diff --git a/app/code/Magento/InventoryImportExport/Model/Import/Command/Append.php b/app/code/Magento/InventoryImportExport/Model/Import/Command/Append.php
index 51ae14440a591..530fcce22a68a 100644
--- a/app/code/Magento/InventoryImportExport/Model/Import/Command/Append.php
+++ b/app/code/Magento/InventoryImportExport/Model/Import/Command/Append.php
@@ -5,6 +5,7 @@
  */
 
 namespace Magento\InventoryImportExport\Model\Import\Command;
+
 use Magento\InventoryApi\Api\Data\SourceItemInterface;
 use Magento\InventoryApi\Api\Data\SourceItemInterfaceFactory;
 use Magento\InventoryApi\Api\SourceItemsSaveInterface;
diff --git a/app/code/Magento/InventoryImportExport/Model/Import/Command/CommandInterface.php b/app/code/Magento/InventoryImportExport/Model/Import/Command/CommandInterface.php
index efc9b5cb05b56..7bb5a73bed0a4 100644
--- a/app/code/Magento/InventoryImportExport/Model/Import/Command/CommandInterface.php
+++ b/app/code/Magento/InventoryImportExport/Model/Import/Command/CommandInterface.php
@@ -7,11 +7,15 @@
 namespace Magento\InventoryImportExport\Model\Import\Command;
 
 /**
+ * It is extension point to implement import/export functionality (Service Provider Interface - SPI)
+ *
  * @api
  */
 interface CommandInterface
 {
     /**
+     * Executes the current command.
+     *
      * @param array $bunch
      * @return void
      * @throws CommandException
diff --git a/app/code/Magento/InventoryImportExport/Model/Import/Serializer/Json.php b/app/code/Magento/InventoryImportExport/Model/Import/Serializer/Json.php
index 2a9b52bf8a39d..0a56563488e89 100644
--- a/app/code/Magento/InventoryImportExport/Model/Import/Serializer/Json.php
+++ b/app/code/Magento/InventoryImportExport/Model/Import/Serializer/Json.php
@@ -22,9 +22,8 @@ class Json implements SerializerInterface, LegacyJsonHelperInterface
      * Json constructor.
      * @param SerializerInterface $serializer
      */
-    public function __construct(
-        SerializerInterface $serializer
-    ) {
+    public function __construct(SerializerInterface $serializer)
+    {
         $this->serializer = $serializer;
     }
 
diff --git a/app/code/Magento/InventoryImportExport/Model/Import/Validator/SourceValidator.php b/app/code/Magento/InventoryImportExport/Model/Import/Validator/SourceValidator.php
index c8644464d4e8a..efbce923cddcd 100644
--- a/app/code/Magento/InventoryImportExport/Model/Import/Validator/SourceValidator.php
+++ b/app/code/Magento/InventoryImportExport/Model/Import/Validator/SourceValidator.php
@@ -6,7 +6,6 @@
 
 namespace Magento\InventoryImportExport\Model\Import\Validator;
 
-use Magento\Framework\Exception\LocalizedException;
 use Magento\Framework\Validation\ValidationResultFactory;
 use Magento\InventoryApi\Api\SourceRepositoryInterface;
 use Magento\InventoryImportExport\Model\Import\Sources;
@@ -63,16 +62,19 @@ public function validate(array $rowData, $rowNumber)
     }
 
     /**
+     * Returns exits already the source in sources.
+     *
      * @param int $sourceId
      * @return bool
      */
-    private function isExistingSource($sourceId)
+    private function isExistingSource($sourceId): bool
     {
         return isset($this->sourceIds[$sourceId]);
     }
 
     /**
      * Loads all existing source ids
+     *
      * @return void
      */
     private function loadSourceIds()
diff --git a/app/code/Magento/InventoryImportExport/Model/Import/Validator/ValidatorChain.php b/app/code/Magento/InventoryImportExport/Model/Import/Validator/ValidatorChain.php
index 537f4abed6794..d93fb69bc5a22 100644
--- a/app/code/Magento/InventoryImportExport/Model/Import/Validator/ValidatorChain.php
+++ b/app/code/Magento/InventoryImportExport/Model/Import/Validator/ValidatorChain.php
@@ -10,9 +10,7 @@
 use Magento\Framework\Validation\ValidationResultFactory;
 
 /**
- * Extension point for row validation
- *
- * @api
+ * @inheritdoc
  */
 class ValidatorChain implements ValidatorInterface
 {
@@ -52,14 +50,16 @@ public function __construct(
      */
     public function validate(array $rowData, $rowNumber)
     {
-        $errors = [];
+        /* the inner empty array covers cases when no loops were made */
+        $errors = [[]];
         foreach ($this->validators as $validator) {
             $validationResult = $validator->validate($rowData, $rowNumber);
 
             if (!$validationResult->isValid()) {
-                $errors = array_merge($errors, $validationResult->getErrors());
+                $errors[] = $validationResult->getErrors();
             }
         }
-        return $this->validationResultFactory->create(['errors' => $errors]);
+
+        return $this->validationResultFactory->create(['errors' => array_merge(...$errors)]);
     }
 }
diff --git a/app/code/Magento/InventoryImportExport/Model/Import/Validator/ValidatorInterface.php b/app/code/Magento/InventoryImportExport/Model/Import/Validator/ValidatorInterface.php
index defc1f64c1dba..0e52ccddac444 100644
--- a/app/code/Magento/InventoryImportExport/Model/Import/Validator/ValidatorInterface.php
+++ b/app/code/Magento/InventoryImportExport/Model/Import/Validator/ValidatorInterface.php
@@ -9,7 +9,7 @@
 use Magento\Framework\Validation\ValidationResult;
 
