diff --git a/src/test/java/io/github/artlibs/autotrace4j/At4jTest.java b/src/test/java/io/github/artlibs/autotrace4j/At4jTest.java
index c2b95cf..76043c4 100644
--- a/src/test/java/io/github/artlibs/autotrace4j/At4jTest.java
+++ b/src/test/java/io/github/artlibs/autotrace4j/At4jTest.java
@@ -322,8 +322,7 @@ void testHttpURLConnection() throws Exception {
     void testOkHttpClientAsync() throws Exception {
         // 01.Prepare
         OkHttpClient client = new OkHttpClient();
-        Request request = new Request.Builder()
-                .url(httpBinOrgUrl).build();
+        Request request = new Request.Builder().url(httpBinOrgUrl).build();
         final TupleResult[] asyncTupleHolder = new TupleResult[1];
         final Response[] responseHolder = new Response[1];
         CountDownLatch latch = new CountDownLatch(1);
@@ -332,8 +331,9 @@ void testOkHttpClientAsync() throws Exception {
         client.newCall(request).enqueue(new Callback() {
             @Override
             public void onFailure(@NotNull Call call, @NotNull IOException e) {
-                System.err.println(e.getMessage());
                 asyncTupleHolder[0] = generateResult();
+                System.err.println(asyncTupleHolder[0]);
+                System.err.println(e.getMessage());
                 latch.countDown();
             }
 
@@ -341,6 +341,8 @@ public void onFailure(@NotNull Call call, @NotNull IOException e) {
             public void onResponse(@NotNull Call call, @NotNull Response resp) {
                 asyncTupleHolder[0] = generateResult();
                 responseHolder[0] = resp;
+                System.err.println(asyncTupleHolder[0]);
+                System.err.println(resp);
                 latch.countDown();
             }
         });
diff --git a/src/test/java/io/github/artlibs/testsupport/TupleResult.java b/src/test/java/io/github/artlibs/testsupport/TupleResult.java
index 39117a7..11bad21 100644
--- a/src/test/java/io/github/artlibs/testsupport/TupleResult.java
+++ b/src/test/java/io/github/artlibs/testsupport/TupleResult.java
@@ -1,5 +1,7 @@
 package io.github.artlibs.testsupport;
 
+import com.alibaba.fastjson.JSON;
+
 /**
  * Tuple
  *
@@ -72,4 +74,9 @@ public Object getValue5() {
     public void setValue5(Object value5) {
         this.value5 = value5;
     }
+
+    @Override
+    public String toString() {
+        return JSON.toJSONString(this);
+    }
 }