Merge branch 'max-client-id-length' into 'master'

Set max length for client IDs

See merge request akwizgran/briar!762

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/TransportId.java

@@ -1,22 +1,23 @@
 package org.briarproject.bramble.api.plugin;
 
-import java.nio.charset.Charset;
+import org.briarproject.bramble.util.StringUtils;
 
 /**
- * Type-safe wrapper for a string that uniquely identifies a transport plugin.
+ * Type-safe wrapper for a namespaced string that uniquely identifies a
+ * transport plugin.
  */
 public class TransportId {
 
 	/**
-	 * The maximum length of transport identifier in UTF-8 bytes.
+	 * The maximum length of a transport identifier in UTF-8 bytes.
 	 */
-	public static int MAX_TRANSPORT_ID_LENGTH = 64;
+	public static int MAX_TRANSPORT_ID_LENGTH = 100;
 
 	private final String id;
 
 	public TransportId(String id) {
-		byte[] b = id.getBytes(Charset.forName("UTF-8"));
-		if (b.length == 0 || b.length > MAX_TRANSPORT_ID_LENGTH)
+		int length = StringUtils.toUtf8(id).length;
+		if (length == 0 || length > MAX_TRANSPORT_ID_LENGTH)
 			throw new IllegalArgumentException();
 		this.id = id;
 	}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/ClientId.java

@@ -1,19 +1,29 @@
 package org.briarproject.bramble.api.sync;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.StringUtils;
 
 import javax.annotation.concurrent.Immutable;
 
 /**
- * Wrapper for a name-spaced string that uniquely identifies a sync client.
+ * Type-safe wrapper for a namespaced string that uniquely identifies a sync
+ * client.
  */
 @Immutable
 @NotNullByDefault
 public class ClientId implements Comparable<ClientId> {
 
+	/**
+	 * The maximum length of a client identifier in UTF-8 bytes.
+	 */
+	public static int MAX_CLIENT_ID_LENGTH = 100;
+
 	private final String id;
 
 	public ClientId(String id) {
+		int length = StringUtils.toUtf8(id).length;
+		if (length == 0 || length > MAX_CLIENT_ID_LENGTH)
+			throw new IllegalArgumentException();
 		this.id = id;
 	}
 

bramble-api/src/test/java/org/briarproject/bramble/test/TestUtils.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.identity.LocalAuthor;
+import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupId;
@@ -23,6 +24,8 @@ import java.util.concurrent.atomic.AtomicInteger;
 import static org.briarproject.bramble.api.identity.Author.FORMAT_VERSION;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
+import static org.briarproject.bramble.api.plugin.TransportId.MAX_TRANSPORT_ID_LENGTH;
+import static org.briarproject.bramble.api.sync.ClientId.MAX_CLIENT_ID_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_GROUP_DESCRIPTOR_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
@@ -54,6 +57,14 @@ public class TestUtils {
 		return getRandomBytes(UniqueId.LENGTH);
 	}
 
+	public static ClientId getClientId() {
+		return new ClientId(getRandomString(MAX_CLIENT_ID_LENGTH));
+	}
+
+	public static TransportId getTransportId() {
+		return new TransportId(getRandomString(MAX_TRANSPORT_ID_LENGTH));
+	}
+
 	public static SecretKey getSecretKey() {
 		return new SecretKey(getRandomBytes(SecretKey.LENGTH));
 	}

bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyDerivationTest.java

@@ -17,6 +17,7 @@ import java.util.List;
 import java.util.Set;
 
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
@@ -27,7 +28,7 @@ public class KeyDerivationTest extends BrambleTestCase {
 			new CryptoComponentImpl(new TestSecureRandomProvider(), null);
 	private final TransportCrypto transportCrypto =
 			new TransportCryptoImpl(crypto);
-	private final TransportId transportId = new TransportId("id");
+	private final TransportId transportId = getTransportId();
 	private final SecretKey master = getSecretKey();
 
 	@Test
@@ -135,7 +136,7 @@ public class KeyDerivationTest extends BrambleTestCase {
 
 	@Test
 	public void testTransportIdAffectsOutput() {
-		TransportId transportId1 = new TransportId("id1");
+		TransportId transportId1 = getTransportId();
 		assertFalse(transportId.getString().equals(transportId1.getString()));
 		TransportKeys k = transportCrypto.deriveTransportKeys(transportId,
 				master, 123, true, true);

bramble-core/src/test/java/org/briarproject/bramble/db/DatabaseComponentImplTest.java

@@ -50,7 +50,6 @@ import org.briarproject.bramble.api.transport.OutgoingKeys;
 import org.briarproject.bramble.api.transport.TransportKeys;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.CaptureArgumentAction;
-import org.briarproject.bramble.test.TestUtils;
 import org.jmock.Expectations;
 import org.junit.Test;
 
