Refactor test #33
Description
Tests are placed in one file and all of them are integrational. There are many duplications here because of this.
- Create unit tests for internal classes.
- Remove redundant integration test cases (part of them should be replaced by unit tests for internal classes).
- Move integrational and unit tests to separate files.
- Use matchers for value comparison.
- Create separate classes for each test case/group to isolate tests.