No one can see mold spores. Testing is the only way to know if your job is completed successfully.
You’ve gone through a lot to get your project to this point. Doesn’t it make sense to test before you rebuild?
Mold post remediation validation is testing with a report that says the mold cleanup was successful. Occasionally, additional cleanup work may be needed. After that cleanup, more testing should typically be done.
Of course, there is a visual inspection. If daylight is seen inside the cleaned area, then rain can also get inside. Toxic mold can regrow after cleaning if the water leaks or sources of water intrusions aren’t fixed before interior reconstruction begins.
After any remedial work, post mold remediation validation or clearance testing with a report is always recommended. This testing should be done with engineering controls and containment still in place, to prevent possible cross contamination.
Mold cleanup normally should be done by professionals, not your general contractor, handyman or friends.
See Contractors that do this type of work.