An approval process selects eligible records, assigns an approver, and applies different actions for approval and rejection. Locking can protect a pending record from ordinary edits. The process must still leave a usable outcome when the approver rejects the request.
Test both branches. A pending request that looks correct says nothing about the final field updates, and the requester must not impersonate the assigned approver. Entry criteria should identify the business exception without sending every routine record for review. Keep approval separate from a field merely called Approved. A checkbox alone doesn't record who made the decision or whether the process's requirements were met. The local simulator stores a request and enforces the configured active approver.