Example of JUnit test for CTU PJV homework assignment 01

HomeworkTestBase.java

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 */
package test;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import org.junit.After;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import static org.junit.Assert.*;
import org.junit.Before;
/**
 *
 * @author mareda
 */
public abstract class HomeworkTestBase {
    @BeforeClass
    public static void setUpClass() {
    }
    
    @AfterClass
    public static void tearDownClass() {
    }
    // <3 Thanks to http://stackoverflow.com/q/1119385/607407 
    protected final ByteArrayOutputStream outContent = new ByteArrayOutputStream();
    // sterr not used yet, but might be useful in future assignments
    protected final ByteArrayOutputStream errContent = new ByteArrayOutputStream();    

    /*
     @returns Output without \r characters which are added on Windows.
    */
    protected String sanitizedOutput() {
        return outContent.toString().replace("\r", "");
    }
    /**
     * Override this to execute homework assignment internal code (which generates std io)
     */
    protected abstract void runHW();
    
    protected void testHWBasic(String input, String expected_output) {
        simulateIn(input);
        // Homework assignment executes here
        runHW();
        assertEquals(expected_output, sanitizedOutput());
    }
    
    public static void simulateIn(final String str) {
        // Simulated STDIN
        final ByteArrayInputStream in = new ByteArrayInputStream(str.getBytes());
        System.setIn(in);
    }
    @Before
    public void setUpStreams() {
        System.setOut(new PrintStream(outContent));
        System.setErr(new PrintStream(errContent));
    }

    @After
    public void cleanUpStreams() {
        System.setOut(null);
        System.setErr(null);
        System.setIn(null);
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>cz.cvut.fel.pjv</groupId>
    <artifactId>lab01</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <dependencies>
        <!-- Important shit here: -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        
        <src.dir>src/</src.dir>
        <test.dir>test/</test.dir>
        <resource.dir>resources/</resource.dir>
    </properties>
</project>

TestCalculator.java

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 */
package test;

import org.junit.Test;
import static org.junit.Assert.*;
import cz.cvut.fel.pjv.Lab01;

/**
 *
 * @author mareda
 */
public class TestCalculator extends HomeworkTestBase {
    
    public TestCalculator() {
    }
    /**
     * Shorthand for formated number output
     * @param number 
     * @param precision Number of decimal places to show.  Trailing zeros will appear to fully fill the number of requested places
     * @return 
     */
    protected static String forNum(double number, int precision) {
        final String precisionFormula = "%."+Integer.toString(precision)+"f";
        return String.format(precisionFormula, number);
    }
    protected static String formatResult(double A, String operator, double B, double result, int precision) {
        return forNum(A,precision)+" "+operator+" "+forNum(B,precision)+" = "+forNum(result,precision)+"\n";
    }
    
    @Override
    protected void runHW() {
        new Lab01().start(new String[] {});
    }
    
    protected static final String INTRO = "Vyber operaci (1-soucet, 2-rozdil, 3-soucin, 4-podil):\n";
    
    protected static final String SCITANEC = "Zadej scitanec: \n";
    protected static final String CINITEL = "Zadej cinitel: \n"; 
    protected static final String DELENEC = "Zadej delenec: \n";
    protected static final String DELITEL = "Zadej delitel: \n";
    protected static final String MENSENEC = "Zadej scitanec: \n";
    protected static final String MENSITEL = "Zadej scitanec: \n";
    
    protected static final String SCITANI = SCITANEC+SCITANEC;
    protected static final String NASOBENI = CINITEL+CINITEL;
    protected static final String ODCITANI = MENSENEC+MENSITEL;
    protected static final String DELENI = DELENEC+DELITEL;
    
    protected static final String ERR_DIVIDE_BY_ZERO = "Pokus o deleni nulou!\n";
    protected static final String ERR_INVALID_CHOICE = "Chybna volba!\n";
    protected static final String ERR_NEGATIVE_PRECISION = "Chyba - musi byt zadane kladne cislo!\n";
    
    protected static final String PRECISION = "Zadej pocet desetinnych mist: \n";
    
    
    
    @Test
    public void TestOnePlusOne() throws Exception {
        testHWBasic("1 1 1 1", INTRO + SCITANI+ PRECISION + formatResult(1, "+", 1, 2, 1));
    }
    @Test
    public void TestDivideByZero() throws Exception {
        testHWBasic("4 1 0 1", INTRO + DELENI + ERR_DIVIDE_BY_ZERO);
    }
    @Test
    public void TestIntDivide() throws Exception {
        testHWBasic("4 1 10 0", INTRO + DELENI + PRECISION + formatResult(1, "/", 10, 0, 0));
    }
    @Test
    public void TestInvalidChoice() throws Exception {
        testHWBasic("5 1 10 0", INTRO + ERR_INVALID_CHOICE);
    }
    
    @Test
    public void TestInvalidPrecision() throws Exception {
        testHWBasic("1 1 10 -5", INTRO + SCITANI + PRECISION + ERR_NEGATIVE_PRECISION);
    }
    
    @Test
    public void TestDoubleMultiply() throws Exception {
        double A = 12.345678;
        double B = 1.23456;
        testHWBasic("3 "+String.format("%f", A)+" "+String.format("%f", B)+" 3", INTRO + NASOBENI + PRECISION + formatResult(A, "*", B, 15.241, 3));
    }
}