package org.junit.rules;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.junit.Rule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;
/**
* The {@code RuleChain} can be used for creating composite rules. You create a
* {@code RuleChain} with {@link #outerRule(TestRule)} and subsequent calls of
* {@link #around(TestRule)}:
*
* <pre>
* public abstract class CompositeRules {
* public static TestRule extendedLogging() {
* return RuleChain.outerRule(new LoggingRule("outer rule"))
* .around(new LoggingRule("middle rule"))
* .around(new LoggingRule("inner rule"));
* }
* }
* </pre>
*
* <pre>
* public class UseRuleChain {
* @Rule
* public final TestRule extendedLogging = CompositeRules.extendedLogging();
*
* @Test
* public void example() {
* assertTrue(true);
* }
* }
* </pre>
*
* writes the log
*
* <pre>
* starting outer rule
* starting middle rule
* starting inner rule
* finished inner rule
* finished middle rule
* finished outer rule
* </pre>
*
* In older versions of JUnit (before 4.13) {@code RuleChain} was used for
* ordering rules. We recommend to not use it for this purpose anymore. You can
* use the attribute {@code order} of the annotation {@link Rule#order() Rule}
* or {@link org.junit.ClassRule#order() ClassRule} for ordering rules.
*
* @see org.junit.Rule#order()
* @see org.junit.ClassRule#order()
* @since 4.10
*/
public class RuleChain implements TestRule {
private static final RuleChain EMPTY_CHAIN = new RuleChain(
Collections.<TestRule>emptyList());
private List<TestRule> rulesStartingWithInnerMost;
/**
* Returns a {@code RuleChain} without a {@link TestRule}. This method may
* be the starting point of a {@code RuleChain}.
*
* @return a {@code RuleChain} without a {@link TestRule}.
*/
public static RuleChain emptyRuleChain() {
return EMPTY_CHAIN;
}
/**
* Returns a {@code RuleChain} with a single {@link TestRule}. This method
* is the usual starting point of a {@code RuleChain}.
*
* @param outerRule the outer rule of the {@code RuleChain}.
* @return a {@code RuleChain} with a single {@link TestRule}.
*/
public static RuleChain outerRule(TestRule outerRule) {
return emptyRuleChain().around(outerRule);
}
private RuleChain(List<TestRule> rules) {
this.rulesStartingWithInnerMost = rules;
}
/**
* Create a new {@code RuleChain}, which encloses the given {@link TestRule} with
* the rules of the current {@code RuleChain}.
*
* @param enclosedRule the rule to enclose; must not be {@code null}.
* @return a new {@code RuleChain}.
* @throws NullPointerException if the argument {@code enclosedRule} is {@code null}
*/
public RuleChain around(TestRule enclosedRule) {
if (enclosedRule == null) {
throw new NullPointerException("The enclosed rule must not be null");
}
List<TestRule> rulesOfNewChain = new ArrayList<TestRule>();
rulesOfNewChain.add(enclosedRule);
rulesOfNewChain.addAll(rulesStartingWithInnerMost);
return new RuleChain(rulesOfNewChain);
}
/**
* {@inheritDoc}
*/
public Statement apply(Statement base, Description description) {
return new RunRules(base, rulesStartingWithInnerMost, description);
}
}