public FactMapping addFactMapping(int index, FactMapping toClone) {
        FactMapping toReturn = toClone.cloneFactMapping();
        factMappings.add(index, toReturn);
        return toReturn;
    }
@Test
    public void addFactMapping_byIndexAndFactMapping() {
        FactMapping toClone = new FactMapping();
        toClone.setFactAlias("ALIAS");
        toClone.setExpressionAlias("EXPRESSION_ALIAS");
        
        final FactMapping cloned = modelDescriptor.addFactMapping(0, toClone);
        
        assertThat(cloned.getFactAlias()).isEqualTo(toClone.getFactAlias());
        assertThat(cloned.getExpressionAlias()).isEqualTo(toClone.getExpressionAlias());
    }