diff --git a/loki-logback-appender/src/test/java/com/github/loki4j/logback/Generators.java b/loki-logback-appender/src/test/java/com/github/loki4j/logback/Generators.java
index e2655d0e..b815ad6f 100644
--- a/loki-logback-appender/src/test/java/com/github/loki4j/logback/Generators.java
+++ b/loki-logback-appender/src/test/java/com/github/loki4j/logback/Generators.java
@@ -1,16 +1,12 @@
 package com.github.loki4j.logback;
 
 import java.io.IOException;
-import java.nio.ByteBuffer;
-import java.nio.charset.StandardCharsets;
 import java.time.Instant;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.ThreadLocalRandom;
-import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.BiFunction;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -19,7 +15,6 @@
 import org.slf4j.Marker;
 
 import com.github.loki4j.client.batch.LogRecord;
-import com.github.loki4j.client.batch.LogRecordBatch;
 import com.github.loki4j.client.http.HttpConfig;
 import com.github.loki4j.client.http.Loki4jHttpClient;
 import com.github.loki4j.client.pipeline.PipelineConfig;
@@ -28,7 +23,7 @@
 import com.github.loki4j.testkit.dummy.DummyHttpClient;
 import com.github.loki4j.testkit.dummy.ExceptionGenerator;
 import com.github.loki4j.testkit.dummy.LokiHttpServerMock;
-import com.github.loki4j.testkit.dummy.StringPayload;
+import com.github.loki4j.testkit.dummy.StringWriter;
 import com.github.loki4j.testkit.dummy.DummyHttpClient.SendInvocation;
 
 import ch.qos.logback.classic.Level;
@@ -46,28 +41,6 @@ public class Generators {
 
     static HttpConfig.Builder defaultHttpConfig = HttpConfig.builder();
 
-    public static String batchToString(LogRecordBatch batch) {
-        var s = new StringBuilder();
-        for (int i = 0; i < batch.size(); i++) {
-            var r = batch.get(i);
-            s
-                .append(Arrays.toString(r.stream.labels))
-                .append(StringPayload.LABELS_MESSAGE_SEPARATOR)
-                .append(Arrays.toString(r.metadata))
-                .append(StringPayload.LABELS_MESSAGE_SEPARATOR)
-                .append("ts=")
-                .append(r.timestampMs)
-                .append(" ")
-                .append(r.message)
-                .append('\n');
-        }
-        return s.toString();
-    }
-
-    public static String batchToString(LogRecord[] records) {
-        return batchToString(new LogRecordBatch(records));
-    }
-
     public static LokiHttpServerMock lokiMock(int port) {
         try {
 			return new LokiHttpServerMock(port);
@@ -377,63 +350,6 @@ public static InfiniteEventIterator from(LoggingEvent[] sampleEvents) {
         }
     }
 
-    public static class StringWriter implements Writer {
-        private final ByteBufferFactory bf;
-        private ByteBuffer b;
-        private int size = 0;
-        public StringWriter(int capacity, ByteBufferFactory bufferFactory) {
-            bf = bufferFactory;
-            b = bf.allocate(capacity);
-        }
-        @Override
-        public void serializeBatch(LogRecordBatch batch) {
-            b.clear();
-            var str = batchToString(batch);
-            var data = str.getBytes(StandardCharsets.UTF_8);
-            if (b.capacity() < data.length) b = bf.allocate(data.length);
-            b.put(data);
-            b.flip();
-            size = data.length;
-        }
-        @Override
-        public int size() {
-            return size;
-        }
-        @Override
-        public void toByteBuffer(ByteBuffer buffer) {
-            buffer.put(b);
-            buffer.flip();
-        }
-        @Override
-        public byte[] toByteArray() {
-            byte[] r = new byte[b.remaining()];
-            b.get(r);
-            return r;
-        }
-        @Override
-        public void reset() {
-            size = 0;
-            b.clear();
-        }
-        @Override
-        public boolean isBinary() {
-            return false;
-        }
-    }
-
-    public static class FailingStringWriter extends StringWriter {
-        public AtomicBoolean fail = new AtomicBoolean(false);
-        public FailingStringWriter(int capacity, ByteBufferFactory bufferFactory) {
-            super(capacity, bufferFactory);
-        }
-        @Override
-        public void serializeBatch(LogRecordBatch batch) {
-            if (fail.get())
-                throw new RuntimeException("Text exception");
-            super.serializeBatch(batch);
-        }
-    }
-
     public static class DummyHttpSender extends WrappingHttpSender<DummyHttpClient> {
 
         public DummyHttpSender() {
diff --git a/loki-logback-appender/src/test/java/com/github/loki4j/logback/Loki4jAppenderTest.java b/loki-logback-appender/src/test/java/com/github/loki4j/logback/Loki4jAppenderTest.java
index b71a3dcc..95c55071 100644
--- a/loki-logback-appender/src/test/java/com/github/loki4j/logback/Loki4jAppenderTest.java
+++ b/loki-logback-appender/src/test/java/com/github/loki4j/logback/Loki4jAppenderTest.java
@@ -10,9 +10,9 @@
 
 import org.junit.Test;
 
