diff --git a/dd-trace/dd-trace.gradle b/dd-trace/dd-trace.gradle
index e2bce02818..690fa7223b 100644
--- a/dd-trace/dd-trace.gradle
+++ b/dd-trace/dd-trace.gradle
@@ -17,8 +17,6 @@ whitelistedInstructionClasses += whitelistedBranchClasses += [
   'com.datadoghq.trace.DDTags',
   'com.datadoghq.trace.DDTraceInfo',
   'com.datadoghq.trace.util.Clock',
-  //TODO: Refactor the class in order to make it more testable
-  'com.datadoghq.trace.writer.DDAgentWriter',
 
 ]
 
@@ -42,6 +40,8 @@ dependencies {
   testCompile group: 'org.spockframework', name: 'spock-core', version: '1.0-groovy-2.4'
   testCompile group: 'org.codehaus.groovy', name: 'groovy-all', version: '2.4.4'
   testCompile group: 'io.ratpack', name: 'ratpack-groovy-test', version: '1.4.6'
+  testCompile group: 'org.objenesis', name: 'objenesis', version: '2.6'
+  testCompile group: 'cglib', name: 'cglib-nodep', version: '3.2.5'
 
   jmh 'commons-io:commons-io:2.4'
 }
diff --git a/dd-trace/src/main/java/com/datadoghq/trace/writer/DDAgentWriter.java b/dd-trace/src/main/java/com/datadoghq/trace/writer/DDAgentWriter.java
index 80f0576378..3b27f6576c 100644
--- a/dd-trace/src/main/java/com/datadoghq/trace/writer/DDAgentWriter.java
+++ b/dd-trace/src/main/java/com/datadoghq/trace/writer/DDAgentWriter.java
@@ -30,13 +30,13 @@ public class DDAgentWriter implements Writer {
   public static final int DEFAULT_PORT = 8126;
 
   /** Maximum number of traces kept in memory */
-  private static final int DEFAULT_MAX_TRACES = 1000;
+  static final int DEFAULT_MAX_TRACES = 1000;
 
   /** Timeout for the API in seconds */
-  private static final long API_TIMEOUT_SECONDS = 1;
+  static final long API_TIMEOUT_SECONDS = 1;
 
   /** Flush interval for the API in seconds */
-  private static final long FLUSH_TIME_SECONDS = 1;
+  static final long FLUSH_TIME_SECONDS = 1;
 
   /** Scheduled thread pool, acting like a cron */
   private final ScheduledExecutorService scheduledExecutor = Executors.newScheduledThreadPool(1);
@@ -57,9 +57,13 @@ public class DDAgentWriter implements Writer {
   }
 
   public DDAgentWriter(final DDApi api) {
+    this(api, new WriterQueue<List<DDBaseSpan<?>>>(DEFAULT_MAX_TRACES));
+  }
+
+  public DDAgentWriter(final DDApi api, final WriterQueue<List<DDBaseSpan<?>>> queue) {
     super();
     this.api = api;
-    traces = new WriterQueue<>(DEFAULT_MAX_TRACES);
+    traces = queue;
   }
 
   /* (non-Javadoc)
@@ -67,7 +71,6 @@ public class DDAgentWriter implements Writer {
    */
   @Override
   public void write(final List<DDBaseSpan<?>> trace) {
-
     final List<DDBaseSpan<?>> removed = traces.add(trace);
     if (removed != null && !queueFullReported) {
       log.debug("Queue is full, traces will be discarded, queue size: {}", DEFAULT_MAX_TRACES);
diff --git a/dd-trace/src/test/groovy/com/datadoghq/trace/writer/DDAgentWriterTest.groovy b/dd-trace/src/test/groovy/com/datadoghq/trace/writer/DDAgentWriterTest.groovy
new file mode 100644
index 0000000000..a4917b46b3
--- /dev/null
+++ b/dd-trace/src/test/groovy/com/datadoghq/trace/writer/DDAgentWriterTest.groovy
@@ -0,0 +1,93 @@
+package com.datadoghq.trace.writer
+
+import com.datadoghq.trace.DDBaseSpan
+import spock.lang.Specification
+
+import static com.datadoghq.trace.SpanFactory.newSpanOf
+import static org.mockito.Mockito.mock
+import static org.mockito.Mockito.verifyNoMoreInteractions
+
+class DDAgentWriterTest extends Specification {
+
+
+  def "calls to the API are scheduled"() {
+
+    setup:
+    def api = Mock(DDApi)
+    def writer = new DDAgentWriter(api)
+
+    when:
+    writer.start()
+    Thread.sleep(flush_time_wait)
+
+    then:
+    0 * api.sendTraces(_ as List)
+
+    when:
+    for (def i = 0; i < tick; i++) {
+      writer.write(trace)
+      Thread.sleep(flush_time_wait)
+    }
+
+    then:
+    tick * api.sendTraces([trace])
+
+    where:
+    trace = [newSpanOf(0)]
+    flush_time_wait = (int) (1.2 * (DDAgentWriter.FLUSH_TIME_SECONDS * 1_000))
+    tick << [1, 3]
+
+
+  }
+
+  def "check if trace has been added by force"() {
+
+    setup:
+    def traces = new WriterQueue<List<DDBaseSpan<?>>>(capacity)
+    def writer = new DDAgentWriter(Mock(DDApi), traces)
+
+    when:
+    for (def i = 0; i < capacity; i++) {
+      writer.write([])
+    }
+
+    then:
+    traces.size() == capacity
+
+    when:
+    writer.write(trace)
+
+    then:
+    traces.size() == capacity
+    traces.getAll().contains(trace)
+
+    where:
+    trace = [newSpanOf(0)]
+    capacity = 10
+
+
+  }
+
+  def "check that are no interactions after close"() {
+
+    setup:
+    def api = mock(DDApi)
+    def writer = new DDAgentWriter(api)
+    writer.start()
+
+    when:
+    writer.close()
+    writer.write([])
+    Thread.sleep(flush_time_wait)
+
+    then:
+    verifyNoMoreInteractions(api)
+
+    where:
+    flush_time_wait = (int) (1.2 * (DDAgentWriter.FLUSH_TIME_SECONDS * 1_000))
+
+
+  }
+
+
+}