cpp-library-variant-task-graph.png...

  compileTestVariantCpp -> linkTestVariant -> installTestVariant -> runTestVariant [dir=back, style=dashed]
  compileTestVariantCpp[label=<compile<i>Variant</i>Cpp>]
  linkTestVariant[label=<link<i>Variant</i>>]
  installTestVariant[label=<installTest<i>Variant</i>>]
  runTestVariant[label=<runTest<i>Variant</i>>]

        then: "the result should have the variant added by the rule"
        def variantsForGraphTraversal = result.variantsForGraphTraversal
        variantsForGraphTraversal.size() == ownVariants + 1
        def variant = variantsForGraphTraversal.find { it.name == "test" }
        variant != null
        "org.gradle.test" in variant.attributes.keySet().collect { it.name }

        where:

    @Override
    public Set<? extends SoftwareComponent> getVariants() {
        return variants;
    }

    public void addArtifact(PublishArtifact artifact) {
        artifacts.add(artifact);
    }

    /**
     * Adds a child variant
     */
    public void addVariant(SoftwareComponent variant) {
        variants.add(variant);
    }

     * times with different variants (for example, the main component and its test fixtures). The dependencies
     * of each variant are different, but the {@link #getDependencies() method} doesn't give access to each
     * variant individual dependencies.
     *
     * <p>
     * The variant must be a {@linkplain #getVariants() selected variant} of this component.

    /**
     * Define a variant with attributes. Variants are only published when using {@link #withModuleMetadata()}.
     */
    MavenModule variant(String variant, Map<String, String> attributes)

    /**
     * Define a variant with attributes. Variants are only published when using {@link #withModuleMetadata()}.
     */

    private final DomainObjectSet<SoftwareComponent> variants;

    public MainExecutableVariant(ObjectFactory objectFactory) {
        variants = objectFactory.domainObjectSet(SoftwareComponent.class);
    }

    @Override
    public String getName() {
        return "main";
    }

    @Override
    public Set<SoftwareComponent> getVariants() {
        return variants;
    }

        long instanceId = decoder.readSmallLong();
        VariantGraphResolveState variant = variants.get(instanceId);
        if (variant == null) {
            throw new IllegalStateException("No variant with id " + instanceId + " found.");
        }
        return variant;
    }

import java.util.List;
import java.util.Set;

/**
 * Immutable metadata for a component variant instance that is used to perform dependency graph resolution.
 *
 * <p>Note that this metadata does not provide any information about the available artifacts of this variants, as this may be expensive to resolve.
 * Information about the artifacts can be accessed via the methods of {@link ComponentGraphResolveState}.</p>

    /**
     * Add a rule for adjusting an existing variant of the component.
     *
     * @param name name of the variant to adjust (e.g. 'compile')
     * @param action the action to modify the variant
     *
     * @since 4.4
     */
    void withVariant(String name, Action<? super VariantMetadata> action);

    /**
     * Add a rule for adjusting all variants of a component.
     *