-import com.github.loki4j.logback.Generators.FailingStringWriter;
 import com.github.loki4j.logback.Generators.WrappingHttpSender;
 import com.github.loki4j.testkit.dummy.FailingHttpClient;
+import com.github.loki4j.testkit.dummy.FailingStringWriter;
 import com.github.loki4j.testkit.dummy.StringPayload;
 import com.github.loki4j.testkit.dummy.SuspendableHttpClient;
 import com.github.loki4j.testkit.dummy.FailingHttpClient.FailureType;
diff --git a/testkit/src/main/java/com/github/loki4j/testkit/dummy/FailingStringWriter.java b/testkit/src/main/java/com/github/loki4j/testkit/dummy/FailingStringWriter.java
new file mode 100644
index 00000000..d5e36496
--- /dev/null
+++ b/testkit/src/main/java/com/github/loki4j/testkit/dummy/FailingStringWriter.java
@@ -0,0 +1,21 @@
+package com.github.loki4j.testkit.dummy;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import com.github.loki4j.client.batch.LogRecordBatch;
+import com.github.loki4j.client.util.ByteBufferFactory;
+
+public class FailingStringWriter extends StringWriter {
+    public AtomicBoolean fail = new AtomicBoolean(false);
+
+    public FailingStringWriter(int capacity, ByteBufferFactory bufferFactory) {
+        super(capacity, bufferFactory);
+    }
+
+    @Override
+    public void serializeBatch(LogRecordBatch batch) {
+        if (fail.get())
+            throw new RuntimeException("Text exception");
+        super.serializeBatch(batch);
+    }
+}
\ No newline at end of file
diff --git a/testkit/src/main/java/com/github/loki4j/testkit/dummy/StringWriter.java b/testkit/src/main/java/com/github/loki4j/testkit/dummy/StringWriter.java
new file mode 100644
index 00000000..5c41ae1b
--- /dev/null
+++ b/testkit/src/main/java/com/github/loki4j/testkit/dummy/StringWriter.java
@@ -0,0 +1,80 @@
+package com.github.loki4j.testkit.dummy;
+
+import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
+
+import java.util.Arrays;
+
+import com.github.loki4j.client.batch.LogRecordBatch;
+import com.github.loki4j.client.util.ByteBufferFactory;
+import com.github.loki4j.client.writer.Writer;
+
+public class StringWriter implements Writer {
+    private final ByteBufferFactory bf;
+    private ByteBuffer b;
+    private int size = 0;
+
+    public StringWriter(int capacity, ByteBufferFactory bufferFactory) {
+        bf = bufferFactory;
+        b = bf.allocate(capacity);
+    }
+
+    public static String batchToString(LogRecordBatch batch) {
+        var s = new StringBuilder();
+        for (int i = 0; i < batch.size(); i++) {
+            var r = batch.get(i);
+            s
+                .append(Arrays.toString(r.stream.labels))
+                .append(StringPayload.LABELS_MESSAGE_SEPARATOR)
+                .append(Arrays.toString(r.metadata))
+                .append(StringPayload.LABELS_MESSAGE_SEPARATOR)
+                .append("ts=")
+                .append(r.timestampMs)
+                .append(" ")
+                .append(r.message)
+                .append('\n');
+        }
+        return s.toString();
+    }
+
+    @Override
+    public void serializeBatch(LogRecordBatch batch) {
+        b.clear();
+        var str = batchToString(batch);
+        var data = str.getBytes(StandardCharsets.UTF_8);
+        if (b.capacity() < data.length)
+            b = bf.allocate(data.length);
+        b.put(data);
+        b.flip();
+        size = data.length;
+    }
+
+    @Override
+    public int size() {
+        return size;
+    }
+
+    @Override
+    public void toByteBuffer(ByteBuffer buffer) {
+        buffer.put(b);
+        buffer.flip();
+    }
+
+    @Override
+    public byte[] toByteArray() {
+        byte[] r = new byte[b.remaining()];
+        b.get(r);
+        return r;
+    }
+
+    @Override
+    public void reset() {
+        size = 0;
+        b.clear();
+    }
+
+    @Override
+    public boolean isBinary() {
+        return false;
+    }
+}
\ No newline at end of file