Hey Mark,

You should at least test against the Solution but potentially both.  A project transitions from Requirements Elicitation to Solutioning to Development/Coding.

When first gathering requirements, the solution is left undefined since there exists many ways to satisfy a requirement.  However, once the solutioning begins and the client signs off then that is what the coders should be working towards.

In an ideal world you would only test against the signed off solution.  The assumption is that before the sign-off of the Solution Document someone (client, analyst, whoever) has ensured that it met all  requirements. But this step may not have occurred.  A good analyst will determine if a requirement was missed, work to assess whether it was intentional (e.g., conversations occurred and it was deemed unnecessary), and if it was missed in error then take the necessary steps to figure out what should be done.