Kinda depends on what you're doing, how much of Jepsen you're using, and how complex the system-specific code is. You can write a minimal Jepsen test in ~100 lines of code, if that's helpful. Jepsen and its main supporting libraries (Elle and Knossos) clock in at about 19K lines of code; a little over six years of full-time work.
For simulation testing, I'd suggest looking at Maelstrom, which uses Jepsen to provide a sort of workbench for writing toy Raft implementations in any language. You give it a binary which takes messages as JSON on STDIN and emits messages to STDOUT; it spawns a bunch of "nodes" (local processes) of that binary, connects them via a simulated network, generates pathological network behavior, simulates client requests, and verifies the resulting histories with Jepsen.
For simulation testing, I'd suggest looking at Maelstrom, which uses Jepsen to provide a sort of workbench for writing toy Raft implementations in any language. You give it a binary which takes messages as JSON on STDIN and emits messages to STDOUT; it spawns a bunch of "nodes" (local processes) of that binary, connects them via a simulated network, generates pathological network behavior, simulates client requests, and verifies the resulting histories with Jepsen.
https://github.com/jepsen-io/maelstrom