@@ -64,15 +63,17 @@ import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.Group.Visibility.VISIBLE;
-import static org.briarproject.bramble.api.sync.SyncConstants.MAX_GROUP_DESCRIPTOR_LENGTH;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.DELIVERED;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.UNKNOWN;
 import static org.briarproject.bramble.api.transport.TransportConstants.REORDERING_WINDOW_SIZE;
 import static org.briarproject.bramble.db.DatabaseConstants.MAX_OFFERED_MESSAGES;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
-import static org.briarproject.bramble.util.StringUtils.getRandomString;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -104,21 +105,20 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 	private final KeySetId keySetId;
 
 	public DatabaseComponentImplTest() {
-		clientId = new ClientId(getRandomString(123));
-		groupId = new GroupId(TestUtils.getRandomId());
-		byte[] descriptor = new byte[MAX_GROUP_DESCRIPTOR_LENGTH];
-		group = new Group(groupId, clientId, descriptor);
+		clientId = getClientId();
+		group = getGroup(clientId);
+		groupId = group.getId();
 		author = getAuthor();
 		localAuthor = getLocalAuthor();
-		messageId = new MessageId(TestUtils.getRandomId());
-		messageId1 = new MessageId(TestUtils.getRandomId());
+		messageId = new MessageId(getRandomId());
+		messageId1 = new MessageId(getRandomId());
 		long timestamp = System.currentTimeMillis();
 		size = 1234;
 		raw = new byte[size];
 		message = new Message(messageId, groupId, timestamp, raw);
 		metadata = new Metadata();
 		metadata.put("foo", new byte[] {'b', 'a', 'r'});
-		transportId = new TransportId("id");
+		transportId = getTransportId();
 		maxLatency = Integer.MAX_VALUE;
 		contactId = new ContactId(234);
 		contact = new Contact(contactId, author, localAuthor.getId(),
@@ -919,7 +919,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testGenerateOffer() throws Exception {
-		MessageId messageId1 = new MessageId(TestUtils.getRandomId());
+		MessageId messageId1 = new MessageId(getRandomId());
 		Collection<MessageId> ids = Arrays.asList(messageId, messageId1);
 		context.checking(new Expectations() {{
 			oneOf(database).startTransaction();
@@ -950,7 +950,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testGenerateRequest() throws Exception {
-		MessageId messageId1 = new MessageId(TestUtils.getRandomId());
+		MessageId messageId1 = new MessageId(getRandomId());
 		Collection<MessageId> ids = Arrays.asList(messageId, messageId1);
 		context.checking(new Expectations() {{
 			oneOf(database).startTransaction();
@@ -1138,9 +1138,9 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testReceiveOffer() throws Exception {
-		MessageId messageId1 = new MessageId(TestUtils.getRandomId());
-		MessageId messageId2 = new MessageId(TestUtils.getRandomId());
-		MessageId messageId3 = new MessageId(TestUtils.getRandomId());
+		MessageId messageId1 = new MessageId(getRandomId());
+		MessageId messageId2 = new MessageId(getRandomId());
+		MessageId messageId3 = new MessageId(getRandomId());
 		context.checking(new Expectations() {{
 			oneOf(database).startTransaction();
 			will(returnValue(txn));
@@ -1508,7 +1508,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 	@SuppressWarnings("unchecked")
 	public void testMessageDependencies() throws Exception {
 		int shutdownHandle = 12345;
-		MessageId messageId2 = new MessageId(TestUtils.getRandomId());
+		MessageId messageId2 = new MessageId(getRandomId());
 		context.checking(new Expectations() {{
 			// open()
 			oneOf(database).open(null);

bramble-core/src/test/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

@@ -52,18 +52,19 @@ import static org.briarproject.bramble.api.db.Metadata.REMOVE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.Group.Visibility.VISIBLE;
-import static org.briarproject.bramble.api.sync.SyncConstants.MAX_GROUP_DESCRIPTOR_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_LENGTH;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.DELIVERED;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.INVALID;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.PENDING;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.UNKNOWN;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
-import static org.briarproject.bramble.util.StringUtils.getRandomString;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -94,10 +95,9 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private final KeySetId keySetId, keySetId1;
 
 	JdbcDatabaseTest() throws Exception {
-		groupId = new GroupId(getRandomId());
-		clientId = new ClientId(getRandomString(123));
-		byte[] descriptor = new byte[MAX_GROUP_DESCRIPTOR_LENGTH];
-		group = new Group(groupId, clientId, descriptor);
+		clientId = getClientId();
+		group = getGroup(clientId);
+		groupId = group.getId();
 		author = getAuthor();
 		localAuthor = getLocalAuthor();
 		messageId = new MessageId(getRandomId());
@@ -105,7 +105,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		size = 1234;
 		raw = getRandomBytes(size);
 		message = new Message(messageId, groupId, timestamp, raw);
-		transportId = new TransportId("id");
+		transportId = getTransportId();
 		contactId = new ContactId(1);
 		keySetId = new KeySetId(1);
 		keySetId1 = new KeySetId(2);
@@ -1407,9 +1407,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.addMessage(txn, message, PENDING, true, contactId);
 
 		// Add a second group
-		GroupId groupId1 = new GroupId(getRandomId());
-		Group group1 = new Group(groupId1, clientId,
-				getRandomBytes(MAX_GROUP_DESCRIPTOR_LENGTH));
+		Group group1 = getGroup(clientId);
+		GroupId groupId1 = group1.getId();
 		db.addGroup(txn, group1);
 
 		// Add a message to the second group

bramble-core/src/test/java/org/briarproject/bramble/keyagreement/KeyAgreementTransportTest.java

