Flaky tests

Flaky tests are those that have different outcomes during different runs, i.e. they are not deterministic. To combat these, acton test will per default attempt to run tests multiple times to ensure that the result is the same. It runs as many test iterations as possible for at least 50ms. If a test is flaky, this will be displayed in the test output.


import random
import testing

def _test_flaky():
    i = random.randint(0, 2)
    if i == 0:
    elif i == 1:
        testing.assertEqual(1, 2)
        raise ValueError("Random failure")


acton test


Building project in /home/user/foo
  Compiling example.act for release
   Finished compilation in   0.017 s
  Final compilation step
   Finished final compilation step in   0.453 s

Tests - module example:
  flaky:                 FLAKY FAIL: 565 failures out of 1140 runs in 50.043ms
    testing.NotEqualError: Expected equal values but they are non-equal. A: 1 B: 2

1 out of 1 tests failed (0.625s)