private Path storeFile(Path path, byte[] bytes) {
        path = resolvePath(path);
        if (storeMode == StoreMode.IN_MEMORY) {
            files.put(path, bytes);
        } else {
            files.put(path, new byte[0]);
        }
        return path;
    }
Creates a mock manifest that stores files in memory and uses a
base directory of "/".
smithy-build/src/main/java/software/amazon/smithy/build/MockManifest.java