@@ -19,6 +19,7 @@ import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.RE
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.ABORT;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.CONFIRM;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.KEY;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 
@@ -31,7 +32,7 @@ public class KeyAgreementTransportTest extends BrambleMockTestCase {
 	private final TransportConnectionWriter transportConnectionWriter =
 			context.mock(TransportConnectionWriter.class);
 
-	private final TransportId transportId = new TransportId("test");
+	private final TransportId transportId = getTransportId();
 	private final KeyAgreementConnection keyAgreementConnection =
 			new KeyAgreementConnection(duplexTransportConnection, transportId);
 

bramble-core/src/test/java/org/briarproject/bramble/plugin/ConnectionRegistryImplTest.java

@@ -17,6 +17,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.NoSuchElementException;
 
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -29,8 +30,8 @@ public class ConnectionRegistryImplTest extends BrambleTestCase {
 	public ConnectionRegistryImplTest() {
 		contactId = new ContactId(1);
 		contactId1 = new ContactId(2);
-		transportId = new TransportId("id");
-		transportId1 = new TransportId("id1");
+		transportId = getTransportId();
+		transportId1 = getTransportId();
 	}
 
 	@Test

bramble-core/src/test/java/org/briarproject/bramble/plugin/PluginManagerImplTest.java

@@ -24,6 +24,8 @@ import java.util.Arrays;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
 
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
+
 public class PluginManagerImplTest extends BrambleTestCase {
 
 	@Test
@@ -46,21 +48,21 @@ public class PluginManagerImplTest extends BrambleTestCase {
 		SimplexPluginFactory simplexFactory =
 				context.mock(SimplexPluginFactory.class);
 		SimplexPlugin simplexPlugin = context.mock(SimplexPlugin.class);
-		TransportId simplexId = new TransportId("simplex");
+		TransportId simplexId = getTransportId();
 		SimplexPluginFactory simplexFailFactory =
 				context.mock(SimplexPluginFactory.class, "simplexFailFactory");
 		SimplexPlugin simplexFailPlugin =
 				context.mock(SimplexPlugin.class, "simplexFailPlugin");
-		TransportId simplexFailId = new TransportId("simplex1");
+		TransportId simplexFailId = getTransportId();
 
 		// Two duplex plugin factories: one creates a plugin, the other fails
 		DuplexPluginFactory duplexFactory =
 				context.mock(DuplexPluginFactory.class);
 		DuplexPlugin duplexPlugin = context.mock(DuplexPlugin.class);
-		TransportId duplexId = new TransportId("duplex");
+		TransportId duplexId = getTransportId();
 		DuplexPluginFactory duplexFailFactory =
 				context.mock(DuplexPluginFactory.class, "duplexFailFactory");
-		TransportId duplexFailId = new TransportId("duplex1");
+		TransportId duplexFailId = getTransportId();
 
 		context.checking(new Expectations() {{
 			allowing(simplexPlugin).getId();

bramble-core/src/test/java/org/briarproject/bramble/plugin/PollerTest.java

@@ -32,6 +32,7 @@ import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 
 public class PollerTest extends BrambleMockTestCase {
 
@@ -48,7 +49,7 @@ public class PollerTest extends BrambleMockTestCase {
 	private final SecureRandom random;
 
 	private final Executor ioExecutor = new ImmediateExecutor();
-	private final TransportId transportId = new TransportId("id");
+	private final TransportId transportId = getTransportId();
 	private final ContactId contactId = new ContactId(234);
 	private final int pollingInterval = 60 * 1000;
 	private final long now = System.currentTimeMillis();
@@ -64,7 +65,7 @@ public class PollerTest extends BrambleMockTestCase {
 		SimplexPlugin simplexPlugin = context.mock(SimplexPlugin.class);
 		SimplexPlugin simplexPlugin1 =
 				context.mock(SimplexPlugin.class, "simplexPlugin1");
-		TransportId simplexId1 = new TransportId("simplex1");
+		TransportId simplexId1 = getTransportId();
 		List<SimplexPlugin> simplexPlugins = Arrays.asList(simplexPlugin,
 				simplexPlugin1);
 		TransportConnectionWriter simplexWriter =
@@ -72,7 +73,7 @@ public class PollerTest extends BrambleMockTestCase {
 
 		// Two duplex plugins: one supports polling, the other doesn't
 		DuplexPlugin duplexPlugin = context.mock(DuplexPlugin.class);
-		TransportId duplexId = new TransportId("duplex");
+		TransportId duplexId = getTransportId();
 		DuplexPlugin duplexPlugin1 =
 				context.mock(DuplexPlugin.class, "duplexPlugin1");
 		List<DuplexPlugin> duplexPlugins = Arrays.asList(duplexPlugin,
@@ -349,7 +350,6 @@ public class PollerTest extends BrambleMockTestCase {
 	@Test
 	public void testCancelsPollingOnTransportDisabled() throws Exception {
 		Plugin plugin = context.mock(Plugin.class);
-		List<ContactId> connected = Collections.singletonList(contactId);
 
 		context.checking(new Expectations() {{
 			allowing(plugin).getId();

bramble-core/src/test/java/org/briarproject/bramble/properties/TransportPropertyManagerImplTest.java

