and: "some variants in the component, or none"
        (0..<ownVariants).forEach {
            metadata.addVariant("variant$it", ImmutableAttributes.EMPTY)
        }

        and: "a rule that adds a variant to all components"
        metadataRuleContainer.addClassRule(
            new SpecConfigurableRule(

        }
        assert values.formatVersion == '1.1'
        assert values.createdBy.gradle.version == GradleVersion.current().version
        variants = (values.variants ?: []).collect { new Variant(it.name, it) }
    }

    @Nullable
    CreatedBy getCreatedBy() {
        def createdBy = values.createdBy
        if (createdBy == null) {
            return null
        }

This is typical of libraries published to external repositories.
In this case, we know that even if we don't have an exact match (API), we can still compile against the runtime variant (it contains _more_ than what we need to compile but it's still ok to use).

====

The rule creates an `apiElements` variant based on the `compile` configuration and a `runtimeElements` variant based on the `default` configuration of each ivy module.
For each variant, it sets the corresponding <<#sec:variant-aware-matching,Java ecosystem attributes>>.
Dependencies and artifacts of the variants are taken from the underlying configurations.

        given:
        def variantSet = variantSetOf([variant, otherVariant])
        def selector = new AttributeMatchingArtifactVariantSelector(consumerProvidedVariantFinder, attributesSchema, attributesFactory, transformedVariantFactory, dependenciesResolverFactory, failureProcessor)

        when:
        def result = selector.select(variantSet, requestedAttributes, false, factory)

        then:

                return ResolvedArtifactSet.EMPTY;
            }

            ResolvedVariantSet variantSet = new DefaultResolvedVariantSet(componentId, producerSchema, overriddenAttributes, variants);
            return variantSelector.select(variantSet, spec.getRequestAttributes(), spec.getAllowNoMatchingVariants(), this::asTransformed);
        }
    }