A flaky test is an unreliable software test that sometimes passes and sometimes fails for the same code. Flaky tests are problematic because they reduce confidence in the test suite and make it difficult to determine if a failure represents an actual regression. Flaky tests are one type of test within a software test suite that shows instability. In contrast, well-known tests that unconditionally pass or fail by the status of the system under test, flaky tests are the exact opposite. They fluctuate in their outcomes when they are performed under identical circumstances. This rationale poses a great difficulty for the integrity of the testing process, moreover, it weakens the confidence in the testing results.
Characteristics of Flaky Tests
Flaky tests possess distinct characteristics that set them apart from stable tests. These include:
Sensitive to Execution Environment: Highly unstable tests differ about the execution environment including its operating system, a software version, or a system configuration, and are therefore rather inefficient and create more or less inconsistent outcomes as a result of eminent deviations.
Inconsistent Across Platforms: For instance, flaky tests may show different results on various platforms/hardware or show preferences for certain platforms, implying that platform-dependent incompatibilities have an impact on test reliability.
Dependence on External Services: Flaky Tests, arising from dependencies against external providers like databases or APIs, get overwhelmed by inconsistency because of unavailability, slow response, or behavioral variations of these providers.
Timing Sensitivity: The errors in the tests that include asynchronous processes or timing problems may happen because of the period when the execution is splitting time or when the operation is combined.
Intermittent Network Issues: The testing or running of applications that are interacting with network resources can occasionally be affected by network problems such as packet loss or bursts of latency can increase the variation in the results.
Race Conditions: Flakey tests with race conditions, are non-deterministic, and bypass or fail unpredictably, this is because the timing of overlapping operations may have a dominant effect.
Non-reproducible Failures: Some flaky tests may fail and backtrack which is a tough job to solve, reproducing bugs and diagnosing them.
Unpredictable Error Reporting: Erroneous versions of flaky tests may offer indirect error reports or climbs when they fail. This may lead to the failure to identify the source of problems and subsequent handling of the complaints.