@@ -32,9 +32,9 @@ import java.util.Map;
 import static org.briarproject.bramble.api.properties.TransportPropertyManager.CLIENT_ID;
 import static org.briarproject.bramble.api.properties.TransportPropertyManager.CLIENT_VERSION;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
-import static org.briarproject.bramble.api.sync.SyncConstants.MAX_GROUP_DESCRIPTOR_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_LENGTH;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
@@ -51,7 +51,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			context.mock(ContactGroupFactory.class);
 	private final Clock clock = context.mock(Clock.class);
 
-	private final Group localGroup = getGroup();
+	private final Group localGroup = getGroup(CLIENT_ID);
 	private final LocalAuthor localAuthor = getLocalAuthor();
 	private final BdfDictionary fooPropertiesDict = BdfDictionary.of(
 			new BdfEntry("fooKey1", "fooValue1"),
@@ -90,7 +90,8 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		Contact contact1 = getContact(true);
 		Contact contact2 = getContact(true);
 		List<Contact> contacts = Arrays.asList(contact1, contact2);
-		Group contactGroup1 = getGroup(), contactGroup2 = getGroup();
+		Group contactGroup1 = getGroup(CLIENT_ID);
+		Group contactGroup2 = getGroup(CLIENT_ID);
 
 		context.checking(new Expectations() {{
 			oneOf(db).containsGroup(txn, localGroup.getId());
@@ -143,7 +144,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	public void testCreatesContactGroupWhenAddingContact() throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup();
+		Group contactGroup = getGroup(CLIENT_ID);
 
 		context.checking(new Expectations() {{
 			// Create the group and share it with the contact
@@ -171,7 +172,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	public void testRemovesGroupWhenRemovingContact() throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup();
+		Group contactGroup = getGroup(CLIENT_ID);
 
 		context.checking(new Expectations() {{
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
@@ -306,7 +307,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	@Test
 	public void testStoresRemotePropertiesWithVersion0() throws Exception {
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup();
+		Group contactGroup = getGroup(CLIENT_ID);
 		Transaction txn = new Transaction(null, false);
 		Map<TransportId, TransportProperties> properties =
 				new LinkedHashMap<>();
@@ -417,8 +418,8 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		Contact contact3 = getContact(true);
 		List<Contact> contacts =
 				Arrays.asList(contact1, contact2, contact3);
-		Group contactGroup2 = getGroup();
-		Group contactGroup3 = getGroup();
+		Group contactGroup2 = getGroup(CLIENT_ID);
+		Group contactGroup3 = getGroup(CLIENT_ID);
 		Map<MessageId, BdfDictionary> messageMetadata3 =
 				new LinkedHashMap<>();
 		// A remote update for another transport should be ignored
@@ -514,7 +515,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	public void testMergingNewPropertiesCreatesUpdate() throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup();
+		Group contactGroup = getGroup(CLIENT_ID);
 
 		context.checking(new Expectations() {{
 			oneOf(db).startTransaction(false);
@@ -549,7 +550,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	public void testMergingUpdatedPropertiesCreatesUpdate() throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup();
+		Group contactGroup = getGroup(CLIENT_ID);
 		BdfDictionary oldMetadata = BdfDictionary.of(
 				new BdfEntry("transportId", "foo"),
 				new BdfEntry("version", 1),
@@ -600,12 +601,6 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		t.mergeLocalProperties(new TransportId("foo"), fooProperties);
 	}
 
-	private Group getGroup() {
-		GroupId g = new GroupId(getRandomId());
-		byte[] descriptor = getRandomBytes(MAX_GROUP_DESCRIPTOR_LENGTH);
-		return new Group(g, CLIENT_ID, descriptor);
-	}
-
 	private Contact getContact(boolean active) {
 		ContactId c = new ContactId(nextContactId++);
 		return new Contact(c, getAuthor(), localAuthor.getId(),

bramble-core/src/test/java/org/briarproject/bramble/properties/TransportPropertyValidatorTest.java

@@ -6,14 +6,11 @@ import org.briarproject.bramble.api.data.BdfDictionary;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.data.MetadataEncoder;
 import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.test.BrambleTestCase;
-import org.briarproject.bramble.test.TestUtils;
 import org.briarproject.bramble.util.StringUtils;
 import org.jmock.Mockery;
 import org.junit.Test;
@@ -22,6 +19,11 @@ import java.io.IOException;
 
 import static org.briarproject.bramble.api.plugin.TransportId.MAX_TRANSPORT_ID_LENGTH;
 import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MAX_PROPERTIES_PER_TRANSPORT;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertEquals;
 
 public class TransportPropertyValidatorTest extends BrambleTestCase {
@@ -33,18 +35,14 @@ public class TransportPropertyValidatorTest extends BrambleTestCase {
 	private final TransportPropertyValidator tpv;
 
 	public TransportPropertyValidatorTest() {
-		transportId = new TransportId("test");
+		transportId = getTransportId();
 		bdfDictionary = new BdfDictionary();
 
