Environment variables

Read by tests and plugins (public contract)

Variable	Value	Meaning
RSTEST_WORKER_ID	gw0, gw1, ...	identity of the worker running this test; unset in -n 0/-n 1 mode
RSTEST_WORKER_COUNT	integer	pool size; unset in -n 0/-n 1 mode
PYTEST_XDIST_WORKER	gw0, gw1, ...	pytest-xdist's env var, set for compatibility — plugins and conftests that grep it work unedited; unset in -n 0/-n 1 mode
PYTEST_XDIST_WORKER_COUNT	integer	xdist's pool-size var, same compatibility contract; unset in -n 0/-n 1 mode
RSTEST_RUN_UID	opaque string	one uid per run, shared by every worker (and every project of a monorepo run); also exposed as workerinput["testrun_uid"]
RSTEST_MONO_PROJECT	relative path	set inside a monorepo child run to that project's path (e.g. libs/core); unset otherwise

Plugins that read pytest-xdist's workerinput get the same information via request.config.workerinput["workerid"] / ["workercount"] / ["testrun_uid"] — that path works under both runners.

Set by the orchestrator (internal)

RSTEST_BASETEMP, RSTEST_SEND_IDS, RSTEST_DOCTOR, RSTEST_WORKER_PATH coordinate workers and may change between versions. Don't depend on them. The orchestrator sets them fresh on every run, so any value you pre-set in the environment is overwritten — no need to scrub them for a hermetic run.

Honored from the environment

Variable	Effect
VIRTUAL_ENV	worker interpreter discovery (first after --python)
NO_COLOR	disables colored output (a forwarded --color=yes/no wins)
PYTEST_ADDOPTS	read by the vendored core, exactly as under pytest
RSTEST_CACHE_DIR	base dir for the interpreter-probe cache only (<dir>/rstest/interp-probes-v1.json), which speeds up repeated --python version resolution. It does not relocate .rstest_cache/ (durations/flakes) — that always lives in the invocation directory. Defaults to $XDG_CACHE_HOME (or ~/.cache) on Unix and %LOCALAPPDATA% on Windows; if none resolve, probing just isn't persisted
RSTEST_FLAKE_RETENTION_DAYS	how long a test's flake/failure history (.rstest_cache/flakes.json) stays relevant. A test with no flake or failure inside this window reads as fixed: its entry is dropped and it stops carrying "flaked _N_x before" annotations. Defaults to 90; 0 keeps history forever