 /**
- * Extension point for row validation
+ * Extension point for row validation (Service Provider Interface - SPI)
  *
  * @api
  */
diff --git a/app/code/Magento/InventoryImportExport/Test/Unit/Model/ValidatorChainTest.php b/app/code/Magento/InventoryImportExport/Test/Unit/Model/ValidatorChainTest.php
new file mode 100644
index 0000000000000..fe739c5deaef1
--- /dev/null
+++ b/app/code/Magento/InventoryImportExport/Test/Unit/Model/ValidatorChainTest.php
@@ -0,0 +1,127 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Inventory\Test\Unit\Model;
+
+use Magento\Framework\TestFramework\Unit\Helper\ObjectManager;
+use Magento\Framework\Validation\ValidationResultFactory;
+use Magento\InventoryImportExport\Model\Import\Validator\ValidatorChain;
+use Magento\InventoryImportExport\Model\Import\Validator\ValidatorInterface;
+use PHPUnit\Framework\TestCase;
+
+class ValidatorChainTest extends TestCase
+{
+
+    /**
+     * @var ValidatorInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $qtyValidator;
+
+    /**
+     * @var ValidatorInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $skuValidator;
+
+    /**
+     * @var ValidationResultFactory|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $validationResultFactory;
+
+    /**
+     * @var ValidatorChain
+     */
+    private $validatorChain;
+
+    /**
+     * @inheritdoc
+     */
+    protected function setUp()
+    {
+        $this->validationResultFactory = $this->getMockBuilder(ValidationResultFactory::class)->getMock();
+        $this->qtyValidator = $this->getMockBuilder(ValidatorInterface::class)->getMock();
+        $this->skuValidator = $this->getMockBuilder(ValidatorInterface::class)->getMock();
+    }
+
+    public function testValidateWithOutValidators()
+    {
+        $emptyValidatorResult = $this->createMock(\Magento\Framework\Validation\ValidationResult::class);
+        $this->validationResultFactory->expects($this->once())
+            ->method('create')
+            ->with(['errors' =>[]])
+            ->willReturn($emptyValidatorResult);
+
+        $this->validatorChain = (new ObjectManager($this))->getObject(
+            ValidatorChain::class,
+            [
+                'validationResultFactory' => $this->validationResultFactory,
+                'validators' => []
+            ]
+        );
+
+
+        $result = $this->validatorChain->validate([], 1);
+        $this->assertEquals($emptyValidatorResult, $result);
+    }
+
+    public function testValidateWithOutErros()
+    {
+        $emptyValidatorResult = $this->createMock(\Magento\Framework\Validation\ValidationResult::class);
+        $emptyValidatorResult->expects($this->once())->method('isValid')
+            ->willReturn(true);
+
+        $this->validationResultFactory->expects($this->once())
+            ->method('create')
+            ->with(['errors' => []])
+            ->willReturn($emptyValidatorResult);
+
+        $this->qtyValidator->method('validate')
+            ->willReturn($emptyValidatorResult);
+
+        $this->validatorChain = (new ObjectManager($this))->getObject(
+            ValidatorChain::class,
+            [
+                'validationResultFactory' => $this->validationResultFactory,
+                'validators' => [$this->qtyValidator]
+            ]
+        );
+
+        $result = $this->validatorChain->validate([], 1);
+        $this->assertEquals($emptyValidatorResult, $result);
+    }
+
+
+    public function testValidateWithErros()
+    {
+        $validatorResult = $this->createMock(\Magento\Framework\Validation\ValidationResult::class);
+
+        $validatorResult->expects($this->once())->method('isValid')
+            ->willReturn(false);
+
+        $validatorResult->expects($this->once())
+            ->method('getErrors')
+            ->willReturn(['Qty can not negative', 'Additional error']);
+
+        $this->qtyValidator->expects($this->once())->method('validate')
+            ->willReturn($validatorResult);
+
+        $this->validationResultFactory->expects($this->once())
+            ->method('create')
+            ->with(['errors' => ['Qty can not negative', 'Additional error']])
+            ->willReturn($validatorResult);
+
+
+        $this->validatorChain = (new ObjectManager($this))->getObject(
+            ValidatorChain::class,
+            [
+                'validationResultFactory' => $this->validationResultFactory,
+                'validators' => [$this->qtyValidator]
+            ]
+        );
+
+        $result = $this->validatorChain->validate([-1], 1);
+        $this->assertEquals($validatorResult, $result);
+    }
+}