[Backport] [Sales] Covering the AssignOrderToCustomerObserver by Unit Test

[eduard13]

Original PR #18490

Description

This PR adds missing unit tests for AssignOrderToCustomerObserver class:

• \Magento\Sales\Observer\AssignOrderToCustomerObserver

Fixed Issues (if relevant)

N/A

Manual testing scenarios

N/A

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[rogyar]

Hi @eduard13. According to the Magento Contributors Guidelines (https://devdocs.magento.com/guides/v2.2/contributor-guide/contributing.html#rules) changes to 2.2-develop branch can be accepted only after they are applied to 2.3-develop branch. Please, consider creating the same PR for 2.3-develop branch. I'm putting this PR on hold in the meanwhile.
Thank you.

[okorshenko]

Hi @eduard13

Thank you for your contribution. We are trying deliver all code cleanups to the latest release line only. For the 2.2 release, it is preferred to deliver only functional improvements and/or bug fixes.

https://devdocs.magento.com/guides/v2.2/contributor-guide/contributing.html#rules

[eduard13]

Hi @okorshenko,
why is this Unit Test a code cleanup? As I can see in the Accepted pull requests and ported code table, the Tests Coverage are also accepted in 2.2. Please correct me if I'm wrong here.
Thank you.

[okorshenko]

Hi @eduard13
This test already exists in 2.2-develop branch. So if you compare your changes and existing test, you will see that your PR just added few blank lines :)

Please see https://github.com/magento/magento2/pull/18559/files