Fixing Flaky Tests Camunda 8.8 UnassignUserTaskMigrationIT

Hey guys! Today, we're diving deep into a flaky test issue we encountered in Camunda 8.8, specifically within the UnassignUserTaskMigrationIT integration test. This article will walk you through the problem, its root cause, and the solution we're implementing to make our tests more reliable. Let's jump right in!

The Issue: Intermittent Failures in UnassignUserTaskMigrationIT

So, the main problem we've been seeing is that the test UnassignUserTaskMigrationIT#shouldUnAssign88JobWorkerV1(CamundaMigrator) has been failing intermittently. If you check out this dashboard link, you can see the failure history. The test's purpose is to unassign a user task using the Tasklist V1 API. However, the unassign operation sometimes gets rejected with a 400 Bad Request error, specifically the TASK_IS_NOT_ACTIVE error. This basically means that the system thinks the task isn't in a state where it can be unassigned yet.

This happens because the task might still be in a transitional state, like CREATING or ASSIGNING, when the unassign request is sent. The Tasklist unassigned endpoint expects the task to be in a CREATED state before it can process the unassignment. This discrepancy leads to the flaky behavior we're seeing. It's like trying to return a package to the sender before the delivery service has finished registering it in the system – the system will say, “Hey, I don’t know about this package yet!”

To reproduce this issue, you simply need to run the UnassignUserTaskMigrationIT#shouldUnAssign88JobWorkerV1 test multiple times. You'll notice that if the unassign request is sent too soon after the task is imported, it fails. The test attempts to unassign the task almost immediately after it’s imported. If the task hasn't fully transitioned to the CREATED state, the test throws a 400 error. The current behavior we observe is a test failure with the following error message:

expected: 200
but was: 400
...
InvalidRequestException: { "title": "TASK_IS_NOT_ACTIVE", "detail": "Task is not active" }

Ideally, the test should wait for the task to reach the CREATED state before attempting the unassign operation. This will prevent the race condition that causes the flaky failures. The expected behavior is that the test should consistently pass, because it only attempts to unassign a task once that task is fully in the correct state and ready for such an action. By ensuring the task is in the CREATED state, we avoid the timing issues that lead to intermittent failures. So we need to make sure our test is a little more patient and doesn't jump the gun before the task is ready for unassignment!

Root Cause Analysis: Why is This Happening?

The root cause of this flakiness lies in the test's use of the waitFor88TaskToBeImportedReturningId method. This method is designed to return as soon as any task associated with the correct process instance is imported, without considering the task's current lifecycle state. So, the test might receive the task ID while the task is still in the process of being created or assigned, which means it hasn’t reached the CREATED state yet.

Think of it like this: imagine you're waiting for a pizza to be delivered. waitFor88TaskToBeImportedReturningId is like getting a notification that the pizza order has been placed, but that doesn't mean the pizza is ready to eat! It might still be in the oven, being topped with cheese, or waiting for the delivery driver. Similarly, the task might be in the process of being created or assigned when the test receives the task ID. Therefore, when the test tries to unassign the task, it's like trying to eat the pizza before it's even baked – it's just not ready yet.

This premature action leads to the 400 Bad Request error because the Tasklist unassigned endpoint expects the task to be in a specific, stable state (CREATED) before allowing unassignment. The test essentially acts too quickly, issuing the unassign request before the task has fully transitioned into the required state. The timing mismatch between the task's lifecycle and the test's actions is the core of the problem. It highlights the need for a more precise waiting mechanism that accounts for the task’s state before proceeding with subsequent operations.

The Solution: Waiting for the CREATED State

To address this issue, the solution is to modify the waitFor88TaskToBeImportedReturningId method to explicitly wait for a task in the CREATED state. This ensures that the test only attempts to unassign the task when it's actually ready for unassignment. By waiting for this specific state, we eliminate the race condition and make the test more reliable.

This is akin to telling our pizza delivery tracker to not only notify us when the order is placed but also to send a second notification when the pizza is out of the oven and on its way. This way, we know the pizza is actually ready to be enjoyed when we get the notification. Similarly, by waiting for the CREATED state, we guarantee that the task is fully ready before we try to unassign it. This approach not only fixes the immediate flakiness in UnassignUserTaskMigrationIT but also improves the robustness of other tests that rely on waitFor88TaskToBeImportedReturningId. These other tests could potentially be facing similar timing issues without us even realizing it. Waiting for the CREATED state makes our testing strategy more robust and consistent across the board.

By making this change, we're preventing the test from rushing ahead and attempting actions on tasks that are not yet in the correct state. This ensures that the test aligns its actions with the actual state transitions of the task, which is crucial for reliable testing.

Dev -> QA Handover

Alright, let's talk about the handover from development to quality assurance (QA). This is a crucial step to make sure everything works smoothly. Here’s what we need to consider:

• Resources: We need to provide the updated code, including the modified waitFor88TaskToBeImportedReturningId method, along with clear instructions on how to run the test and verify the fix. Think of it as handing over the keys to the new and improved pizza-delivery system.
• Versions to Validate: QA should validate this fix on the Camunda 8.8-SNAPSHOT version, as this is where the issue was initially identified. It's important to confirm that the changes resolve the flakiness in the UnassignUserTaskMigrationIT test and don't introduce any regressions.
• Release Version: This fix will be included in a future release of Camunda 8.8. We need to communicate this clearly so that users know when to expect the improved test stability. It will be like announcing the availability of the improved pizza-delivery tracking system to all our customers!

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Conclusion

So, there you have it! We've walked through the flaky test issue in Camunda 8.8, understood the root cause, and outlined the solution. By modifying the waitFor88TaskToBeImportedReturningId method to wait for the CREATED state, we're making our tests more reliable and robust. This fix ensures that we're testing the system in a way that accurately reflects its behavior, leading to more confident releases and a better overall experience for our users. Keep an eye out for this fix in an upcoming Camunda 8.8 release, and let us know if you have any questions or feedback!