### Question:
CertificateAuthorityCredential extends Certificate { public static Selector select(final CertificateManager certMan) { return new Selector(certMan); } CertificateAuthorityCredential(final byte[] certificateBytes);  CertificateAuthorityCredential(final Path certificatePath); protected  CertificateAuthorityCredential(); static Selector select(final CertificateManager certMan); String getCredentialType(); byte[] getSubjectKeyIdentifier(); @Override @SuppressWarnings("checkstyle:avoidinlineconditionals") boolean equals(final Object o); @Override @SuppressWarnings({"checkstyle:magicnumber", "checkstyle:avoidinlineconditionals"}) int hashCode(); static final String SUBJECT_KEY_IDENTIFIER_FIELD; }### Answer:
@Test(expectedExceptions = IllegalArgumentException.class) public void testSelectByNullSubjectKeyIdentifier() { CertificateAuthorityCredential.select(CERT_MAN).bySubjectKeyIdentifier(null); }
@Test(expectedExceptions = IllegalArgumentException.class) public void testSelectByEmptySubjectKeyIdentifier() { CertificateAuthorityCredential.select(CERT_MAN).bySubjectKeyIdentifier(new byte[]{}); }