public FactMapping addFactMapping(int index, FactMapping toClone) {
        FactMapping toReturn = toClone.cloneFactMapping();
        factMappings.add(index, toReturn);
        return toReturn;
    }
@Test
    public void addFactMappingByIndexAndFactIdentifierAndExpressionIdentifierFail() {
        assertThatIllegalArgumentException().isThrownBy(() -> modelDescriptor.addFactMapping(1, factIdentifier, expressionIdentifier));
    }