Java junit 5

Documentation

official docs	https://junit.org/junit5/docs/current/user-guide/
javadocs	https://junit.org/junit5/docs/current/api/
homepage	https://junit.org/junit5/

Usage

JUnit has a standalone console runner that can be used. If you are already using a build system, I recommend using that to run your tests.

java maven plugin: junit

Configuration

stdout/stderr

By default, stdout/stderr is not printed in output. You can enable output, but unlike python it is printed for both passing/failing tests.

<plugin...>
    <configuration>
        <junit.platform.output.capture.stdout>true</junit.platform.output.capture.stdout>
        <junit.platform.output.capture.stderr>true</junit.platform.output.capture.stderr>
    </configuration>
</plugin...>

Syntax

Simple Example

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;


public class TestApp
{
    @Test
    void four_plus_four_is_eight()
    {
        int sum = 4 + 4;
        Assertions.assertEquals(sum, 8);
    }
}

I like to map out methods in nested classes.

import org.junit.jupiter.Test;
import org.junit.jupiter.Assertions;
import org.junit.jupiter.Nested;

class TestPrinter
{
    @Nested  // <-- allows nested class to be visible to junit
    class Test_print
    {
        @Test
        void test_blankpage()
        {
            Printer printer = new Printer();
            String result = printer.print();
            String expects = "";
            Assertions.assertEquals(expects, result);
        }
    }
}

Assertions

Assertions.fail("reason");

Assertions.assertEquals(x, y);
Assertions.assertSame(x, y);
Assertions.assertTrue(x, y);

Annotations

Annotations are used to indicate tests, setup/teardown methods etc.

Setup/Teardown

This list is not complete, see docs.

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.AfterEach;


class TestClass
{
    @BeforeAll
    public void setup_module() {};

    @AfterAll
    public void teardown_module() {};

    @BeforeEach
    public void setup_method() {};

    @AfterEach
    public void teardown_method() {};
}

Parametrized Tests

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;

class TestMyClass
{
    String[] alphabet = {"a", "b", "c", "d", "e", ...};

    @ParameterizedTest
    @ValueSource(strings = {"a", "b", "c"})
    void test_is_letter(String ch)
    {
        Assertions.assert(ch in alphabet);
    }
}

Troubleshooting

maven/eclipse cannot find tests

• Ensure tests are under ${project}/src/test/../Test*.java
• Ensure test-class matches filename