def "visits message when unavailable"() {
        def visitor = Mock(DiagnosticsVisitor)

        given:
        def availability = new ToolChainAvailability()
        availability.unavailable("some reason")

        when:
        availability.explain(visitor)

        then:
        1 * visitor.node("some reason")
    }

    def "visits message when unsupported"() {

        when:
        e.accept(visitor)

        then:
        1 * visitor.visitCause(cause)
        1 * visitor.endVisiting()

        3 * visitor.startChildren()
        1 * visitor.node(childCause1)
        1 * visitor.node(childCause4)
        1 * visitor.node(childCause3)
        1 * visitor.node(childCause2)
        3 * visitor.endChildren()
        0 * visitor._

        and:

     * FileVisitDetails}
     *
     * @param visitor The visitor.
     * @return this
     */
    FileTree visit(@DelegatesTo(FileVisitDetails.class) Closure visitor);

    /**
     * Visits the files and directories in this file tree. Files are visited in depth-first prefix order, so that a directory

        lexer.visit(visitor)

        then:
        1 * visitor.onStartJavadocTag('tag')
        1 * visitor.onText('some value')
        1 * visitor.onEndJavadocTag('tag')
        1 * visitor.onEnd()
        0 * visitor._
    }

    def javadocTagCanBeEmpty() {
        when:
        lexer.pushText("{@empty}")
        lexer.visit(visitor)

        then:
        1 * visitor.onStartJavadocTag('empty')

        1 * visitor.visitDir(included)
        0 * _
    }

    def "ignores file that is not included"() {
        def spec = Mock(Spec)
        def included = Stub(FileVisitDetails)
        def excluded = Stub(FileVisitDetails)
        def visitor = Mock(FileVisitor)

        when:
        tree.visit(visitor)

        then:
        _ * patterns.asSpec >> spec
        1 * spec.isSatisfiedBy(included) >> true

    def "walking type hierarchy happens breadth-first"() {
        def visitor = Mock(Types.TypeVisitor)
        when:
        Types.walkTypeHierarchy(Child, [Object, GroovyObject], visitor)

        then: 1 * visitor.visitType(Child) >> Types.TypeVisitResult.CONTINUE
        then: 1 * visitor.visitType(Base) >> Types.TypeVisitResult.CONTINUE
        then: 1 * visitor.visitType(Serializable) >> Types.TypeVisitResult.CONTINUE

        1 * visitor.visitInputFileProperty('inputFile', _, _, _, _, _, _, InputFilePropertyType.FILE)
        1 * visitor.visitInputFileProperty('inputFiles', _, _, _, _, _, _, InputFilePropertyType.FILES)
        1 * visitor.visitInputProperty('bean', { it.call().implementationClassIdentifier == NestedBean.name }, false)
        1 * visitor.visitInputProperty('bean.nestedInput', { it.call() == 'nested' }, false)

            private final ArtifactVisitor visitor;
            private final List<ResolvedArtifactSet.Artifacts> results = new ArrayList<>();
            private BuildOperationQueue<RunnableBuildOperation> queue;

            StartVisitAction(ArtifactVisitor visitor) {
                this.visitor = visitor;
            }

            @Override

    }

    @Override
    public void visitStructure(MinimalFileTreeStructureVisitor visitor, FileTreeInternal owner) {
        visitor.visitFileTree(dir, patternSet, owner);
    }

    @Override
    public void visit(FileVisitor visitor) {
        visitFrom(visitor, dir, RelativePath.EMPTY_ROOT, new AtomicBoolean());
    }

    /**

    }

    /**
     * Visits the external artifacts of this set.
     */
    void visitExternalArtifacts(Action<ResolvableArtifact> visitor);

    ResolvedArtifactSet EMPTY = new ResolvedArtifactSet() {
        @Override
        public void visit(Visitor visitor) {
        }

        @Override
        public void visitTransformSources(TransformSourceVisitor visitor) {
        }

        @Override