Assert vote contents in WriteRef tests

WriteRef tests currently assert only the number of votes expected. This isn't sufficient to test that the voting logic is behaving correctly as the votes could still be in wrong order, in the wrong phase or have the wrong content. When integrating the WAL, this makes it difficult to determine whether the voting behaves still the same or not. This commit asserts the complete vote content to ensure the test catches actual regressions in the voting logic.

Related to #5147