### Question:
ReadableBuffers { public static String readAsString(ReadableBuffer buffer, Charset charset) { Preconditions.checkNotNull(charset, "charset"); byte[] bytes = readArray(buffer); return new String(bytes, charset); } private  ReadableBuffers(); static ReadableBuffer empty(); static ReadableBuffer wrap(byte[] bytes); static ReadableBuffer wrap(byte[] bytes, int offset, int length); static ReadableBuffer wrap(ByteBuffer bytes); static byte[] readArray(ReadableBuffer buffer); static String readAsString(ReadableBuffer buffer, Charset charset); static String readAsStringUtf8(ReadableBuffer buffer); static InputStream openStream(ReadableBuffer buffer, boolean owner); static ReadableBuffer ignoreClose(ReadableBuffer buffer);  }### Answer:
@Test(expected = NullPointerException.class) public void readAsString_checksNotNull() { ReadableBuffers.readAsString(null, UTF_8); }