1 files changed, 52 insertions, 0 deletions
diff --git a/server/src/test/java/com/vaadin/server/CustomJSONSerializerTest.java b/server/src/test/java/com/vaadin/server/CustomJSONSerializerTest.java
new file mode 100644
index 0000000000..0c8b69fe62
--- /dev/null
+++ b/server/src/test/java/com/vaadin/server/CustomJSONSerializerTest.java
@@ -0,0 +1,52 @@
+package com.vaadin.server;
+
+import static org.junit.Assert.assertTrue;
+
+import java.lang.reflect.Type;
+
+import org.junit.Test;
+
+import com.vaadin.server.communication.JSONSerializer;
+import com.vaadin.ui.ConnectorTracker;
+
+import elemental.json.JsonValue;
+
+public class CustomJSONSerializerTest {
+    
+    public static class Foo {
+
+    }
+
+    public static class FooSerializer implements JSONSerializer<Foo> {
+
+        @Override
+        public Foo deserialize(Type type, JsonValue jsonValue,
+                ConnectorTracker connectorTracker) {
+            return null;
+        }
+
+        @Override
+        public JsonValue serialize(Foo value,
+                ConnectorTracker connectorTracker) {
+            return null;
+        }
+
+    }
+
+    @Test
+    public void testMultipleRegistration() {
+        boolean thrown = false;
+        try {
+            JsonCodec.setCustomSerializer(Foo.class, new FooSerializer());
+            JsonCodec.setCustomSerializer(Foo.class, new FooSerializer());
+        } catch (IllegalStateException ise) {
+            thrown = true;
+        } finally {
+            JsonCodec.setCustomSerializer(Foo.class, null);
+        }
+        assertTrue("Multiple serializer registrations for one class "
+                + "should throw an IllegalStateException", thrown);
+
+    }
+
+}