added empty error

Raliway.Tests/Errors/Serialization_RoundTrip.cs

@@ -152,19 +152,31 @@ public class Serialization_RoundTrip
         }
 
         [Fact]
-        public void Empty_ManyErrors_round_trip()
+        public void EmptyError_serializes_to_null()
         {
             // Given
-            Error original = Error.Many(Array.Empty<Error>());
+            var error = Error.Empty;
 
             // When
-            var json = JsonSerializer.Serialize(original);
-            var deserialized = JsonSerializer.Deserialize<Error>(json);
+            var json = JsonSerializer.Serialize(error);
 
             // Then
-            deserialized.ShouldBeOfType<ManyErrors>();
-            deserialized!.IsEmpty.ShouldBeTrue();
-            deserialized.Count.ShouldBe(0);
+            json.ShouldBe("null");
+        }
+
+        [Fact]
+        public void EmptyError_filtered_from_ManyErrors_serialization()
+        {
+            // Given
+            var real = Error.New("real_error");
+            var errors = Error.Many(Error.Empty, real);
+
+            // When
+            var json = JsonSerializer.Serialize(errors);
+
+            // Then
+            json.ShouldNotContain("empty");
+            json.ShouldContain("real_error");
         }
 
         [Fact]