Structure the common test data

[altaywtf]

Description

The current state of our test files is a little bit messy in terms of using the fixtures. In order to avoid repetition and have a well-defined example dataset, it'd be nice to invest some time on refactoring our tests.

Motivation

• Decrease repetition
• Use a more structured and accurate example data
• Increase the speed of adding new tests to the codebase