Mock the integration tests which currently rely on real data

[simon-20]

Brief Description
Some of the integration tests use real data, making a connection to the Datastore (dev or production, depending on which test collection one runs). This means they are subject to failing, if either the identifiers which are tested existence of are removed by the publisher (I used a publisher with a policy of never unpublishing activities, but the risk remains), or if someone were to publish an activity with the identifier of the test activities (very unlikely, but possible).

Initial task is to work how much work it would be to mock the relevant tests.