private static Path resourceDirectoryPath(String resourceDir) throws IOException {
        URL resource = Thread.currentThread()
            .getContextClassLoader()
            .getResource(resourceDir);
        if (resource == null) {
            throw new IOException("Could not find test plugin resource: " + resourceDir);
        }
        Path file = Paths.get(resource.getFile());
        if (!Files.isDirectory(file)) {
            throw new IOException("Resource is not a directory: " + resourceDir);
        }
        if (!Files.isReadable(file)) {
            throw new IOException("Resource directory is not readable: " + resourceDir);
        }
        return file;
    }
Get all plugin classes which are included in the specified plugins
@param plugins One or more plugins which are included in the plugin path.
@return A list of plugin class names
@throws AssertionError if any plugin failed to load, or no plugins were loaded.
connect/runtime/src/test/java/org/apache/kafka/connect/runtime/isolation/TestPlugins.java