test: refactor unit_test.py (#377)

* test: refactor upto references

* tests: refactor docstring extractor

* tests: refactor upto packages

* test: refactors for parsing docstring summary

* tests: finished refactoring test_unit.py

* test: update typos

* test: move the explanation comment up

* test: refactor to use test paramters

* test: refactor rest of tests into similar format