JCK 6b b04
FAIL: JDK 7 b16 PASS JDK 7 b15; JDK6u4 b02

JCK test api/javax_xml/crypto/dsig/XMLSignature/index.html#methods[Signature2011] fails since JDK 7 b16. The problem is an internal implementation of XMLSignature violates statement from documentation:
"Throws:
    ClassCastException - if the type of validateContext is not compatible with this XMLSignature 
    NullPointerException - if validateContext is null "
and throws NPE even if validateContext is not null.

Steps to reproduce:

compile and run the following example:

import java.io.PrintWriter;
import java.security.InvalidAlgorithmParameterException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.AlgorithmParameterSpec;
import java.util.Collections;
import java.util.List;
import java.util.Vector;
import javax.xml.crypto.*;
import javax.xml.crypto.dsig.*;
import javax.xml.crypto.dsig.keyinfo.*;
import javax.xml.crypto.dsig.spec.*;


public class Crypto2 {

    public class MyXMLContext implements XMLValidateContext, XMLSignContext {
    
        MyXMLContext() {
        }
        
        public String getBaseURI() {
            return null;  
        }

        public void setBaseURI(String baseURI) {
        }

        public KeySelector getKeySelector() {
            return null;  
        }

        public void setKeySelector(KeySelector ks) {        
        }

        public URIDereferencer getURIDereferencer() {
            return null;  
        }

        public void setURIDereferencer(URIDereferencer dereferencer) {
        }

        public Object get(Object key) {
            return null;  
        }

        public Object getProperty(String name) {
            return null;  
        }

        public Object put(Object key, Object value) {
            return null;  
        }

        public Object setProperty(String name, Object value) {
            return null;  
        }
        
        public String getDefaultNamespacePrefix() {
            return null;
        }
        
        public void setDefaultNamespacePrefix(String defaultPrefix) {
        
        }
        
        public String putNamespacePrefix(String namespaceURI,
                                 String prefix) {
            return null;
        }                                 
        
        public String getNamespacePrefix(String namespaceURI,
                                 String defaultPrefix) {
            return "";                         
        }
        
        
    }
    

    protected XMLSignatureFactory getCurrentXMLFactory() 
	{
	try {
	    return XMLSignatureFactory.getInstance();
	} catch (Exception e) {
	    e.printStackTrace();
	    System.exit(1);
	    return null;
	}
	
    }

    protected XMLSignature getXMLSignature() {
    try {  
        XMLSignatureFactory xmlSignatureFactory = getCurrentXMLFactory();
        DigestMethod dm = xmlSignatureFactory.newDigestMethod(DigestMethod.SHA1, (DigestMethodParameterSpec) null);
        Reference ref1 = xmlSignatureFactory.newReference("", dm);
        CanonicalizationMethod cm = xmlSignatureFactory.newCanonicalizationMethod(CanonicalizationMethod.INCLUSIVE,(C14NMethodParameterSpec) null);
        SignatureMethod sm = xmlSignatureFactory.newSignatureMethod(SignatureMethod.DSA_SHA1, (SignatureMethodParameterSpec) null);
        SignedInfo si = xmlSignatureFactory.newSignedInfo(cm, sm, Collections.singletonList(ref1));
        KeyInfoFactory keyFactory = xmlSignatureFactory.getKeyInfoFactory();
        KeyInfo keyInfo = keyFactory.newKeyInfo (Collections.singletonList(keyFactory.newKeyName("mykey")), "myinfo");
        return xmlSignatureFactory.newXMLSignature(si, keyInfo);
        } catch (Exception e) {    
            System.out.println("Unexpected " + e);
        }
	System.exit(1);
        return null;
    }

    /* standalone interface */
    public static void main(String argv[]) {
        Crypto2 test = new Crypto2();
	test.Signature2011();
        
    }

    /**
     * Assertion testing
     * for public boolean validate(XMLValidateContext validateContext) throws XMLSignatureException,
     * ClassCastException will be thrown if the type of validateContext is not compatible with this XMLSignature.
     */
    public void Signature2011() {
        XMLSignature xmlSig = getXMLSignature();
        if (xmlSig != null) {
            try {
                xmlSig.validate(new MyXMLContext());
                System.out.println("ClassCastException was not thrown ");
            } catch (ClassCastException e) {
                e.printStackTrace();
            } catch (XMLSignatureException e) {
                e.printStackTrace();
            }
        }
    }
}

for different versions of JDK it will return different output:
for build 16:
C:\tests\crypto2>Z:\Links\stt\jdk_promotions\JDK7.0\b16\binaries\windows-i586\jdk1.7.0\bin\java.exe -cp . Crypto2
Exception in thread "main" java.lang.NullPointerException
        at org.jcp.xml.dsig.internal.dom.DOMXMLSignature$DOMSignatureValue.validate(DOMXMLSignature.java:516)
        at org.jcp.xml.dsig.internal.dom.DOMXMLSignature.validate(DOMXMLSignature.java:248)
        at Crypto2.Signature2011(Crypto2.java:126)
        at Crypto2.main(Crypto2.java:113)

for build 15:
C:\tests\crypto2>Z:\Links\stt\jdk_promotions\JDK7.0\b15\binaries\windows-i586\jdk1.7.0\bin\java.exe -cp . Crypto2
java.lang.ClassCastException: Crypto2$MyXMLContext cannot be cast to javax.xml.crypto.dom.DOMCryptoContext
        at org.jcp.xml.dsig.internal.dom.DOMURIDereferencer.dereference(DOMURIDereferencer.java:71)
        at org.jcp.xml.dsig.internal.dom.DOMReference.dereference(DOMReference.java:366)
        at org.jcp.xml.dsig.internal.dom.DOMReference.validate(DOMReference.java:333)
        at org.jcp.xml.dsig.internal.dom.DOMXMLSignature.validate(DOMXMLSignature.java:252)
        at Crypto2.Signature2011(Crypto2.java:126)
        at Crypto2.main(Crypto2.java:113)