Slow tests and timeouts¶
Slow tests can bottleneck your test run. Nextest identifies tests that take more than a certain amount of time, and optionally lets you terminate tests that take too long to run.
Slow tests¶
For tests that take more than a certain amount of time (by default 60 seconds), nextest prints out a SLOW status. For example, in the output below, test_slow_timeout takes 90 seconds to execute and is marked as a slow test.
Starting 4 tests across 2 binaries (19 skipped; run ID: e55650c7-c8dc-4c4d-b3fc-ebb8f0c3fd55, nextest profile: default)
PASS [ 0.005s] nextest-tests::basic tests::test_success
PASS [ 0.006s] nextest-tests::basic tests::test_success_should_panic
PASS [ 0.006s] nextest-tests::other tests::other_test_success
SLOW [> 60.000s] nextest-tests::basic tests::test_slow_timeout
PASS [ 90.001s] nextest-tests::basic tests::test_slow_timeout
------------
Summary [ 90.002s] 4 tests run: 4 passed (1 slow), 19 skipped
SLOW [ 90.001s] nextest-tests::basic tests::test_slow_timeout
Starting 4 tests across 2 binaries (19 skipped; run ID: e55650c7-c8dc-4c4d-b3fc-ebb8f0c3fd55, nextest profile: default)
PASS [ 0.005s] nextest-tests::basic tests::test_success
PASS [ 0.006s] nextest-tests::basic tests::test_success_should_panic
PASS [ 0.006s] nextest-tests::other tests::other_test_success
SLOW [> 60.000s] nextest-tests::basic tests::test_slow_timeout
PASS [ 90.001s] nextest-tests::basic tests::test_slow_timeout
------------
Summary [ 90.002s] 4 tests run: 4 passed (1 slow), 19 skipped
SLOW [ 90.001s] nextest-tests::basic tests::test_slow_timeout
Configuring timeouts¶
To customize how long it takes before a test is marked slow, use the slow-timeout configuration parameter. For example, to set a timeout of 2 minutes before a test is marked slow, add this to .config/nextest.toml:
[profile.default]
slow-timeout = "2m"
Nextest uses the humantime parser: see its documentation for the full supported syntax.
Terminating tests after a timeout¶
Nextest lets you optionally specify a number of slow-timeout periods after which a test is terminated. For example, to configure a slow timeout of 30 seconds and for tests to be terminated after 120 seconds (4 periods of 30 seconds), add this to .config/nextest.toml:
[profile.default]
slow-timeout = { period = "30s", terminate-after = 4 }
Example¶
The run below is configured with:
slow-timeout = { period = "1s", terminate-after = 2 }
Starting 4 tests across 2 binaries (19 skipped; run ID: 6a8d9aee-4544-47b2-ada2-d5335c74c18b, nextest profile: default)
PASS [ 0.005s] nextest-tests::basic tests::test_success
PASS [ 0.006s] nextest-tests::basic tests::test_success_should_panic
PASS [ 0.006s] nextest-tests::other tests::other_test_success
SLOW [> 1.000s] nextest-tests::basic tests::test_slow_timeout
TERMINATING [> 2.000s] nextest-tests::basic tests::test_slow_timeout
TIMEOUT [ 2.001s] nextest-tests::basic tests::test_slow_timeout
------------
Summary [ 2.002s] 4 tests run: 4 passed (1 slow), 19 skipped
TIMEOUT [ 2.001s] nextest-tests::basic tests::test_slow_timeout
Starting 4 tests across 2 binaries (19 skipped; run ID: 6a8d9aee-4544-47b2-ada2-d5335c74c18b, nextest profile: default)
PASS [ 0.005s] nextest-tests::basic tests::test_success
PASS [ 0.006s] nextest-tests::basic tests::test_success_should_panic
PASS [ 0.006s] nextest-tests::other tests::other_test_success
SLOW [> 1.000s] nextest-tests::basic tests::test_slow_timeout
TERMINATING [> 2.000s] nextest-tests::basic tests::test_slow_timeout
TIMEOUT [ 2.001s] nextest-tests::basic tests::test_slow_timeout
------------
Summary [ 2.002s] 4 tests run: 4 passed (1 slow), 19 skipped
TIMEOUT [ 2.001s] nextest-tests::basic tests::test_slow_timeout
How nextest terminates tests¶
On Unix platforms, nextest creates a process group for each test. On timing out, nextest attempts a graceful shutdown: it first sends the SIGTERM signal to the process group, then waits for a grace period (by default 10 seconds) for the test to shut down. If the test doesn't shut itself down within that time, nextest sends SIGKILL (kill -9) to the process group to terminate it immediately.
To customize the grace period, use the slow-timeout.grace-period configuration setting. For example, with the ci profile, to terminate tests after 5 minutes with a grace period of 30 seconds:
[profile.ci]
slow-timeout = { period = "60s", terminate-after = 5, grace-period = "30s" }
To send SIGKILL to a process immediately, without a grace period, set slow-timeout.grace-period to zero:
[profile.ci]
slow-timeout = { period = "60s", terminate-after = 5, grace-period = "0s" }
0.9.61 The slow-timeout.grace-period setting is also applied to terminations due to Ctrl-C or other signals. With older versions, nextest always waits 10 seconds before sending SIGKILL.
Termination on Windows¶
On Windows, nextest terminates the test immediately in a manner akin to SIGKILL. (On Windows, nextest uses job objects to kill the test process and all its descendants.) The slow-timeout.grace-period configuration setting is ignored.
Per-test overrides¶
Nextest supports per-test overrides for the slow-timeout and terminate-after settings.
For example, some end-to-end tests might take longer to run and sometimes get stuck. For tests containing the substring test_e2e, to configure a slow timeout of 120 seconds, and to terminate tests after 10 minutes:
[[profile.default.overrides]]
filter = 'test(test_e2e)'
slow-timeout = { period = "120s", terminate-after = 5 }
See Override precedence for more about the order in which overrides are evaluated.