Notes on how to use each JUnit Rule

What is Rule

TestRule or an instance of a class that inherits TestRule By annotating @Rule and setting it in the field of the test class It is possible to add various functions to the test.

http://junit.org/junit4/javadoc/4.12/org/junit/rules/TestRule.html

Constitution

$ tree
.
├── build.gradle
└── src
    └── test
        └── java
            └── example
                ├── TestTemporaryFolder.java
                └── TestTestName.java
$ cat build.gradle
apply plugin: "java"

repositories {
  mavenCentral()
}

dependencies {
  testCompile "junit:junit:4.+"
}

test {
  testLogging.showStandardStreams = true
}

TestName

http://junit.org/junit4/javadoc/4.12/org/junit/rules/TestName.html

TestTestName.java

package example;

import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.TestName;
import org.junit.runner.Description;

import static org.junit.Assert.assertEquals;

public class TestTestName
{
    @Rule
    public TestName testName = new TestName()
    {
        @Override
        public void starting(Description d)
        {
            System.out.println(
                String.format("%s starting ...", d.getMethodName()));
            super.starting(d);
        }
    };

    @Test
    public void testMethodA()
    {
        System.out.println(
            String.format("%s running ...", testName.getMethodName()));
        assertEquals("testMethodA", testName.getMethodName());
    }

    @Test
    public void testMethodB()
    {
        System.out.println(
            String.format("%s running ...", testName.getMethodName()));
        assertEquals("testMethodB", testName.getMethodName());
    }
}

$ gradle -Dtest.single=TestTestName test

> Task :test

example.TestTestName > testMethodA STANDARD_OUT
    testMethodA starting ...
    testMethodA running ...

example.TestTestName > testMethodB STANDARD_OUT
    testMethodB starting ...
    testMethodB running ...


BUILD SUCCESSFUL in 1s
2 actionable tasks: 1 executed, 1 up-to-date

TemporaryFolder

http://junit.org/junit4/javadoc/4.12/org/junit/rules/TemporaryFolder.html

TestTemporaryFolder.java

package example;

import java.io.File;
import java.io.IOException;
import org.junit.After;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.TemporaryFolder;

import static org.junit.Assert.assertTrue;

public class TestTemporaryFolder
{
    File tempFile = null;

    @Rule
    public TemporaryFolder tempFolder = new TemporaryFolder()
    {
        @Override
        protected void before() throws Throwable
        {
            System.out.println("TemporaryFolder.before running ...");
            super.before();
        }

        @Override
        protected void after()
        {
            System.out.println("TemporaryFolder.after running ...");
            super.delete();
        }
    };

    @Before
    public void before() throws IOException
    {
        System.out.println("TestTemporaryFolder.before running ...");
        tempFile = tempFolder.newFile();
    }

    @After
    public void after()
    {
        System.out.println("TestTemporaryFolder.after running ...");
    }

    @Test
    public void testMethodA()
    {
        System.out.println("testMethodA running ...");
        System.out.println(String.format("tempFile name: %s", tempFile.getName()));
        assertTrue(tempFile.exists());
    }

    @Test
    public void testMethodB()
    {
        System.out.println("testMethodA running ...");
        System.out.println(String.format("tempFile name: %s", tempFile.getName()));
        assertTrue(tempFile.exists());
    }
}

$ gradle -Dtest.single=TestTemporaryFolder test

> Task :test

example.TestTemporaryFolder > testMethodA STANDARD_OUT
    TemporaryFolder.before running ...
    TestTemporaryFolder.before running ...
    testMethodA running ...
    tempFile name: junit2803814005363359855.tmp
    TestTemporaryFolder.after running ...
    TemporaryFolder.after running ...

example.TestTemporaryFolder > testMethodB STANDARD_OUT
    TemporaryFolder.before running ...
    TestTemporaryFolder.before running ...
    testMethodA running ...
    tempFile name: junit23544542917867853.tmp
    TestTemporaryFolder.after running ...
    TemporaryFolder.after running ...


BUILD SUCCESSFUL in 2s
2 actionable tasks: 1 executed, 1 up-to-date