In the real world, extensions typically implement several of the previously explained extension points. For example, SpringExtension (explained in detail in chapter 5, Integration of JUnit 5 with external frameworks) implements the extensions points BeforeAllCallback, TestInstancePostProcessor, ParameterResolver, among others. The following snippet provides the structure of SpringExtension:

package org.springframework.test.context.junit.jupiter;

import org.junit.jupiter.api.extension.*;

public class SpringExtension implements BeforeAllCallback,     
   AfterAllCallback,
   TestInstancePostProcessor, BeforeEachCallback, AfterEachCallback,
   BeforeTestExecutionCallback, AfterTestExecutionCallback,
   ParameterResolver {

   @Override
   public void afterTestExecution(TestExtensionContext context) 
    throws Exception {
      // implementation
   }

   // Rest of methods
}