A penetration tester needs to perform a test on a finance system that is PCI...

Quarterly is the minimum frequency to complete the scan of the system that is PCI DSS v3.2.1 compliant, according to Requirement 11.2.2 of the standard1. PCI DSS (Payment Card Industry Data Security Standard) is a set of security standards that applies to any organization that processes, stores, or transmits credit card information. Requirement 11.2.2 states that organizations must perform internal vulnerability scans at least quarterly and after any significant change in the network.

https://www.pcicomplianceguide.o rg/faq/#25

PCI DSS requires quarterly vulnerability/penetration tests, not weekly.