Ensure fx serve is running for your device.
Ensure fx set is configured --with //src/lib/mapped-clock/benchmarks:pkg, or if you already have a fx set setup, then append to args.gn:
local_bench = true developer_test_labels += ["//src/lib/mapped-clock/benchmarks:pkg"]
fx ffx test run fuchsia-pkg://fuchsia.com/mapped_clock_benchmarks#meta/mapped_clock_benchmarks.cm
See the output in the ffx test results on your terminal.