package ru.job4j;

import org.junit.Test;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import static org.hamcrest.core.Is.is;
import static org.junit.Assert.assertThat;

/**
* Test.
* 
* @author Kucyh Vasily
* @version $Id$
* @since 0.1
*/
public class CalculateTest {

	/**
	* Test add.
	*/
	@Test
	public void whenAddOneToOneThenTwo() {

		ByteArrayOutputStream out = new ByteArrayOutputStream();
		
		System.setOut(new PrintStream(out));

		Calculate.main(null);

		assertThat(
			out.toString(), 
			is(
				String.format("Hello world%s", 
				System.getProperty("line.separator")
				)
			)
		);

	}

}

package ru.job4j;

import org.junit.Test;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import static org.hamcrest.core.Is.is;
import static org.junit.Assert.assertThat;

/**
* Test.
*
* @author Kucyh Vasily (mailto:basil135@mail.ru)
* @version $Id$
* @since 0.1
*/
public class CalculateTest {

	/**
	* Test add.
	*/
	@Test
	public void whenAddOneToOneThenTwo() {

		ByteArrayOutputStream out = new ByteArrayOutputStream();

		System.setOut(new PrintStream(out));

		Calculate.main(null);

		assertThat(
			out.toString(),
			is(
				String.format("Hello world%s",
				System.getProperty("line.separator")
				)
			)
		);

	}

}

Refactor CalculateTest.java