### Question:
ReadableBuffers { public static byte[] readArray(ReadableBuffer buffer) { Preconditions.checkNotNull(buffer, "buffer"); int length = buffer.readableBytes(); byte[] bytes = new byte[length]; buffer.readBytes(bytes, 0, length); return bytes; } 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 readArray_checksNotNull() { ReadableBuffers.readArray(null); }