Ensuring bounded end-to-end latency and high reliability is essential for time-critical services, motivating the development of TSN and DetNet protocols to guarantee predictable and reliable network performance. Testing the performance of IEEE and IETF standards can be challenging due to the cost of commercial devices supporting their implementation. In this work, we present TFTG, a traffic generator based on Tofino capable of creating TSN and DetNet traffic with nanoscale precision and high throughput. The proposed solution can be used in different scenarios to test standards for synchronization, reliability, and scheduling, with high flexibility in its applications. With these functionalities, TFTG serves as an open-source solution that users can employ to test target device capabilities, abstracting different topologies and scenarios for multiple protocols and testbed configurations.