Network testing using a programmable packet engine

Embodiments described herein describe a network tester that is configured to perform packet modification at an egress pipeline of a programmable packet engine. A packet stream is received at an egress pipeline of an output port of the programmable packet engine, wherein the output port includes a packet modifier. Packets of the packet stream are modified at the packet modifier. The packet stream including modified packets is transmitted through an egress pipeline of the output port.