) {
        warningLogger = watchMode.loggerForWarnings(LOGGER);
        stateInvalidatedAtStartOfBuild = false;
        reasonForNotWatchingFiles = null;
        updateRootUnderLock(currentRoot -> buildOperationRunner.call(new CallableBuildOperation<SnapshotHierarchy>() {
            @Override
            public SnapshotHierarchy call(BuildOperationContext context) {

        updateLock.lock();
        try {
            runnable.run();
        } finally {
            updateLock.unlock();
        }
    }

    protected void updateRootUnderLock(UnaryOperator<SnapshotHierarchy> updateFunction) {
        underLock(() -> {
            SnapshotHierarchy currentRoot = root;
            root = updateFunction.apply(currentRoot);
        });
    }

        when:
        watchingVirtualFileSystem.updateRootUnderLock { root -> nonEmptySnapshotHierarchy }
        watchingVirtualFileSystem.afterBuildStarted(WatchMode.DISABLED, VfsLogging.NORMAL, WatchLogging.NORMAL, buildOperationRunner)
        then:
        0 * _

        watchingVirtualFileSystem.root == emptySnapshotHierarchy

        when:
        watchingVirtualFileSystem.updateRootUnderLock { root -> nonEmptySnapshotHierarchy }

        BuildOperationRunner buildOperationRunner
    ) {
        if (watchMode == WatchMode.ENABLED) {
            LOGGER.warn("Watching the file system is not supported.");
        }
        updateRootUnderLock(vfsRoot -> buildOperationRunner.call(new CallableBuildOperation<SnapshotHierarchy>() {
            @Override
            public SnapshotHierarchy call(BuildOperationContext context) {

        then:
        watchingNotSupportedVfs.root == emptySnapshotHierarchy

        when:
        watchingNotSupportedVfs.updateRootUnderLock { root -> nonEmptySnapshotHierarchy }
        watchingNotSupportedVfs.beforeBuildFinished(watchMode, VfsLogging.NORMAL, WatchLogging.NORMAL, buildOperationRunner, Integer.MAX_VALUE)

        return updateFunction.update(SnapshotHierarchy.NodeDiffListener.NOOP);
    }

    public void setRoot(SnapshotHierarchy newRoot) {
        updateRootUnderLock(root -> newRoot);
    }

    public SnapshotHierarchy getRoot() {
        return root;
    }