diff --git a/http-generator-core/src/test/java/io/avaje/http/generator/core/JsonBUtilTest.java b/http-generator-core/src/test/java/io/avaje/http/generator/core/JsonBUtilTest.java
new file mode 100644
index 00000000..838e2031
--- /dev/null
+++ b/http-generator-core/src/test/java/io/avaje/http/generator/core/JsonBUtilTest.java
@@ -0,0 +1,46 @@
+package io.avaje.http.generator.core;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.StringWriter;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class JsonBUtilTest {
+
+  @Test
+  void writeType() {
+    UType uType = UType.parse("my.pack.Foo");
+    var sw = new StringWriter();
+    JsonBUtil.writeType(uType, new Append(sw));
+
+    assertThat(sw.toString()).isEqualTo("Foo.class)");
+  }
+
+  @Test
+  void writeType_generic() {
+    UType uType = UType.parse("my.pack.Some<java.lang.String>");
+    var sw = new StringWriter();
+    JsonBUtil.writeType(uType, new Append(sw));
+
+    assertThat(sw.toString()).isEqualTo("Types.newParameterizedType(Some.class, String.class))");
+  }
+
+  @Test
+  void writeType_genericWithWildcard() {
+    UType uType = UType.parse("my.pack.Some<java.lang.String, ?>");
+    var sw = new StringWriter();
+    JsonBUtil.writeType(uType, new Append(sw));
+
+    assertThat(sw.toString()).isEqualTo("Types.newParameterizedType(Some.class, String.class, Object.class))");
+  }
+
+  @Test
+  void writeType_genericWithMultiple() {
+    UType uType = UType.parse("my.pack.Some<java.lang.String, my.other.Foo>");
+    var sw = new StringWriter();
+    JsonBUtil.writeType(uType, new Append(sw));
+
+    assertThat(sw.toString()).isEqualTo("Types.newParameterizedType(Some.class, String.class, Foo.class))");
+  }
+}