### Question:
EncryptedPIN implements Serializable, Loggeable { public static String extractAccountNumberPart (String accountNumber) { String accountNumberPart = null; try { accountNumberPart = ISOUtil.takeLastN(accountNumber, 13); accountNumberPart = ISOUtil.takeFirstN(accountNumberPart, 12); } catch(ISOException ignored) { } return accountNumberPart; } EncryptedPIN();  EncryptedPIN(byte[] pinBlock, byte pinBlockFormat, String accountNumber);  EncryptedPIN(byte[] pinBlock, byte pinBlockFormat, String accountNumber, boolean extract);  EncryptedPIN(String pinBlockHexString, byte pinBlockFormat, String accountNumber);  EncryptedPIN(String pinBlockHexString, byte pinBlockFormat, String accountNumber, boolean extract); void dump(PrintStream p, String indent); void setPINBlock(byte[] pinBlock); byte[] getPINBlock(); void setPINBlockFormat(byte pinBlockFormat); byte getPINBlockFormat(); void setAccountNumber(String extractedAccountNumber); String getAccountNumber(); static String extractAccountNumberPart(String accountNumber);  }### Answer:
@Test public void testExtractAccountNumberPart() throws Throwable { String result = EncryptedPIN.extractAccountNumberPart("11Character"); assertEquals("0011Characte", result, "result"); }
@Test public void testExtractAccountNumberPart1() throws Throwable { String result = EncryptedPIN.extractAccountNumberPart("13CharactersX"); assertEquals("13Characters", result, "result"); }
@Test public void testExtractAccountNumberPart2() throws Throwable { String result = EncryptedPIN.extractAccountNumberPart("12Characters"); assertEquals("012Character", result, "result"); }
@Test public void testExtractAccountNumberPartThrowsNullPointerException() throws Throwable { try { EncryptedPIN.extractAccountNumberPart(null); fail("Expected NullPointerException to be thrown"); } catch (NullPointerException ex) { if (isJavaVersionAtMost(JAVA_14)) { assertNull(ex.getMessage(), "ex.getMessage()"); } else { assertEquals("Cannot invoke \"String.length()\" because \"s\" is null", ex.getMessage(), "ex.getMessage()"); } } }