
             HtmxFetchMode.SameOrigin => "same-origin",
diff --git a/src/Ramstack.HtmxToolkit/Serialization/HtmxHistoryModeJsonConverter.cs b/src/Ramstack.HtmxToolkit/Serialization/HtmxHistoryModeJsonConverter.cs
index 7321292..85463ae 100644
--- a/src/Ramstack.HtmxToolkit/Serialization/HtmxHistoryModeJsonConverter.cs
+++ b/src/Ramstack.HtmxToolkit/Serialization/HtmxHistoryModeJsonConverter.cs
@@ -1,3 +1,4 @@
+using System.Diagnostics;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 
@@ -23,6 +24,11 @@ internal sealed class HtmxHistoryModeJsonConverter : JsonConverter<HtmxHistoryMo
     /// <inheritdoc />
     public override void Write(Utf8JsonWriter writer, HtmxHistoryMode? value, JsonSerializerOptions options)
     {
+        Debug.Assert(value is null
+            or HtmxHistoryMode.Enabled
+            or HtmxHistoryMode.Disabled
+            or HtmxHistoryMode.Reload);
+
         // NOTE: value is never null here: null-valued properties are omitted
         // by JsonIgnoreCondition.WhenWritingNull before this converter is invoked.
         switch (value.GetValueOrDefault())
diff --git a/tests/Ramstack.HtmxToolkit.Tests/EnumHelperTests.cs b/tests/Ramstack.HtmxToolkit.Tests/EnumHelperTests.cs
index 486dcc5..c54f231 100644
--- a/tests/Ramstack.HtmxToolkit.Tests/EnumHelperTests.cs
+++ b/tests/Ramstack.HtmxToolkit.Tests/EnumHelperTests.cs
@@ -86,24 +86,4 @@ public void GetScrollBehaviorValue_ReturnsExpectedString(HtmxScrollBehavior valu
     [TestCase(HtmxFetchMode.NoCors, "no-cors")]
     public void GetFetchModeValue_ReturnsExpectedString(HtmxFetchMode value, string expected) =>
         Assert.That(value.GetFetchModeValue(), Is.EqualTo(expected));
-
-    [Test]
-    public void GetSwapValue_ReturnsNone_ForUndefinedValue() =>
-        Assert.That(((HtmxSwap)999).GetSwapValue(), Is.EqualTo("none"));
-
-    [Test]
-    public void GetHttpVerbValue_ReturnsPatch_ForUndefinedValue() =>
-        Assert.That(((HttpVerb)999).GetHttpVerbValue(), Is.EqualTo("patch"));
-
-    [Test]
-    public void GetScrollBehaviorValue_ReturnsInstant_ForUndefinedValue() =>
-        Assert.That(((HtmxScrollBehavior)999).GetScrollBehaviorValue(), Is.EqualTo("instant"));
-
-    [Test]
-    public void GetWsBinaryTypeValue_ReturnsArrayBuffer_ForUndefinedValue() =>
-        Assert.That(((HtmxBinaryType)999).GetWsBinaryTypeValue(), Is.EqualTo("arraybuffer"));
-
-    [Test]
-    public void GetFetchModeValue_ReturnsNoCors_ForUndefinedValue() =>
-        Assert.That(((HtmxFetchMode)999).GetFetchModeValue(), Is.EqualTo("no-cors"));
 }