void removeFactMapping(FactMapping toRemove) {
        factMappings.remove(toRemove);
    }
@Test
    public void removeFactMapping() {
        FactMapping retrieved = modelDescriptor.addFactMapping(factIdentifier, expressionIdentifier);
        
        modelDescriptor.removeFactMapping(retrieved);
        
        assertThat(modelDescriptor.getUnmodifiableFactMappings()).doesNotContain(retrieved);
    }