java assert throws exception code example

Example 1: junit 5 expected exception

@Test
void testExpectedException() {
 
  Assertions.assertThrows(NumberFormatException.class, () -> {
    Integer.parseInt("One");
  });
 
}

Example 2: junit 5 assert exception message

Throwable exceptionThatWasThrown = assertThrows(NullPointerException.class, () -> {
    codeThatThrows;
});

assertThat(exceptionThatWasThrown.getMessage(), equalTo("Message I expected to be thrown"));

Example 3: how to assert that an exception is thrown java

@Test
public void whenExceptionThrown_thenAssertionSucceeds() {
    Exception exception = assertThrows(NumberFormatException.class, () -> {
        Integer.parseInt("1a");
    });

    String expectedMessage = "For input string";
    String actualMessage = exception.getMessage();

    assertTrue(actualMessage.contains(expectedMessage));
}

Example 4: java throws exception on method

static void testMethod() throws Exception {
    String test = null;
    test.toString();
}

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