@Override
    public void setFirstLastFullNames(final String firstName, final String lastName) {
        Preconditions.checkArgument(StringUtils.isNotBlank(firstName), "A firstName value is required.");
        Preconditions.checkArgument(StringUtils.isNotBlank(lastName), "A lastName value is required.");
        fields.put(FIRST_NAME, firstName);
        fields.put(LAST_NAME, lastName);
        fields.put(FULL_NAME, String.format(Locale.ENGLISH, FULL_NAME_FORMAT, firstName, lastName));
    }
@Test
    public void testFirstLastRequired() {
        user = createUserImpl(null, null, null);
        assertThatThrownBy(() -> user.setFirstLastFullNames(null, "Last"))
                .isExactlyInstanceOf(IllegalArgumentException.class)
                .hasMessageContaining("A firstName value is required");

        assertThatThrownBy(() -> user.setFirstLastFullNames("First", null))
                .isExactlyInstanceOf(IllegalArgumentException.class)
                .hasMessageContaining("A lastName value is required");
    }