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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11If a test suite starts failing after its execution order changes, the order may have exposed a dependency between tests—but that alone does not prove the cause. The title gives no runner, version, configuration change, or failure output, so the incident cannot be diagnosed from the test count alone. Compare the old and new sequences, then reproduce the failures under controlled conditions.
Why did tests fail when the runner changed their order?
A test is order-dependent when it passes in at least one execution order and fails in another. The changed sequence is a useful diagnostic clue: a test may be relying on state left behind by an earlier test, or on cleanup that did not happen. It is not, by itself, proof that order caused these 37 failures—or that all 37 share one cause.
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The distinction matters. A runner update or configuration change could coincide with a separate problem, and the title does not identify what changed. The 2019 paper “iFixFlakies: A Framework for Automatically Fixing Order-Dependent Flaky Tests” uses passing in one order and failing in another as the defining behavior for this category. That definition helps frame the investigation; the paper does not establish what happened in this incident.
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Before changing the suite, preserve the failure output and record the conditions for both the last passing run and the first failing run. Identify:
- The test runner and its version.
- The exact command, options, and plugins used locally and in CI.
- Any runner, plugin, configuration, or CI change between the two runs.
- The individual failing tests and their complete error output.
- The environment and inputs, including relevant services and test data.
The test count in the title is the incident premise, not an independently verified statistic. Without these details, it is not possible to say whether a runner changed order, why the failures appeared, or whether they have a common cause.
Compare the old and new execution sequences
Capture the collection or verbose output from each run if the runner provides it. Compare the sequences around each failure and look for explicit randomization, parallel execution, a failed-tests-first option, or changes to test discovery. Keep the full order as well as the failing-test list: the tests immediately before a failure may be relevant.
One concrete example is pytest’s --failed-first option. Its stable API reference says it runs all tests with previous failures first and warns, “This may re-order tests and thus lead to repeated fixture setup/teardown.” That is an example of a setting that can alter order, not evidence that pytest or this option was involved here. See the pytest API reference.
Reproduce the failure, then narrow the dependency
- Repeat the changed run. Keep the command, environment, and inputs consistent with the failing run. If the runner supports a random seed, record and reuse it so the sequence can be reproduced.
- Run each failing test alone. A test that passes alone but fails in the suite is a reason to investigate interactions; it is not yet proof of which earlier test is responsible.
- Add likely predecessors. Run the failing test with tests that appeared before it in the failing sequence, adding them in manageable groups until the failure appears. Then narrow the group to identify the smallest reproducible combination.
- Check plausible shared resources. Inspect process-level state, databases, files and temporary directories, environment variables, clocks, network services, and teardown behavior. Treat these as hypotheses to test, not established causes.
Runner-specific commands vary by tool and version. The pytest documentation index links to guidance on flaky tests and pytest features, but it should not be read as evidence about an unidentified runner or configuration.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Fix the dependency, then verify the suite
Once a dependency is identified, make each test’s setup explicit and its cleanup complete where practical. A test should not require another test to create data, set a process variable, leave a file behind, or perform teardown on its behalf.
Do not treat restoring the old fixed order as the durable fix. Pinning an order may serve as temporary containment if a specific CI constraint requires it, but it can hide the dependency and leave the suite vulnerable to another ordering change. After a repair, verify the formerly failing tests both in isolation and in the full suite under more than one order. Until those runs succeed, the fix is not verified.
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