Optimise test framework.

[OGKevin]

Steps to reproduce:

1. Try and execute tests

What should happen:

1. It should be easy and fast

What happens:

1. It is hard to set up and can take up to 10 mins to complete.

Traceback

SDK version and environment

• Tested on 0.12.4
• Sandbox
• Production

Response id

• Response id:

Extra info:

Reference: bunq/sdk_php#120