### Question:
ISOFieldPackager { protected byte[] readBytes (InputStream in, int l) throws IOException { byte[] b = new byte [l]; int n = 0; while (n < l) { int count = in.read(b, n, l - n); if (count < 0) throw new EOFException(); n += count; } return b; } ISOFieldPackager();  ISOFieldPackager(int len, String description); String getDescription(); void setDescription(String description); int getLength(); void setLength(int len); void setPad(boolean pad); void setTrim(boolean trim); abstract int getMaxPackedLength(); ISOComponent createComponent(int fieldNumber); abstract byte[] pack(ISOComponent c); abstract int unpack(ISOComponent c, byte[] b, int offset); void unpack(ISOComponent c, InputStream in); void pack(ISOComponent c, ObjectOutput out);  }### Answer:
@Test public void testReadBytes() throws Throwable { ISOFieldPackager iFB_LLHFBINARY = new IFB_LLHFBINARY(100, "testISOFieldPackagerDescription"); byte[] bytes = new byte[1]; byte[] result = iFB_LLHFBINARY.readBytes(new ByteArrayInputStream(bytes), 1); assertEquals(1, result.length, "result.length"); assertEquals((byte) 0, result[0], "result[0]"); }
@Test public void testReadBytes1() throws Throwable { ISOFieldPackager iFB_AMOUNT = new IFB_AMOUNT(); byte[] result = iFB_AMOUNT.readBytes(new ByteArrayInputStream("testString".getBytes()), 0); assertEquals(0, result.length, "result.length"); }
@Test public void testReadBytesThrowsEOFException() throws Throwable { ISOFieldPackager iFA_BINARY = new IFA_BINARY(100, "testISOFieldPackagerDescription"); byte[] bytes = new byte[1]; InputStream in = new ByteArrayInputStream(bytes); try { iFA_BINARY.readBytes(in, 100); fail("Expected EOFException to be thrown"); } catch (EOFException ex) { assertEquals(EOFException.class, ex.getClass(), "ex.getClass()"); assertEquals(0, in.available(), "(ByteArrayInputStream) in.available()"); } }
@Test public void testReadBytesThrowsNegativeArraySizeException() throws Throwable { InputStream in = new ByteArrayInputStream("testString".getBytes()); ISOFieldPackager iFEB_LLLNUM = new IFEB_LLLNUM(); try { iFEB_LLLNUM.readBytes(in, -1); fail("Expected NegativeArraySizeException to be thrown"); } catch (NegativeArraySizeException ex) { if (isJavaVersionAtMost(JAVA_10)) { assertNull(ex.getMessage(), "ex.getMessage()"); } else { assertEquals("-1", ex.getMessage(), "ex.getMessage()"); } assertEquals(10, in.available(), "(ByteArrayInputStream) in.available()"); } }
@Test public void testReadBytesThrowsNullPointerException() throws Throwable { ISOFieldPackager iFA_FLLCHAR = new IFA_FLLCHAR(0, "testISOFieldPackagerDescription"); try { iFA_FLLCHAR.readBytes(null, 100); fail("Expected NullPointerException to be thrown"); } catch (NullPointerException ex) { if (isJavaVersionAtMost(JAVA_14)) { assertNull(ex.getMessage(), "ex.getMessage()"); } else { assertEquals("Cannot invoke \"java.io.InputStream.read(byte[], int, int)\" because \"in\" is null", ex.getMessage(), "ex.getMessage()"); } } }