### Question:
DigestScheme implements AuthScheme, Serializable { @Override public void processChallenge( final AuthChallenge authChallenge, final HttpContext context) throws MalformedChallengeException { Args.notNull(authChallenge, "AuthChallenge"); this.paramMap.clear(); final List<NameValuePair> params = authChallenge.getParams(); if (params != null) { for (final NameValuePair param: params) { this.paramMap.put(param.getName().toLowerCase(Locale.ROOT), param.getValue()); } } if (this.paramMap.isEmpty()) { throw new MalformedChallengeException("Missing digest auth parameters"); } this.complete = true; } DigestScheme();  DigestScheme(final Charset charset); void initPreemptive(final Credentials credentials, final String cnonce, final String realm); @Override String getName(); @Override boolean isConnectionBased(); @Override String getRealm(); @Override void processChallenge(
            final AuthChallenge authChallenge,
            final HttpContext context); @Override boolean isChallengeComplete(); @Override boolean isResponseReady(
            final HttpHost host,
            final CredentialsProvider credentialsProvider,
            final HttpContext context); @Override Principal getPrincipal(); @Override String generateAuthResponse(
            final HttpHost host,
            final HttpRequest request,
            final HttpContext context); @Internal String getNonce(); @Internal long getNounceCount(); @Internal String getCnonce(); @Override String toString();  }### Answer:
@Test(expected=MalformedChallengeException.class) public void testDigestAuthenticationEmptyChallenge1() throws Exception { final AuthChallenge authChallenge = parse(StandardAuthScheme.DIGEST); final AuthScheme authscheme = new DigestScheme(); authscheme.processChallenge(authChallenge, null); }
@Test(expected=MalformedChallengeException.class) public void testDigestAuthenticationEmptyChallenge2() throws Exception { final AuthChallenge authChallenge = parse(StandardAuthScheme.DIGEST + " "); final AuthScheme authscheme = new DigestScheme(); authscheme.processChallenge(authChallenge, null); }