@Test
public void shouldCheckIfMandatoryFieldsAreFilled() {

    assertThat(signupActivity.isValid(), equalTo(false));
    assertEquals(userName.getError(), signupActivity.getString(R.string.username_required));
    assertEquals(password.getError(), signupActivity.getString(R.string.password_required));
    assertEquals(organisation.getError(), signupActivity.getString(R.string.organisation_required));
    assertEquals(confirmPassword.getError(), signupActivity.getString(R.string.confirm_password_required));
}