assert throws exception java code example

Example 1: 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 2: java throws exception on method

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