JUnit rule to conditionally ignore test cases (see also http://www.codeaffine.com/2013/11/18/a-junit-rule-to-conditionally-ignore-tests/)

ConditionalIgnoreRule

/*******************************************************************************
 * Copyright (c) 2013,2014 Rüdiger Herrmann
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   Rüdiger Herrmann - initial API and implementation
 *   Matt Morrissette - allow to use non-static inner IgnoreConditions
 ******************************************************************************/
package com.codeaffine.test;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Modifier;

import org.junit.Assume;
import org.junit.rules.MethodRule;
import org.junit.runners.model.FrameworkMethod;
import org.junit.runners.model.Statement;

public class ConditionalIgnoreRule implements MethodRule {

  public interface IgnoreCondition {
    boolean isSatisfied();
  }

  @Retention(RetentionPolicy.RUNTIME)
  @Target({ElementType.METHOD})
  public @interface ConditionalIgnore {
    Class<? extends IgnoreCondition> condition();
  }

  @Override
  public Statement apply( Statement base, FrameworkMethod method, Object target ) {
    Statement result = base;
    if( hasConditionalIgnoreAnnotation( method ) ) {
      IgnoreCondition condition = getIgnoreContition( target, method );
      if( condition.isSatisfied() ) {
        result = new IgnoreStatement( condition );
      }
    }
    return result;
  }

  private static boolean hasConditionalIgnoreAnnotation( FrameworkMethod method ) {
    return method.getAnnotation( ConditionalIgnore.class ) != null;
  }

  private static IgnoreCondition getIgnoreContition( Object target, FrameworkMethod method ) {
    ConditionalIgnore annotation = method.getAnnotation( ConditionalIgnore.class );
    return new IgnoreConditionCreator( target, annotation ).create();
  }

  private static class IgnoreConditionCreator {
    private final Object target;
    private final Class<? extends IgnoreCondition> conditionType;

    IgnoreConditionCreator( Object target, ConditionalIgnore annotation ) {
      this.target = target;
      this.conditionType = annotation.condition();
    }

    IgnoreCondition create() {
      checkConditionType();
      try {
        return createCondition();
      } catch( RuntimeException re ) {
        throw re;
      } catch( Exception e ) {
        throw new RuntimeException( e );
      }
    }

    private IgnoreCondition createCondition() throws Exception {
      IgnoreCondition result;
      if( isConditionTypeStandalone() ) {
        result = conditionType.newInstance();
      } else {
        result = conditionType.getDeclaredConstructor( target.getClass() ).newInstance( target );
      }
      return result;
    }

    private void checkConditionType() {
      if( !isConditionTypeStandalone() && !isConditionTypeDeclaredInTarget() ) {
        String msg
          = "Conditional class '%s' is a member class "
          + "but was not declared inside the test case using it.\n"
          + "Either make this class a static class, "
          + "standalone class (by declaring it in it's own file) "
          + "or move it inside the test case using it";
        throw new IllegalArgumentException( String.format ( msg, conditionType.getName() ) );
      }
    }

    private boolean isConditionTypeStandalone() {
      return !conditionType.isMemberClass() || Modifier.isStatic( conditionType.getModifiers() );
    }

    private boolean isConditionTypeDeclaredInTarget() {
      return target.getClass().isAssignableFrom( conditionType.getDeclaringClass() );
    }
  }

  private static class IgnoreStatement extends Statement {
    private final IgnoreCondition condition;

    IgnoreStatement( IgnoreCondition condition ) {
      this.condition = condition;
    }

    @Override
    public void evaluate() {
      Assume.assumeTrue( "Ignored by " + condition.getClass().getSimpleName(), false );
    }
  }

}