### Question:
IsNumber implements Validation { @Override public String getErrorMessage(final Context context) { return context.getString(R.string.formvalidations_numeric); } private  IsNumber(); static IsNumber build(); @Override String getErrorMessage(final Context context); @Override boolean isValid(final String value);  }### Answer:
@Test public void testGetErrorMessage() throws Exception { final String errorMessage = mIsNumber.getErrorMessage(mActivity); assertNotNull(errorMessage); }