Fixed several issues related to the code quality

[marci4]

Description

Extended tests
Less complexity in some methods

Related Issue

#749

Motivation and Context

Less complexity in some methods

How Has This Been Tested?

Autotests

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.