Import data for existing simple product, type "Stock Sources", import behavior "Add/Update"

Preconditions
Magento with MSI module
Simple product with Sku "sku1" and Stock Quantity = 100 and Qty on Default Source = 100 created

Steps to reproduce

1. Create .csv file for import with source_id = 1, sku = sku1, status = 1 and quantity = 10
2. Goto Admin -> System -> Import
3. Select "Import Type" = Stock Sources
4. Select "Import Behavior" = Add/Update
5. Click on "Choose File" button in "Select File to Import" field and navigate to your .csv import file in your system
6. Click on "Check Data" button
7. If you got success message "File is valid! To start import process press "Import" button" - press "Import" button
8. Success message 'Import successfully done" appear
9. Navigate to Admin -> Catalog -> Products and open product page of your Simple Product "sku1"
10. Verify that in "Assigned Sources" field Qty on Default Source is updated to "10" and Quantity in Stock of this product is the same