diff --git a/acme4j-client/src/test/java/org/shredzone/acme4j/util/ClaimBuilderTest.java b/acme4j-client/src/test/java/org/shredzone/acme4j/util/ClaimBuilderTest.java
new file mode 100644
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--- /dev/null
+++ b/acme4j-client/src/test/java/org/shredzone/acme4j/util/ClaimBuilderTest.java
@@ -0,0 +1,182 @@
+/*
+ * acme4j - Java ACME client
+ *
+ * Copyright (C) 2015 Richard "Shred" Körber
+ *   http://acme4j.shredzone.org
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ */
+package org.shredzone.acme4j.util;
+
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.assertThat;
+
+import java.security.KeyPair;
+import java.security.KeyPairGenerator;
+import java.security.NoSuchAlgorithmException;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.jose4j.json.JsonUtil;
+import org.jose4j.lang.JoseException;
+import org.junit.Test;
+import org.shredzone.acme4j.connector.Resource;
+
+/**
+ * Unit test for {@link ClaimBuilder}.
+ *
+ * @author Richard "Shred" Körber
+ */
+public class ClaimBuilderTest {
+
+    /**
+     * Test that an empty claimbuilder is empty.
+     */
+    @Test
+    public void testEmpty() {
+        ClaimBuilder cb = new ClaimBuilder();
+        assertThat(cb.toString(), is("{}"));
+    }
+
+    /**
+     * Test basic data types. Also test that methods return {@code this}, that existing
+     * keys are replaced, and that the output keys are in lexicographical order.
+     */
+    @Test
+    public void testBasics() {
+        ClaimBuilder res;
+
+        ClaimBuilder cb = new ClaimBuilder();
+        res = cb.put("fooStr", "String");
+        assertThat(res, is(sameInstance(cb)));
+
+        res = cb.put("fooInt", 123);
+        assertThat(res, is(sameInstance(cb)));
+
+        res = cb.put("fooInt", 456);
+        assertThat(res, is(sameInstance(cb)));
+
+        assertThat(cb.toString(), is("{\"fooInt\":456,\"fooStr\":\"String\"}"));
+    }
+
+    /**
+     * Test resources.
+     */
+    @Test
+    public void testResource() {
+        ClaimBuilder res;
+
+        ClaimBuilder cb = new ClaimBuilder();
+        res = cb.putResource("new-reg");
+        assertThat(res, is(sameInstance(cb)));
+        assertThat(cb.toString(), is("{\"resource\":\"new-reg\"}"));
+
+        res = cb.putResource(Resource.NEW_AUTHZ);
+        assertThat(res, is(sameInstance(cb)));
+        assertThat(cb.toString(), is("{\"resource\":\"new-authz\"}"));
+    }
+
+    /**
+     * Test method to add maps.
+     */
+    @Test
+    public void testMap() {
+        Map<String, Object> map = new HashMap<>();
+        map.put("fooStr", "String");
+        map.put("fooInt", 123);
+
+        ClaimBuilder res;
+
+        ClaimBuilder cb = new ClaimBuilder();
+        res = cb.putAll(map);
+        assertThat(res, is(sameInstance(cb)));
+        assertThat(cb.toString(), is("{\"fooInt\":123,\"fooStr\":\"String\"}"));
+    }
+
+    /**
+     * Test base64 encoding.
+     */
+    @Test
+    public void testBase64() {
+        byte[] data = "abc123".getBytes();
+
+        ClaimBuilder res;
+
+        ClaimBuilder cb = new ClaimBuilder();
+        res = cb.putBase64("foo", data);
+        assertThat(res, is(sameInstance(cb)));
+        assertThat(cb.toString(), is("{\"foo\":\"YWJjMTIz\"}"));
+    }
+
+    /**
+     * Test JWK.
+     */
+    @Test
+    @SuppressWarnings("unchecked")
+    public void testKey() throws NoSuchAlgorithmException, JoseException {
+        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
+        keyGen.initialize(512);
+        KeyPair keyPair = keyGen.generateKeyPair();
+
+        ClaimBuilder res;
+
+        ClaimBuilder cb = new ClaimBuilder();
+        res = cb.putKey("foo", keyPair.getPublic());
+        assertThat(res, is(sameInstance(cb)));
+
+        Map<String, Object> json = JsonUtil.parseJson(cb.toString());
+        assertThat(json, hasKey("foo"));
+
+        Map<String, String> jwk = (Map<String, String>) json.get("foo");
+        assertThat(jwk.keySet(), hasSize(3));
+        assertThat(jwk.get("n"), not(isEmptyOrNullString()));
+        assertThat(jwk, hasEntry("e", "AQAB"));
+        assertThat(jwk, hasEntry("kty", "RSA"));
+    }
+
+    /**
+     * Test sub claims (objects).
+     */
+    @Test
+    public void testObject() {
+        ClaimBuilder cb = new ClaimBuilder();
+        ClaimBuilder sub = cb.object("sub");
+        assertThat(sub, not(sameInstance(cb)));
+
+        assertThat(cb.toString(), is("{\"sub\":{}}"));
+
+        cb.put("foo", 123);
+        sub.put("foo", 456);
+
+        assertThat(cb.toString(), is("{\"foo\":123,\"sub\":{\"foo\":456}}"));
+    }
+
+    /**
+     * Test arrays.
+     */
+    @Test
+    public void testArray() {
+        ClaimBuilder res;
+
+        ClaimBuilder cb1 = new ClaimBuilder();
+        res = cb1.array("ar", new Object[0]);
+        assertThat(res, is(sameInstance(cb1)));
+        assertThat(cb1.toString(), is("{\"ar\":[]}"));
+
+        ClaimBuilder cb2 = new ClaimBuilder();
+        res = cb2.array("ar", 123);
+        assertThat(res, is(sameInstance(cb2)));
+        assertThat(cb2.toString(), is("{\"ar\":[123]}"));
+
+        ClaimBuilder cb3 = new ClaimBuilder();
+        res = cb3.array("ar", 123, "foo", 456);
+        assertThat(res, is(sameInstance(cb3)));
+        assertThat(cb3.toString(), is("{\"ar\":[123,\"foo\",456]}"));
+    }
+
+}