Test-driven development: JUnit

gradle:

apply plugin: 'java'

dependencies {
  testCompile 'junit:junit:4.12'
}

apply plugin: 'java'

dependencies {

testCompile 'junit:junit:4.12'

}

maven:

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
</dependency>

<groupId>junit</groupId>

<artifactId>junit</artifactId>

</dependency>

Expected Exceptions Test

    @Test(expected = UnsupportedOperationException.class)
    public void reverseList() {
        list.getReverseList();
    }

@Test(expected = UnsupportedOperationException.class)

public void reverseList() {

list.getReverseList();

}

@RunWith

BlockJUnit4ClassRunner – default junit runner
SpringJUnit4ClassRunner allows you to use dependency injection in test classes or to create transactional test methods.
MockitoJUnitRunner for automatic mock initialization.
Suite
Parameterized

Parameters class

@RunWith(value = Parameterized.class)
public class ParametersTest {
    // ...
      @Parameters
      public static Collection<Object[]> data() {

      @Test //will be run Collection.size times
      public void testData(){
}

@RunWith(value = Parameterized.class)

public class ParametersTest {

// ...

@Parameters

public static Collection<Object[]> data() {

@Test //will be run Collection.size times

public void testData(){

}

JUnit 5 – @ExtendWith

@RunWith(SpringJUnit4ClassRunner.class)

1	@RunWith(SpringJUnit4ClassRunner.class)

replace with

@ExtendWith(SpringExtension.class)

1	@ExtendWith(SpringExtension.class)

@Rule

@Rule public ExpectedException exception = ExpectedException.none();

1	@Rule public ExpectedException exception = ExpectedException.none();

@Rule public TemporaryFolder folder = new TemporaryFolder();

1	@Rule public TemporaryFolder folder = new TemporaryFolder();

or your custom rule:

public class MyCustomRule implements TestRule {

1	public class MyCustomRule implements TestRule {

hamcrest – how to test lists

<dependency>
    <groupId>org.hamcrest</groupId>
    <artifactId>hamcrest-all</artifactId>
    <version>1.3</version>
</dependency>

<groupId>org.hamcrest</groupId>

<artifactId>hamcrest-all</artifactId>

</dependency>

// https://mvnrepository.com/artifact/org.hamcrest/java-hamcrest
testCompile group: 'org.hamcrest', name: 'java-hamcrest', version: '2.0.0.0'

1 2	// https://mvnrepository.com/artifact/org.hamcrest/java-hamcrest testCompile group: 'org.hamcrest', name: 'java-hamcrest', version: '2.0.0.0'

check if single element is in a collection

assertThat(Lists.newArrayList("a", "b", "c"), hasItem("c"));
assertThat(Lists.newArrayList("a", "b", "c"), not(hasItem("d")));

1 2	assertThat(Lists.newArrayList("a", "b", "c"), hasItem("c")); assertThat(Lists.newArrayList("a", "b", "c"), not(hasItem("d")));

check if multiple elements are in a collection

assertThat(Lists.newArrayList("a", "b", "c"), hasItems("c", "d"));

1	assertThat(Lists.newArrayList("a", "b", "c"), hasItems("c", "d"));

check all elements in a collection with strict order

assertThat(collection, contains("a", "b", "c"));

1	assertThat(collection, contains("a", "b", "c"));

check all elements in a collection with any order

assertThat(collection, containsInAnyOrder("a", "b", "c"));

1	assertThat(collection, containsInAnyOrder("a", "b", "c"));

check if collection is empty

assertThat(Lists.newArrayList(), empty());

1	assertThat(Lists.newArrayList(), empty());

check if array is empty

assertThat(new String[] {"a"}, not(emptyArray()));

1	assertThat(new String[] {"a"}, not(emptyArray()));

check if Map is empty

assertThat(Maps.newHashMap(), equalTo(Collections.EMPTY_MAP));

1	assertThat(Maps.newHashMap(), equalTo(Collections.EMPTY_MAP));

check if Iterable is empty

assertThat(Lists.newArrayList(), emptyIterable());

1	assertThat(Lists.newArrayList(), emptyIterable());

check size of a collection

assertThat(Lists.newArrayList("a", "b", "c"), hasSize(3));

1	assertThat(Lists.newArrayList("a", "b", "c"), hasSize(3));

checking size of an iterable

assertThat(Lists.newArrayList("a", "b", "c"), Matchers.<String> iterableWithSize(3));

1	assertThat(Lists.newArrayList("a", "b", "c"), Matchers.<String> iterableWithSize(3));

check condition on every item

assertThat(Lists.newArrayList(15, 20, 25, 30), everyItem(greaterThan(10)));

1	assertThat(Lists.newArrayList(15, 20, 25, 30), everyItem(greaterThan(10)));