How to change tests execution order in JUnit5?

Edit: JUnit 5.4 is officially released now, so no need to use snapshots anymore.

This is now possible with JUnit 5.4.

https://junit.org/junit5/docs/current/user-guide/#writing-tests-test-execution-order

To control the order in which test methods are executed, annotate your test class or test interface with @TestMethodOrder and specify the desired MethodOrderer implementation. You can implement your own custom MethodOrderer or use one of the following built-in MethodOrderer implementations.

Alphanumeric: sorts test methods alphanumerically based on their names and formal parameter lists.

OrderAnnotation: sorts test methods numerically based on values specified via the @Order annotation.

No, not yet. For unit tests, execution order should be irrelevant. For more complex tests, JUnit is aiming to provide explicit support - test ordering would be part of that.

With version 5.8.0 onwards, test classes can be ordered too.

src/test/resources/junit-platform.properties:

# ClassOrderer$OrderAnnotation sorts classes based on their @Order annotation
junit.jupiter.testclass.order.default=org.junit.jupiter.api.ClassOrderer$OrderAnnotation

Other Junit built-in class orderer implementations:

org.junit.jupiter.api.ClassOrderer$ClassName
org.junit.jupiter.api.ClassOrderer$DisplayName
org.junit.jupiter.api.ClassOrderer$Random

For other ways (beside junit-platform.properties file) to set configuration parameters refer here.

You can also provide your own orderer. It must implement ClassOrderer interface:

package foo;
public class MyOrderer implements ClassOrderer {
    @Override
    public void orderClasses(ClassOrdererContext context) {
        Collections.shuffle(context.getClassDescriptors());
    }
}

junit.jupiter.testclass.order.default=foo.MyOrderer

Note that @Nested test classes cannot be ordered by a ClassOrderer.

Refer to JUnit 5 documentations and ClassOrderer api docs to learn more about ordering test classes.

The answer to this question is sub.version dependent. In my environment, junit-jupiter-5.5.2, the implementation of ASCII test ordering that works for me is:

import org.junit.jupiter.api.TestMethodOrder;
import org.junit.jupiter.api.MethodOrderer.Alphanumeric;

@TestMethodOrder(Alphanumeric.class)

Related orderings (e.g. explicit numbering) are documented in the JUnit 5.5.2 API.

As of JUnit 5.7, I believe the amended declarations are:

import org.junit.jupiter.api.TestMethodOrder;
import org.junit.jupiter.api.MethodOrderer.MethodName;

@TestMethodOrder(MethodName.class)

If somebody with Junit 5.7 or later wants to test this, confirmation or correction would be welcome.