diff --git a/Test/Unit/Helper/DataTest.php b/Test/Unit/Helper/DataTest.php
new file mode 100644
index 0000000..9dfb888
--- /dev/null
+++ b/Test/Unit/Helper/DataTest.php
@@ -0,0 +1,208 @@
+<?php declare(strict_types=1);
+/** Copyright © Discorgento. All rights reserved. */
+
+namespace Discorgento\Queue\Test\Unit\Helper;
+
+use Discorgento\Queue\Api\Data\MessageInterface;
+use Discorgento\Queue\Api\MessageRepositoryInterface;
+use Discorgento\Queue\Helper\Data;
+use Discorgento\Queue\Model\MessageFactory;
+use Discorgento\Queue\Model\MessageRepository;
+use Discorgento\Queue\Model\ResourceModel\Message\Collection;
+use Discorgento\Queue\Model\ResourceModel\Message\CollectionFactory as MessageCollectionFactory;
+use Discorgento\Queue\Test\Job;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+
+class DataTest extends TestCase
+{
+    /**
+     * @var Data
+     */
+    private $instance;
+
+    /**
+     * @var MessageCollectionFactory|MockObject
+     */
+    private $messageCollectionFactoryMock;
+
+    /**
+     * @var MessageFactory|MockObject
+     */
+    private $messageFactoryMock;
+
+    /**
+     * @var MessageRepositoryInterface|MockObject
+     */
+    private $messageRepositoryMock;
+
+    /**
+     * @var MessageInterface|MockObject
+     */
+    private $messageMock;
+
+    /**
+     * @var Collection|MockObject
+     */
+    private $messageCollectionMock;
+
+    protected function setUp(): void
+    {
+        $this->messageCollectionFactoryMock = $this->createMock(MessageCollectionFactory::class);
+        $this->messageCollectionMock = $this->createMock(Collection::class);
+        $this->messageFactoryMock = $this->createMock(MessageFactory::class);
+        $this->messageRepositoryMock = $this->createMock(MessageRepository::class);
+        $this->messageMock = $this->getMockBuilder(MessageInterface::class)
+            ->addMethods(['getJobClass', 'getTarget', 'addData'])
+            ->getMockForAbstractClass();
+
+        $this->instance = new Data(
+            $this->messageCollectionFactoryMock,
+            $this->messageFactoryMock,
+            $this->messageRepositoryMock
+        );
+    }
+
+    /**
+     * Test append jobs
+     *
+     * @dataProvider jobClassesDataProvider
+     * @param string $jobClass
+     * @param mixed $target
+     * @param array $additionalData
+     * @param string $additionalDataEncoded
+     * @return void
+     */
+    public function testAppendJobs(
+        string $jobClass,
+        $target,
+        array $additionalData,
+        string $additionalDataEncoded
+    ): void {
+        $messageQtyFound = 0;
+        $this->messageFactoryMocks($jobClass, $target, $additionalData);
+        $this->messageCollectionMocks($jobClass, $target, $additionalData, $additionalDataEncoded, $messageQtyFound);
+
+        $this->messageRepositoryMock->expects(static::once())
+            ->method('save')
+            ->with($this->messageMock);
+
+        $this->instance->append($jobClass, $target, $additionalData);
+    }
+
+    /**
+     * Test append jobs already queued
+     *
+     * @dataProvider jobClassesDataProvider
+     * @param string $jobClass
+     * @param mixed $target
+     * @param array $additionalData
+     * @param string $additionalDataEncoded
+     * @return void
+     */
+    public function testAppendJobsAlreadyQueued(
+        string $jobClass,
+        $target,
+        array $additionalData,
+        string $additionalDataEncoded
+    ): void {
+        $messageQtyFound = 1;
+        $this->messageFactoryMocks($jobClass, $target, $additionalData);
+        $this->messageCollectionMocks($jobClass, $target, $additionalData, $additionalDataEncoded, $messageQtyFound);
+
+        $this->instance->append($jobClass, $target, $additionalData);
+    }
+
+    /**
+     * Mocks related with message factory
+     *
+     * @param string $jobClass
+     * @param $target
+     * @param array $additionalData
+     * @return void
+     */
+    private function messageFactoryMocks(string $jobClass, $target, array $additionalData): void
+    {
+        $this->messageFactoryMock->expects(static::once())
+            ->method('create')
+            ->willReturn($this->messageMock);
+
+        $this->messageMock->expects(static::once())
+            ->method('addData')
+            ->with(['job_class' => $jobClass, 'target' => $target])
+            ->willReturnSelf();
+
+        $this->messageMock->expects(static::once())
+            ->method('setAdditionalData')
+            ->with($additionalData)
+            ->willReturnSelf();
+    }
+
+    /**
+     * Mocks related with message collection
+     *
+     * @param string $jobClass
+     * @param $target
+     * @param array $additionalData
+     * @param string $additionalDataEncoded
+     * @param int $messageQtyFound
+     * @return void
+     */
+    private function messageCollectionMocks(
+        string $jobClass,
+        $target,
+        array $additionalData,
+        string $additionalDataEncoded,
+        int $messageQtyFound
+    ): void {
+        $this->messageMock->expects(static::once())
+            ->method('getAdditionalData')
+            ->willReturn($additionalData);
+
+        $this->messageCollectionFactoryMock->expects(static::once())
+            ->method('create')
+            ->willReturn($this->messageCollectionMock);
+
+        $this->messageMock->expects(static::once())
+            ->method('getJobClass')
+            ->willReturn($jobClass);
+
+        $this->messageMock->expects(static::once())
+            ->method('getTarget')
+            ->willReturn($target);
+
+        $this->messageCollectionFactoryMock->expects(static::once())
+            ->method('create')
+            ->willReturn($this->messageCollectionMock);
+
+        $this->messageCollectionMock->expects(static::exactly(3))
+            ->method('addFieldToFilter')
+            ->withConsecutive(
+                ['job_class', $jobClass],
+                ['target', $target],
+                ['additional_data', $additionalDataEncoded]
+            )
+            ->willReturnSelf();
+
+        $this->messageCollectionMock->expects(static::once())
+            ->method('count')
+            ->willReturn($messageQtyFound);
+    }
+
+    /**
+     * Provide information to append on message queue
+     *
+     * @return string[][]
+     */
+    public function jobClassesDataProvider(): array
+    {
+        return [
+            [Job::class, 32, ['foo1' => 'bar1'], '{"foo1":"bar1"}'],
+            [Job::class, 43, ['foo2' => 'bar2'], '{"foo2":"bar2"}'],
+            [Job::class, null, [], '[]'],
+            [Job::class, 64, ['foo4' => 'bar4'], '{"foo4":"bar4"}'],
+            [Job::class, null, [], '[]'],
+            [Job::class, 643, ['foo6' => 'bar6'], '{"foo6":"bar6"}']
+        ];
+    }
+}
diff --git a/composer.json b/composer.json
index 5a8ceba..a4106e8 100644
--- a/composer.json
+++ b/composer.json
@@ -8,6 +8,9 @@
         "php": ">=7.2.0 <=7.4.99",
         "discorgento/module-core": "^1.0"
     },
+    "require-dev": {
+        "phpunit/phpunit": "^9"
+    },
     "autoload": {
         "files": [
             "registration.php"