Unravel › Java concepts › Testing

At a glance

1. 1Mapping to JUnit 5: @Before is @BeforeEach, @After is @AfterEach, @BeforeClass is @BeforeAll, @Ignore is @Disabled, @RunWith(X.class) and @Rule become @ExtendWith
2. 2@Test(expected = IllegalArgumentException.class) checks an exception (JUnit 5: assertThrows)@Test(timeout = 1000) fails slow tests.
3. 3Assert.assertEquals(expected, actual) puts the expected value firstHamcrest: assertThat(list, hasItem("a")), is(...), containsString(...).
4. 4@RunWith(MockitoJUnitRunner.class) initialises @Mock fields; @Parameterized.Parameters runs a test over a table

• JUnit 4 and 5 can run together through the Vintage engine, so a project can migrate step by step
• A very common reason for a test that "does not run" is the wrong import for @Test in a Spring Boot project that now defaults to JUnit 5
• JUnit 4 uses a Runner that finds @Test methods by reflection and runs them with @Rule interceptors; JUnit 5 splits this into the Platform (launching) and engines

import org.junit.*;import static org.junit.Assert.*;public class StackTest {  private java.util.ArrayDeque<Integer> stack;  @Before public void setUp() { stack = new java.util.ArrayDeque<>(); }  @After public void tearDown() { stack.clear(); }  @Test public void pushAndPop() { stack.push(1); assertEquals(Integer.valueOf(1), stack.pop()); }  @Test(expected = java.util.NoSuchElementException.class) public void emptyPop() { stack.pop(); }  @Ignore("not ready") @Test public void later() {}}

1. line 2 uses Assert, the core of JUnit 4 and Hamcrest
2. line 5 uses Before, the core of JUnit 4 and Hamcrest
3. line 6 uses After, the core of JUnit 4 and Hamcrest
4. line 9 uses Ignore, the core of JUnit 4 and Hamcrest

How Unravel recognises it

When you paste code, Unravel looks for these signs of junit 4 and hamcrest. Spotting them yourself is a good habit when you read unfamiliar code:

• Annotations: @RunWith @Rule @ClassRule @Before @After @BeforeClass @AfterClass @Ignore
• Types: Assert Matchers CoreMatchers TemporaryFolder ExpectedException Parameterized MockitoJUnitRunner

Part of a learning path

• Errors, logging and tests in depth · previous: Mockito: matchers, verification, spies

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