### Question:
AsyncTimeout extends Timeout { public final Source source(final Source source) { return new Source() { @Override public long read(Buffer sink, long byteCount) throws IOException { boolean throwOnTimeout = false; enter(); try { long result = source.read(sink, byteCount); throwOnTimeout = true; return result; } catch (IOException e) { throw exit(e); } finally { exit(throwOnTimeout); } } @Override public void close() throws IOException { boolean throwOnTimeout = false; try { source.close(); throwOnTimeout = true; } catch (IOException e) { throw exit(e); } finally { exit(throwOnTimeout); } } @Override public Timeout timeout() { return AsyncTimeout.this; } @Override public String toString() { return "AsyncTimeout.source(" + source + ")"; } }; }  final void enter(); final boolean exit(); final Sink sink(final Sink sink); final Source source(final Source source);  }### Answer:
@Test public void wrappedSourceTimesOut() throws Exception { Source source = new ForwardingSource(new Buffer()) { @Override public long read(Buffer sink, long byteCount) throws IOException { try { Thread.sleep(500); return -1; } catch (InterruptedException e) { throw new AssertionError(); } } }; AsyncTimeout timeout = new AsyncTimeout(); timeout.timeout(250, TimeUnit.MILLISECONDS); Source timeoutSource = timeout.source(source); try { timeoutSource.read(null, 0); fail(); } catch (InterruptedIOException expected) { } }