-		GroupId groupId = new GroupId(TestUtils.getRandomId());
-		ClientId clientId = new ClientId(StringUtils.getRandomString(5));
-		byte[] descriptor = TestUtils.getRandomBytes(12);
-		group = new Group(groupId, clientId, descriptor);
-
-		MessageId messageId = new MessageId(TestUtils.getRandomId());
+		group = getGroup(getClientId());
+		MessageId messageId = new MessageId(getRandomId());
 		long timestamp = System.currentTimeMillis();
-		byte[] body = TestUtils.getRandomBytes(123);
-		message = new Message(messageId, groupId, timestamp, body);
+		byte[] body = getRandomBytes(123);
+		message = new Message(messageId, group.getId(), timestamp, body);
 
 		Mockery context = new Mockery();
 		ClientHelper clientHelper = context.mock(ClientHelper.class);
@@ -63,7 +61,7 @@ public class TransportPropertyValidatorTest extends BrambleTestCase {
 		BdfDictionary result = tpv.validateMessage(message, group, body)
 				.getDictionary();
 
-		assertEquals("test", result.getString("transportId"));
+		assertEquals(transportId.getString(), result.getString("transportId"));
 		assertEquals(4, result.getLong("version").longValue());
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/sync/SyncIntegrationTest.java

@@ -36,7 +36,8 @@ import javax.inject.Inject;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_GROUP_DESCRIPTOR_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.PROTOCOL_VERSION;
 import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
-import static org.briarproject.bramble.util.StringUtils.getRandomString;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -73,13 +74,13 @@ public class SyncIntegrationTest extends BrambleTestCase {
 		component.inject(this);
 
 		contactId = new ContactId(234);
-		transportId = new TransportId("id");
+		transportId = getTransportId();
 		// Create the transport keys
 		tagKey = TestUtils.getSecretKey();
 		headerKey = TestUtils.getSecretKey();
 		streamNumber = 123;
 		// Create a group
-		ClientId clientId = new ClientId(getRandomString(123));
+		ClientId clientId = getClientId();
 		int clientVersion = 1234567890;
 		byte[] descriptor = new byte[MAX_GROUP_DESCRIPTOR_LENGTH];
 		Group group = groupFactory.createGroup(clientId, clientVersion,

bramble-core/src/test/java/org/briarproject/bramble/sync/ValidationManagerImplTest.java

@@ -21,9 +21,7 @@ import org.briarproject.bramble.api.sync.ValidationManager.State;
 import org.briarproject.bramble.api.sync.event.MessageAddedEvent;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.ImmediateExecutor;
-import org.briarproject.bramble.test.TestUtils;
 import org.briarproject.bramble.util.ByteUtils;
-import org.briarproject.bramble.util.StringUtils;
 import org.jmock.Expectations;
 import org.junit.Before;
 import org.junit.Test;
@@ -38,6 +36,9 @@ import static org.briarproject.bramble.api.sync.ValidationManager.State.DELIVERE
 import static org.briarproject.bramble.api.sync.ValidationManager.State.INVALID;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.PENDING;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.UNKNOWN;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
 
 public class ValidationManagerImplTest extends BrambleMockTestCase {
 
@@ -51,14 +52,12 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 
 	private final Executor dbExecutor = new ImmediateExecutor();
 	private final Executor validationExecutor = new ImmediateExecutor();
-	private final ClientId clientId =
-			new ClientId(StringUtils.getRandomString(5));
-	private final MessageId messageId = new MessageId(TestUtils.getRandomId());
-	private final MessageId messageId1 = new MessageId(TestUtils.getRandomId());
-	private final MessageId messageId2 = new MessageId(TestUtils.getRandomId());
-	private final GroupId groupId = new GroupId(TestUtils.getRandomId());
-	private final byte[] descriptor = new byte[32];
-	private final Group group = new Group(groupId, clientId, descriptor);
+	private final ClientId clientId = getClientId();
+	private final MessageId messageId = new MessageId(getRandomId());
+	private final MessageId messageId1 = new MessageId(getRandomId());
+	private final MessageId messageId2 = new MessageId(getRandomId());
+	private final Group group = getGroup(clientId);
+	private final GroupId groupId = group.getId();
 	private final long timestamp = System.currentTimeMillis();
 	private final byte[] raw = new byte[123];
 	private final Message message = new Message(messageId, groupId, timestamp,
@@ -716,8 +715,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testRecursiveInvalidation() throws Exception {
-		MessageId messageId3 = new MessageId(TestUtils.getRandomId());
-		MessageId messageId4 = new MessageId(TestUtils.getRandomId());
+		MessageId messageId3 = new MessageId(getRandomId());
+		MessageId messageId4 = new MessageId(getRandomId());
 		Map<MessageId, State> twoDependents = new LinkedHashMap<>();
 		twoDependents.put(messageId1, PENDING);
 		twoDependents.put(messageId2, PENDING);
@@ -819,8 +818,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testPendingDependentsGetDelivered() throws Exception {
-		MessageId messageId3 = new MessageId(TestUtils.getRandomId());
-		MessageId messageId4 = new MessageId(TestUtils.getRandomId());
+		MessageId messageId3 = new MessageId(getRandomId());
+		MessageId messageId4 = new MessageId(getRandomId());
 		Message message3 = new Message(messageId3, groupId, timestamp,
 				raw);
 		Message message4 = new Message(messageId4, groupId, timestamp,

bramble-core/src/test/java/org/briarproject/bramble/test/TestPluginConfigModule.java

