Refactor tests to reduce duplication

[holly-cummins]

At the moment, for both provider and consumer, the tests have the test methods and sample code duplicated 2-4 times. For example, the test methods are in a normal mode deployment test, a dev mode deployment test, a normal mode integration test, and a dev mode integration test.

We should be able to reduce this duplication. Inheritance is an obvious option, but may not be the right one, for the reasons described in https://www.petrikainulainen.net/programming/unit-testing/3-reasons-why-we-should-not-use-inheritance-in-our-tests/ and https://medium.com/decisionbrain/factor-test-code-the-junit-5-way-that-is-without-inheritance-9ba2784d34 - but annotations might significantly affect the running of the tests, given that annotations are a major cause of problems in this context. So it needs thought.