Junit4.10 source code analysis: 5.2 Rule

Testrule declares factory methods

Testrule isFactory method modeCreator role in -- declare the factory method.

package org.junit.rules;import org.junit.runner.Description;import org.junit.runners.model.Statement;public interface TestRule {Statement apply(Statement base, Description description);}

To use rule, the test programmer must write the code:

1. mystatement -- one of statementNew decoration object. (Example of the use of JUnit rule), the status is equivalent to expectexception.

package rule;import static tool.Print.*;//pln(Object)import org.junit.runners.model.Statement;/** * * @author yqj2065 */public class MyStatement extends Statement {    private final Statement base;    public MyStatement( Statement base ) {        this.base = base;    }    @Override public void evaluate() throws Throwable {        pln( "before...sth..sth" );        try {            base.evaluate();        } finally {             pln( "after...sth..sth" );        }    }}

2. A specific factory, that is, defining the factory Method Subclass of testrule. Myrule will create a statement New decoration object mystatement. Similar to the general usage of the factory method model, the specific factory and specific products correspond one by one.

package rule;import org.junit.rules.TestRule;import org.junit.runners.model.Statement;import org.junit.runner.Description;public class MyRule implements TestRule  {    @Override    public Statement apply(Statement base, Description description) {        return new MyStatement( base );    }}

3. Use a new decoration object

The user class blockjunit4classrunner uses the built-in statement decoration objects of JUnit such as expectexception;The statement decoration object compiled by the test programmer needs to be embedded into the unit test class through @ rule..

package rule;import org.junit.Rule;import org.junit.Test;public class MyTest {       @Rule    public MyRule myRule = new MyRule();        @Test()    public void xx() {        System.out.println( "xx()..." );    }}

Run mytest in the development environment and output:
Before... ......
XX ()...
After...

Rulechain

Junit4.10 source code analysis: 5.2 Rule