private static void writeAndRead(FileSystem fs, String path, String text) throws IOException {
    Path p = fs.getPath(path);
    Files.write(p, ImmutableList.of(text), UTF_8);
    List<String> lines = Files.readAllLines(p, UTF_8);
    assertEquals(text, lines.get(0));
  }
This method is really just testing that {@code Jimfs.newFileSystem()} succeeds. Without special
handling, when the system class loader loads our {@code FileSystemProvider} implementation as a
service and this code (the user code) is loaded in a separate class loader, the system-loaded
provider won't see the instance of {@code Configuration} we give it as being an instance of the
{@code Configuration} it's expecting (they're completely separate classes) and creation of the
file system will fail.
jimfs/src/test/java/com/google/common/jimfs/ClassLoaderTest.java