[WIP] PLD-2 Applying tests

[SergeyPodgornyy]

Description

Applying unit tests and customize Travis CI

Motivation and context

To achieve 100% Test coverage

How has this been tested?

Tests in progress

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:

Once your pull request is created, it will trigger a build on our continuous integration server to make sure your tests and code style pass.

• I have read the CONTRIBUTING document.
• My pull request addresses exactly one patch/feature.
• I have created a branch for this patch/feature.
• Each individual commit in the pull request is meaningful.
• I have added tests to cover my changes.
• If my change requires a change to the documentation, I have updated it accordingly.

If you're unsure about any of these, don't hesitate to ask. We're here to help!