add some guidance around tests

[mcclurejt]

Resolved Issues

Description

Review Checklists

Please check each item before approving the pull request. While going
through the checklist, it is recommended to leave comments on items that are
referenced in the checklist to make sure that they are reviewed. If there are
multiple reviewers, copy the checklists into sections titled ## [Reviewer Name].
If the PR doesn't touch Solidity, the corresponding checklist can
be removed.

[[Reviewer Name]]

• Tokens
  • Do all approve calls use forceApprove?
  • Do all transfer calls use safeTransfer?
  • Do all transferFrom calls use msg.sender as the from address?
    • If not, is the function access restricted to prevent unauthorized
      token spend?
• Low-level calls (call, delegatecall, staticcall, transfer, send)
  • Is the returned success boolean checked to handle failed calls?
  • If using delegatecall, are there strict access controls on the
    addresses that can be called? It shouldn't be possible to delegatecall
    arbitrary addresses, so the list of possible targets should either be
    immutable or tightly controlled by an admin.
• Reentrancy
  • Are functions that make external calls or transfer ether marked as nonReentrant?
    • If not, is there documentation that explains why reentrancy is
      not a concern or how it's mitigated?
• Gas Optimizations
  • Is the logic as simple as possible?
  • Are the storage values that are used repeatedly cached in stack or
    memory variables?
  • If loops are used, are there guards in place to avoid out-of-gas
    issues?
• Visibility
  • Are all payable functions restricted to avoid stuck ether?
• Math
  • Is all of the arithmetic checked or guarded by if-statements that will
    catch underflows?
  • If Safe functions are altered, are potential underflows and
    overflows caught so that a failure flag can be thrown?
  • Are all of the rounding directions clearly documented?
• Testing
  • Are there new or updated unit or integration tests?
  • Do the tests cover the happy paths?
  • Do the tests cover the unhappy paths?
  • Are there an adequate number of fuzz tests to ensure that we are
    covering the full input space?