Rene-Frerichs

@Test
public void assertJ() throws Exception {
  assertThatThrownBy(this::methodThrowsIllegalArgument)
    .isInstanceOf(IllegalArgumentException.class)
    .hasMessage("Invalid Argument");
}

Rene-Frerichs

@Rule
public ExpectedException thrownException = ExpectedException.none();
  
@Test
public void exceptionRule() {
  thrownException.expect(IllegalArgumentException.class);
  thrownException.expectMessage("Invalid Argument");
  methodThrowsIllegalArgument();
}

Rene-Frerichs

@Test(expected = IllegalArgumentException.class)
public void expected() {
  methodThrowsIllegalArgument();
}

Rene-Frerichs

@Test
public void tryCatch() {
  try {
    methodThrowsIllegalArgument();
    fail("Expected IllegalArgumentException!");
  } catch (IllegalArgumentException exception) {
    assertThat(exception.getMessage(), is("Invalid Argument"));
  }
}

Rene-Frerichs

import static org.assertj.core.api.Assertions.assertThatThrownBy;
import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.fail;

import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.ExpectedException;

public class ExceptionTestingTest {

Rene-Frerichs

@Test
public void fileAssertion() {
  File file = createFile("openKnowledge.txt", "offen, kundig, gut!");
  
  assertThat(file).exists().hasExtension("txt").isFile().isRelative();
  assertThat(contentOf(file)).startsWith("offen").contains("kundig").endsWith("gut!");
}

Rene-Frerichs

@Rule
public JUnitSoftAssertions softly = new JUnitSoftAssertions();

String openKnowledge = "offen, kundig, gut!";

@Test
public void exampleNormalAssertion() {
  assertThat(openKnowledge).startsWith("kundig").endsWith("offen");
  // -> java.lang.AssertionError: Expecting: <"offen, kundig, gut!"> to start with: <"kundig">
}