A flaky test is a test that sometimes passes and sometimes fails, without any changes to the code under test. Flaky tests can be caused by a number of factors, including:
- Race conditions
- Timing issues
- Dependencies on external resources (e.g. a database)
- Inconsistent test data
Flaky tests can be very frustrating for developers, as they can make it difficult to determine whether a failure is due to a real bug or just a flaky test. In some cases, flaky tests can even cause false positives, where a test appears to be passing when it actually isn't.
There are a few ways to deal with flaky tests, including:
- Fixing the underlying issues that are causing the tests to be flaky
- Ignoring flaky tests (e.g. by marking them as "known issues")
- Disabling flaky tests
Ultimately, the best way to deal with flaky tests is to fix the underlying issues that are causing them to be flaky. However, this is not always possible, and in some cases it may be more practical to simply ignore or disable the tests.
How do you test for flaky tests?
Flaky tests are tests that intermittently fail without any changes to the code or tests. There are many possible causes of flaky tests, but the most common cause is race conditions.
To test for flaky tests, you need to first identify which tests are flaky. This can be done by looking at the test results over time to see if any tests intermittently fail. Once you have identified the flaky tests, you need to investigate the cause of the flakiness.
The most common cause of flaky tests is race conditions. Race conditions can occur when two or more threads are accessing the same data and one thread modifies the data before the other thread has a chance to read it. This can cause the test to fail intermittently because the order in which the threads execute can change from run to run.
To investigate race conditions, you need to look at the code that is being executed by the flaky tests. Look for any places where two or more threads are accessing the same data. If you find any, try to reproduce the flakiness by running the code in a debugger. This will allow you to see what is happening and why the test is failing.
Once you have identified the cause of the flakiness, you can fix it by adding synchronization to the code so that the threads will execute in the correct order.
How do you stop a flaky test?
There are a few things you can do to stop a flaky test:
1. First, try to identify the cause of the flakiness. Is it due to environmental factors such as network latency or data conditions? Or is it due to the code itself?
2. If the cause is environmental, try to stabilize the environment. For example, if the test is flaky due to network latency, try to use a more reliable network connection.
3. If the cause is due to the code, try to refactor the code to make it more robust. For example, if the code is flaky due to race conditions, try to use synchronization primitives to make the code thread-safe.
Why UI tests are flaky?
There are a few main reasons why UI tests can be flaky:
1. UI tests can be sensitive to changes in the UI itself. For example, if an element's ID changes, or if the layout of a page changes, a UI test that is looking for that element may break.
2. UI tests can also be sensitive to changes in the data that is being displayed in the UI. For example, if a UI test is looking for a specific piece of data on a page, and that data changes, the test may break.
3. UI tests can also be sensitive to changes in the environment in which they are run. For example, if a UI test is run on a different browser than it was developed for, it may break.
4. Finally, UI tests can be sensitive to changes in the code that is driving the UI. For example, if a UI test is looking for an element that is generated by a specific piece of code, and that code changes, the test may break.
What is flaky behavior?
Flaky behavior is when an application or service behaves in an unpredictable or unreliable way. This can manifest itself in a number of ways, such as random crashes, hangs, or data loss.
There are many possible causes of flaky behavior, ranging from hardware issues to software bugs. In some cases, it may be caused by a combination of factors.
Identifying and resolving flaky behavior can be a challenge, as it can be difficult to reproduce and may only happen intermittently. However, it is important to try to identify and fix any issues, as flaky behavior can be very frustrating for users and can lead to data loss or corruption.