return Mock(ResolvedVariantSet) {
            asDescribable() >> Describables.of("mock producer")
            getVariants() >> variants
            getOverriddenAttributes() >> ImmutableAttributes.EMPTY
        }
    }

    private List<TransformedVariant> transformedVariants(List<ResolvedVariant> variants) {
        variants.collect {

 */

package org.gradle.api.internal.artifacts;

import org.gradle.api.artifacts.component.ComponentIdentifier;

/**
 * A node identifier that uniquely identifies a variant within a component by the variant's name.
 *
 * Note: Generally, variants should be identified by their attributes and capabilities, as the name
 * is more of a human-readable identifier.
 */
public class ComponentVariantNodeIdentifier implements NodeIdentifier {

           - Variant org.example:nyvu:1.0 variant greenElementsCapability2 has attributes {color=green}

   > Could not resolve project :.
     Required by:
         project :
      > Multiple incompatible variants of org.example:pi2e5:1.0 were selected:
           - Variant org.example:pi2e5:1.0 variant blueElementsCapability1 has attributes {color=blue}

        conf2.artifacts.add(Mock(PublishArtifact))
        ConfigurationVariant variant2 = conf2.outgoing.getVariants().create("variant2")
        variant2.attributes.attribute(Attribute.of("foo2", String), "bar2")
        variant2.artifacts.add(Stub(PublishArtifact))
        variant2.artifacts.add(Stub(PublishArtifact))

        when:

            baseVariant = immutableMetadata.getConfiguration('runtime')
        }

        then:
        variants.size() == initialVariantCount + 1
        variants.last().name == 'new-variant'
        variants.last().attributes == baseVariant.attributes
        variants.last().capabilities == baseVariant.capabilities

            Collections.emptyList()
        );

        // It is fine if no graph variants satisfy our request.
        // Variant reselection allows no target variants to be found.
        if (graphVariant == null) {
            return ImmutableSet.of();
        }

        // Next, return all artifact variants for the selected graph variant.
        return getArtifactsForGraphVariant(graphVariant);
    }

    /**

        if (variants == null || variants.isEmpty() || !allArtifactSet.isEmpty()) {
            visitor.visitOwnVariant(displayName, attributes.asImmutable(), allArtifactSet);
        }
        if (variants != null) {
            for (ConfigurationVariantInternal variant : variants.withType(ConfigurationVariantInternal.class)) {

        def variantDef = publications.variants.create("child")
        variantDef.attributes.attribute(Attribute.of("thing", String), "value")
        variantDef.artifacts.add(artifact)

        expect:
        def variants = getOutgoingVariants(publications)
        variants.size() == 1

        def child = variants.first()
        child.displayName.displayName == '<config> variant child'

Secondary variants are variants created via the Configuration#getOutgoing(): ConfigurationPublications API which also participate in selection, in addition to the configuration itself.

BUILD SUCCESSFUL in 0s...

        failure.assertHasCause("""Multiple incompatible variants of org:test:1.0 were selected:
   - Variant api1 has attributes {custom=c1, org.gradle.status=${MultipleVariantSelectionIntegrationTest.defaultStatus()}}
   - Variant runtime2 has attributes {custom=c2, org.gradle.status=${MultipleVariantSelectionIntegrationTest.defaultStatus()}}""")
    }