@@ -16,10 +16,12 @@ import javax.annotation.Nullable;
 import dagger.Module;
 import dagger.Provides;
 
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
+
 @Module
 public class TestPluginConfigModule {
 
-	public static final TransportId TRANSPORT_ID = new TransportId("id");
+	public static final TransportId TRANSPORT_ID = getTransportId();
 	public static final int MAX_LATENCY = 2 * 60 * 1000; // 2 minutes
 
 	@NotNullByDefault

bramble-core/src/test/java/org/briarproject/bramble/test/ValidatorTestCase.java

@@ -2,17 +2,16 @@ package org.briarproject.bramble.test;
 
 import org.briarproject.bramble.api.client.ClientHelper;
 import org.briarproject.bramble.api.data.MetadataEncoder;
-import org.briarproject.bramble.api.identity.AuthorFactory;
-import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.system.Clock;
 
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
-import static org.briarproject.bramble.util.StringUtils.getRandomString;
 
 public abstract class ValidatorTestCase extends BrambleMockTestCase {
 
@@ -21,17 +20,14 @@ public abstract class ValidatorTestCase extends BrambleMockTestCase {
 	protected final MetadataEncoder metadataEncoder =
 			context.mock(MetadataEncoder.class);
 	protected final Clock clock = context.mock(Clock.class);
-	protected final AuthorFactory authorFactory =
-			context.mock(AuthorFactory.class);
 
+	protected final Group group = getGroup(getClientId());
+	protected final GroupId groupId = group.getId();
+	protected final byte[] descriptor = group.getDescriptor();
 	protected final MessageId messageId = new MessageId(getRandomId());
-	protected final GroupId groupId = new GroupId(getRandomId());
 	protected final long timestamp = 1234567890 * 1000L;
 	protected final byte[] raw = getRandomBytes(123);
 	protected final Message message =
 			new Message(messageId, groupId, timestamp, raw);
-	protected final ClientId clientId = new ClientId(getRandomString(123));
-	protected final byte[] descriptor = getRandomBytes(123);
-	protected final Group group = new Group(groupId, clientId, descriptor);
 
 }

bramble-core/src/test/java/org/briarproject/bramble/transport/KeyManagerImplTest.java

@@ -31,6 +31,7 @@ import static org.briarproject.bramble.test.TestUtils.getAuthor;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertEquals;
 
 public class KeyManagerImplTest extends BrambleMockTestCase {
@@ -47,8 +48,8 @@ public class KeyManagerImplTest extends BrambleMockTestCase {
 	private final ContactId contactId = new ContactId(123);
 	private final ContactId inactiveContactId = new ContactId(234);
 	private final KeySetId keySetId = new KeySetId(345);
-	private final TransportId transportId = new TransportId("known");
-	private final TransportId unknownTransportId = new TransportId("unknown");
+	private final TransportId transportId = getTransportId();
+	private final TransportId unknownTransportId = getTransportId();
 	private final StreamContext streamContext =
 			new StreamContext(contactId, transportId, getSecretKey(),
 					getSecretKey(), 1);

bramble-core/src/test/java/org/briarproject/bramble/transport/TransportKeyManagerImplTest.java

@@ -36,6 +36,7 @@ import static org.briarproject.bramble.api.transport.TransportConstants.MAX_CLOC
 import static org.briarproject.bramble.api.transport.TransportConstants.PROTOCOL_VERSION;
 import static org.briarproject.bramble.api.transport.TransportConstants.REORDERING_WINDOW_SIZE;
 import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.briarproject.bramble.util.ByteUtils.MAX_32_BIT_UNSIGNED;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -53,7 +54,7 @@ public class TransportKeyManagerImplTest extends BrambleMockTestCase {
 			context.mock(ScheduledExecutorService.class);
 	private final Clock clock = context.mock(Clock.class);
 
-	private final TransportId transportId = new TransportId("id");
+	private final TransportId transportId = getTransportId();
 	private final long maxLatency = 30 * 1000; // 30 seconds
 	private final long rotationPeriodLength = maxLatency + MAX_CLOCK_DIFFERENCE;
 	private final ContactId contactId = new ContactId(123);

briar-core/src/test/java/org/briarproject/briar/blog/BlogManagerImplTest.java

@@ -14,8 +14,6 @@ import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
-import org.briarproject.bramble.api.sync.Group;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.blog.Blog;
@@ -34,6 +32,7 @@ import static org.briarproject.bramble.api.identity.Author.Status.NONE;
 import static org.briarproject.bramble.api.identity.Author.Status.OURSELVES;
 import static org.briarproject.bramble.api.identity.Author.Status.VERIFIED;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_LENGTH;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
@@ -867,9 +866,7 @@ public class BlogManagerImplTest extends BriarTestCase {
 	}
 
 	private Blog createBlog(LocalAuthor localAuthor, boolean rssFeed) {
-		GroupId groupId = new GroupId(getRandomId());
-		Group group = new Group(groupId, CLIENT_ID, getRandomBytes(42));
-		return new Blog(group, localAuthor, rssFeed);
+		return new Blog(getGroup(CLIENT_ID), localAuthor, rssFeed);
 	}
 
 	private BdfList authorToBdfList(Author a) {

briar-core/src/test/java/org/briarproject/briar/blog/BlogPostValidatorTest.java

@@ -8,7 +8,6 @@ import org.briarproject.bramble.api.data.MetadataEncoder;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupFactory;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
@@ -25,6 +24,7 @@ import java.io.IOException;
 import java.security.GeneralSecurityException;
 
