provide unit tests and coverage

[fulls1z3]

I'm submitting a ... (check one with "x")

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  <!-- Please check the repository for a similar issue or PR before submitting -->
[ ] Support request => <!-- Please check the repository for a similar issue or PR before submitting -->
[x] Feature request
[ ] Documentation issue or request

Current behavior

Expected/desired behavior

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

Environment

• Angular version: X.Y.Z

• Browser:

• Chrome (desktop) version XX
• Chrome (Android) version XX
• Chrome (iOS) version XX
• Firefox version XX
• Safari (desktop) version XX
• Safari (iOS) version XX
• IE version XX
• Edge version XX

• For Tooling issues:

• Node version: XX
• Platform:

• Others: