final ObjectOutputStream out = mock(ObjectOutputStream.class);
final byte[] bytes = new byte[1];
bytes[0] = (byte) 0;
given(header.getLength()).willReturn(1);
given(header.pack()).willReturn(bytes);
iSOVMsg.writeHeader(out);
assertSame("(ISOVMsg) iSOVMsg.header", header, ((ISOVMsg) iSOVMsg).header);
verify(out).write(bytes);
verify(out).writeByte(72);