package org.junit.internal.builders;

import org.junit.runner.RunWith;
import org.junit.runner.Runner;
import org.junit.runners.model.InitializationError;
import org.junit.runners.model.RunnerBuilder;

import java.lang.reflect.Modifier;


The AnnotatedBuilder is a strategy for constructing runners for test class that have been annotated with the @RunWith annotation. All tests within this class will be executed using the runner that was specified within the annotation. 

If a runner supports inner member classes, the member classes will inherit the runner from the enclosing class, e.g.:
@RunWith(MyRunner.class)
public class MyTest {
    // some tests might go here
    public class MyMemberClass {
        @Test
        public void thisTestRunsWith_MyRunner() {
            // some test logic
        }
        // some more tests might go here
    }
    @RunWith(AnotherRunner.class)
    public class AnotherMemberClass {
        // some tests might go here
        public class DeepInnerClass {
            @Test
            public void thisTestRunsWith_AnotherRunner() {
                // some test logic
            }
        }
        public class DeepInheritedClass extends SuperTest {
            @Test
            public void thisTestRunsWith_SuperRunner() {
                // some test logic
            }
        }
    }
}
@RunWith(SuperRunner.class)
public class SuperTest {
    // some tests might go here
}

The key points to note here are:

    
If there is no RunWith annotation, no runner will be created.
    
The resolve step is inside-out, e.g. the closest RunWith annotation wins
    
RunWith annotations are inherited and work as if the class was annotated itself.
    
The default JUnit runner does not support inner member classes,
        so this is only valid for custom runners that support inner member classes.
    
Custom runners with support for inner classes may or may not support RunWith annotations for member
        classes. Please refer to the custom runner documentation.

See Also:
RunnerBuilder
RunWith
Since:
4.0/**
 * The {@code AnnotatedBuilder} is a strategy for constructing runners for test class that have been annotated with the
 * {@code @RunWith} annotation. All tests within this class will be executed using the runner that was specified within
 * the annotation.
 * <p>
 * If a runner supports inner member classes, the member classes will inherit the runner from the enclosing class, e.g.:
 * <pre>
 * &#064;RunWith(MyRunner.class)
 * public class MyTest {
 *     // some tests might go here
 *
 *     public class MyMemberClass {
 *         &#064;Test
 *         public void thisTestRunsWith_MyRunner() {
 *             // some test logic
 *         }
 *
 *         // some more tests might go here
 *     }
 *
 *     &#064;RunWith(AnotherRunner.class)
 *     public class AnotherMemberClass {
 *         // some tests might go here
 *
 *         public class DeepInnerClass {
 *             &#064;Test
 *             public void thisTestRunsWith_AnotherRunner() {
 *                 // some test logic
 *             }
 *         }
 *
 *         public class DeepInheritedClass extends SuperTest {
 *             &#064;Test
 *             public void thisTestRunsWith_SuperRunner() {
 *                 // some test logic
 *             }
 *         }
 *     }
 * }
 *
 * &#064;RunWith(SuperRunner.class)
 * public class SuperTest {
 *     // some tests might go here
 * }
 * </pre>
 * The key points to note here are:
 * <ul>
 *     <li>If there is no RunWith annotation, no runner will be created.</li>
 *     <li>The resolve step is inside-out, e.g. the closest RunWith annotation wins</li>
 *     <li>RunWith annotations are inherited and work as if the class was annotated itself.</li>
 *     <li>The default JUnit runner does not support inner member classes,
 *         so this is only valid for custom runners that support inner member classes.</li>
 *     <li>Custom runners with support for inner classes may or may not support RunWith annotations for member
 *         classes. Please refer to the custom runner documentation.</li>
 * </ul>
 *
 * @see org.junit.runners.model.RunnerBuilder
 * @see org.junit.runner.RunWith
 * @since 4.0
 */
public class AnnotatedBuilder extends RunnerBuilder {
    private static final String CONSTRUCTOR_ERROR_FORMAT = "Custom runner class %s should have a public constructor with signature %s(Class testClass)";

    private final RunnerBuilder suiteBuilder;

    public AnnotatedBuilder(RunnerBuilder suiteBuilder) {
        this.suiteBuilder = suiteBuilder;
    }

    @Override
    public Runner runnerForClass(Class<?> testClass) throws Exception {
        for (Class<?> currentTestClass = testClass; currentTestClass != null;
             currentTestClass = getEnclosingClassForNonStaticMemberClass(currentTestClass)) {
            RunWith annotation = currentTestClass.getAnnotation(RunWith.class);
            if (annotation != null) {
                return buildRunner(annotation.value(), testClass);
            }
        }

        return null;
    }

    private Class<?> getEnclosingClassForNonStaticMemberClass(Class<?> currentTestClass) {
        if (currentTestClass.isMemberClass() && !Modifier.isStatic(currentTestClass.getModifiers())) {
            return currentTestClass.getEnclosingClass();
        } else {
            return null;
        }
    }

    public Runner buildRunner(Class<? extends Runner> runnerClass,
            Class<?> testClass) throws Exception {
        try {
            return runnerClass.getConstructor(Class.class).newInstance(testClass);
        } catch (NoSuchMethodException e) {
            try {
                return runnerClass.getConstructor(Class.class,
                        RunnerBuilder.class).newInstance(testClass, suiteBuilder);
            } catch (NoSuchMethodException e2) {
                String simpleName = runnerClass.getSimpleName();
                throw new InitializationError(String.format(
                        CONSTRUCTOR_ERROR_FORMAT, simpleName, simpleName));
            }
        }
    }
}