JUnit 4 Exercise Solutions

Solution1.java

// Solution to 1
import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class AdditionTest {

    @Test
    public void testSum() {
        int sum = 3 + 4;
        int expectedSum = 7;
        assertEquals(expectedSum, sum);
    }
}

Solution2.java

import org.junit.Before;
import org.junit.After;
import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class CalculatorTest {

    private Calculator calculator;

    @Before
    public void setUp() {
        calculator = new Calculator();
    }

    @Test
    public void testAddition() {
        int result = calculator.add(3, 4);
        assertEquals(7, result);
    }

    @Test
    public void testSubtraction() {
        int result = calculator.subtract(5, 2);
        assertEquals(3, result);
    }

    @After
    public void tearDown() {
        calculator = null;
    }

    // Calculator class for illustration purposes
    class Calculator {
        int add(int a, int b) {
            return a + b;
        }

        int subtract(int a, int b) {
            return a - b;
        }
    }
}

Solution3.java

import org.junit.Test;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.assertFalse;

public class StringTest {

    @Test
    public void testContainsSubstring() {
        String mainString = "Hello, World!";
        String substring1 = "World";
        String substring2 = "Java";

        assertTrue(mainString.contains(substring1));
        assertFalse(mainString.contains(substring2));
    }
}

Solution4.java

import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;

public class ArrayEqualityTest {

    @Test
    public void testArrayEquality() {
        int[] array1 = {1, 2, 3, 4, 5};
        int[] array2 = {1, 2, 3, 4, 5};
        assertArrayEquals(array1, array2);
    }
}

Solution5.java

import org.junit.Test;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertNotNull;

public class ObjectNullityTest {

    @Test
    public void testObjectIsNull() {
        String nullString = null;
        assertNull(nullString);
    }

    @Test
    public void testObjectIsNotNull() {
        String nonNullString = "JUnit 4";
        assertNotNull(nonNullString);
    }
}

Solution6.java

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class FloatingPointTest {

    @Test
    public void testFloatingPointEquality() {
        double number1 = 1.3333333;
        double number2 = 4.0 / 3.0;
        double delta = 0.000001;
        assertEquals(number1, number2, delta);
    }
}

Solution7.java

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class ExceptionHandlingTest {

    @Test(expected = ArithmeticException.class)
    public void testDivisionByZero() {
        int result = 5 / 0;
    }
}

Solution8.java

import org.junit.Test;
import java.util.List;
import java.util.Arrays;
import static org.hamcrest.CoreMatchers.hasItem;
import static org.junit.Assert.assertThat;

public class CollectionTest {

    @Test
    public void testListContainsElement() {
        List<String> colors = Arrays.asList("red", "green", "blue");
        assertThat(colors, hasItem("green"));
    }
}