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
@@ -64,9 +64,8 @@ public class BlogPostValidatorTest extends BriarTestCase {
 	private final String body = getRandomString(42);
 
 	public BlogPostValidatorTest() {
-		GroupId groupId = new GroupId(getRandomId());
-		descriptor = getRandomBytes(42);
-		group = new Group(groupId, CLIENT_ID, descriptor);
+		group = getGroup(CLIENT_ID);
+		descriptor = group.getDescriptor();
 		author = getAuthor();
 		authorList = BdfList.of(
 				author.getFormatVersion(),

briar-core/src/test/java/org/briarproject/briar/client/MessageQueueManagerImplTest.java

@@ -19,7 +19,6 @@ import org.briarproject.bramble.api.sync.ValidationManager.MessageValidator;
 import org.briarproject.bramble.test.CaptureArgumentAction;
 import org.briarproject.bramble.test.TestUtils;
 import org.briarproject.bramble.util.ByteUtils;
-import org.briarproject.bramble.util.StringUtils;
 import org.briarproject.briar.api.client.MessageQueueManager.IncomingQueueMessageHook;
 import org.briarproject.briar.api.client.MessageQueueManager.QueueMessageValidator;
 import org.briarproject.briar.api.client.QueueMessage;
@@ -35,6 +34,8 @@ import org.junit.Test;
 import java.util.concurrent.atomic.AtomicReference;
 
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.briar.api.client.MessageQueueManager.QUEUE_STATE_KEY;
 import static org.briarproject.briar.api.client.QueueMessage.QUEUE_MESSAGE_HEADER_LENGTH;
 import static org.junit.Assert.assertEquals;
@@ -44,11 +45,9 @@ import static org.junit.Assert.fail;
 
 public class MessageQueueManagerImplTest extends BriarTestCase {
 
-	private final GroupId groupId = new GroupId(TestUtils.getRandomId());
-	private final ClientId clientId =
-			new ClientId(StringUtils.getRandomString(5));
-	private final byte[] descriptor = new byte[0];
-	private final Group group = new Group(groupId, clientId, descriptor);
+	private final ClientId clientId = getClientId();
+	private final Group group = getGroup(clientId);
+	private final GroupId groupId = group.getId();
 	private final long timestamp = System.currentTimeMillis();
 
 	@Test

briar-core/src/test/java/org/briarproject/briar/feed/FeedManagerImplTest.java

@@ -37,6 +37,7 @@ import javax.net.SocketFactory;
 
 import okhttp3.Dns;
 
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
@@ -60,12 +61,10 @@ public class FeedManagerImplTest extends BrambleMockTestCase {
 	private final Clock clock = context.mock(Clock.class);
 	private final Dns noDnsLookups = context.mock(Dns.class);
 
-	private final GroupId localGroupId = new GroupId(getRandomId());
-	private final Group localGroup =
-			new Group(localGroupId, CLIENT_ID, getRandomBytes(42));
-	private final GroupId blogGroupId = new GroupId(getRandomId());
-	private final Group blogGroup =
-			new Group(blogGroupId, BlogManager.CLIENT_ID, getRandomBytes(42));
+	private final Group localGroup = getGroup(CLIENT_ID);
+	private final GroupId localGroupId = localGroup.getId();
+	private final Group blogGroup = getGroup(BlogManager.CLIENT_ID);
+	private final GroupId blogGroupId = blogGroup.getId();
 	private final LocalAuthor localAuthor = getLocalAuthor();
 	private final Blog blog = new Blog(blogGroup, localAuthor, true);
 	private final Feed feed =

briar-core/src/test/java/org/briarproject/briar/introduction/IntroduceeManagerTest.java

@@ -19,7 +19,6 @@ import org.briarproject.bramble.api.identity.AuthorFactory;
 import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
@@ -40,6 +39,7 @@ import static org.briarproject.bramble.api.crypto.CryptoConstants.MAX_AGREEMENT_
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
@@ -79,6 +79,7 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_ACK;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_REQUEST;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_RESPONSE;
+import static org.briarproject.briar.api.introduction.IntroductionManager.CLIENT_ID;
 import static org.hamcrest.Matchers.array;
 import static org.hamcrest.Matchers.samePropertyValuesAs;
 import static org.junit.Assert.assertFalse;
@@ -145,11 +146,8 @@ public class IntroduceeManagerTest extends BriarTestCase {
 		introducee2 =
 				new Contact(contactId2, author2, localAuthorId, true, true);
 
-		ClientId clientId = IntroductionManagerImpl.CLIENT_ID;
-		localGroup1 = new Group(new GroupId(getRandomId()),
-				clientId, new byte[0]);
-		introductionGroup1 = new Group(new GroupId(getRandomId()),
-				clientId, new byte[0]);
+		localGroup1 = getGroup(CLIENT_ID);
+		introductionGroup1 = getGroup(CLIENT_ID);
 
 		sessionId = new SessionId(getRandomId());
 		localStateMessage = new Message(

briar-core/src/test/java/org/briarproject/briar/introduction/IntroducerManagerTest.java

