How do I define an order to run junit tests in Intellij?

Question

I have a flaky junit test that only fails if I run all my tests. I think that one test is causing another test to fail, I want to prove it before I try to fix it.

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Answer 1

According to JUnit's wiki:

By design, JUnit does not specify the execution order of test method invocations. Until now, the methods were simply invoked in the order returned by the reflection API. However, using the JVM order is unwise since the Java platform does not specify any particular order, and in fact JDK 7 returns a more or less random order. Of course, well-written test code would not assume any order, but some do, and a predictable failure is better than a random failure on certain platforms.

From version 4.11, JUnit will by default use a deterministic, but not predictable, order (MethodSorters.DEFAULT). To change the test execution order simply annotate your test class using @FixMethodOrder and specify one of the available MethodSorters:

@FixMethodOrder(MethodSorters.JVM): Leaves the test methods in the order returned by the JVM. This order may vary from run to run.

@FixMethodOrder(MethodSorters.NAME_ASCENDING): Sorts the test methods by method name, in lexicographic order.

You could use MethodSorters.NAME_ASCENDING and change your method names to match with your specific order. I know you're using this just for debugging sake but it's a Test Smell to rely on your test methods execution order and JUnit does not provide more finer grain control over test methods execution order