Issue magento#35676 Add Unit tests

Author: Artem Kirkor

app/code/Magento/ImportExport/Test/Unit/Model/Import/Entity/AbstractTest.php

@@ -126,14 +126,29 @@ public function testValidateDataColumnNameWithWhitespaces()
         );
     }
 
+    /**
+     * Test for method validateData()
+     *
+     * @covers \Magento\ImportExport\Model\Import\Entity\AbstractEntity::validateData
+     */
+    public function testValidateColumnName()
+    {
+        $this->_createSourceAdapterMock(['Test_1']);
+        $errorAggregator = $this->_model->validateData();
+        $this->assertArrayNotHasKey(
+            AbstractEntity::ERROR_CODE_COLUMN_NAME_INVALID,
+            $errorAggregator->getRowsGroupedByErrorCode()
+        );
+    }
+
     /**
      * Test for method validateData()
      *
      * @covers \Magento\ImportExport\Model\Import\Entity\AbstractEntity::validateData
      */
     public function testValidateDataAttributeNames()
     {
-        $this->_createSourceAdapterMock(['_test1']);
+        $this->_createSourceAdapterMock(['test.1', '@test']);
         $errorAggregator = $this->_model->validateData();
         $this->assertArrayHasKey(
             AbstractEntity::ERROR_CODE_COLUMN_NAME_INVALID,