Have you encountered situations where tests unexpectedly stop passing without obvious reasons?

Yes, such situations occur and are often related to changes in the environment or code that are not immediately obvious:

• Changes in dependencies (libraries, framework versions).
• Changes in data or the state of the test environment.
• Parallel execution of tests affecting the state.
• Synchronization or timing issues (e.g., asynchronous operations).
• External factors: network, database access, environment configuration.

For diagnosis, it is helpful to use logs, isolate tests, record dependency versions, and apply stable test data.