### Question:
RawChannel extends BaseChannel { protected int getMessageLength() throws IOException, ISOException { byte[] b = new byte[4]; serverIn.readFully(b,0,4); return ((int)b[0] &0xFF) << 24 | ((int)b[1] &0xFF) << 16 | ((int)b[2] &0xFF) << 8 | (int)b[3] &0xFF; } RawChannel();  RawChannel(String host, int port, ISOPackager p, byte[] header);  RawChannel(ISOPackager p, byte[] header);  RawChannel(ISOPackager p, byte[] header, ServerSocket serverSocket); void setHeader(String header);  }### Answer:
@Test public void testGetMessageLengthThrowsNullPointerException() throws Throwable { RawChannel rawChannel = new RawChannel(); try { rawChannel.getMessageLength(); fail("Expected NullPointerException to be thrown"); } catch (NullPointerException ex) { if (isJavaVersionAtMost(JAVA_14)) { assertNull(ex.getMessage(), "ex.getMessage()"); } else { assertEquals("Cannot invoke \"java.io.DataInputStream.readFully(byte[], int, int)\" because \"this.serverIn\" is null", ex.getMessage(), "ex.getMessage()"); } } }