JSON unit tests improvements

[christopher-wild]

Is your feature request related to a problem? Please describe.
The current JSON Frontend unittests rely on the causal test failing for the unittest to pass.

Describe the solution you'd like
A basic casusal DAG and scenario to be made where we know what the test results will be and can test against them. I don't understand the underlying causal inference well enough to make this though.

Describe alternatives you've considered
N/A

Additional context
This would have the benefit of our tests being more accurate. I.e. if a test parameter is not being set correctly but the tests still run, we currently would not know as the tests will just fail as usual.