@@ -12,9 +12,7 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
-import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.system.Clock;
@@ -27,6 +25,7 @@ import org.junit.Test;
 import java.security.SecureRandom;
 
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.briar.api.introduction.IntroducerProtocolState.AWAIT_RESPONSES;
@@ -50,6 +49,7 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.STAT
 import static org.briarproject.briar.api.introduction.IntroductionConstants.STORAGE_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_REQUEST;
+import static org.briarproject.briar.api.introduction.IntroductionManager.CLIENT_ID;
 import static org.junit.Assert.assertFalse;
 
 public class IntroducerManagerTest extends BriarTestCase {
@@ -93,12 +93,9 @@ public class IntroducerManagerTest extends BriarTestCase {
 		introducee2 =
 				new Contact(contactId2, author2, localAuthorId2, true, true);
 
-		localGroup0 = new Group(new GroupId(getRandomId()),
-				getClientId(), new byte[0]);
-		introductionGroup1 = new Group(new GroupId(getRandomId()),
-				getClientId(), new byte[0]);
-		introductionGroup2 = new Group(new GroupId(getRandomId()),
-				getClientId(), new byte[0]);
+		localGroup0 = getGroup(CLIENT_ID);
+		introductionGroup1 = getGroup(CLIENT_ID);
+		introductionGroup2 = getGroup(CLIENT_ID);
 
 		context.assertIsSatisfied();
 	}
@@ -179,8 +176,4 @@ public class IntroducerManagerTest extends BriarTestCase {
 		assertFalse(txn.isCommitted());
 	}
 
-	private ClientId getClientId() {
-		return IntroductionManagerImpl.CLIENT_ID;
-	}
-
 }

briar-core/src/test/java/org/briarproject/briar/introduction/IntroductionIntegrationTest.java

@@ -19,7 +19,6 @@ import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
 import org.briarproject.bramble.api.sync.Group;
@@ -54,6 +53,7 @@ import javax.inject.Inject;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
 import static org.briarproject.bramble.test.TestPluginConfigModule.TRANSPORT_ID;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.briarproject.briar.api.client.MessageQueueManager.QUEUE_STATE_KEY;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.ALICE_MAC_KEY_LABEL;
@@ -372,7 +372,7 @@ public class IntroductionIntegrationTest
 		TransportProperties tp = new TransportProperties(
 				Collections.singletonMap("key", "value"));
 		c0.getTransportPropertyManager()
-				.mergeLocalProperties(new TransportId("fake"), tp);
+				.mergeLocalProperties(getTransportId(), tp);
 		sync0To1(1, true);
 
 		// sync second response

briar-core/src/test/java/org/briarproject/briar/introduction/IntroductionManagerImplTest.java

@@ -13,9 +13,7 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
-import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.MessageStatus;
@@ -33,9 +31,9 @@ import java.util.Map;
 
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
-import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.GROUP_ID_1;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.GROUP_ID_2;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.ROLE;
@@ -44,6 +42,7 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.SESS
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_REQUEST;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_RESPONSE;
+import static org.briarproject.briar.api.introduction.IntroductionManager.CLIENT_ID;
 import static org.junit.Assert.assertFalse;
 
 public class IntroductionManagerImplTest extends BriarTestCase {
@@ -79,11 +78,8 @@ public class IntroductionManagerImplTest extends BriarTestCase {
 		introducee2 =
 				new Contact(contactId2, author2, localAuthorId2, true, true);
 
-		ClientId clientId = new ClientId(getRandomString(5));
-		introductionGroup1 = new Group(new GroupId(getRandomId()),
-				clientId, new byte[0]);
-		introductionGroup2 = new Group(new GroupId(getRandomId()),
-				clientId, new byte[0]);
+		introductionGroup1 = getGroup(CLIENT_ID);
+		introductionGroup2 = getGroup(CLIENT_ID);
 
 		message1 = new Message(
 				new MessageId(getRandomId()),

briar-core/src/test/java/org/briarproject/briar/introduction/IntroductionValidatorTest.java

@@ -8,9 +8,7 @@ import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.data.MetadataEncoder;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.system.Clock;
@@ -27,6 +25,8 @@ import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATUR
 import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MAX_PROPERTY_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_LENGTH;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
@@ -61,11 +61,7 @@ public class IntroductionValidatorTest extends BriarTestCase {
 	private final Clock clock = new SystemClock();
 
 	public IntroductionValidatorTest() {
-		GroupId groupId = new GroupId(getRandomId());
-		ClientId clientId = new ClientId(getRandomString(5));
-		byte[] descriptor = getRandomBytes(12);
-		group = new Group(groupId, clientId, descriptor);
-
+		group = getGroup(getClientId());
 		MessageId messageId = new MessageId(getRandomId());
 		long timestamp = System.currentTimeMillis();
 		byte[] raw = getRandomBytes(123);

briar-core/src/test/java/org/briarproject/briar/introduction/MessageSenderTest.java

@@ -10,12 +10,8 @@ import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.db.Transaction;
-import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.test.TestUtils;
-import org.briarproject.bramble.util.StringUtils;
 import org.briarproject.briar.api.client.MessageQueueManager;
 import org.briarproject.briar.api.client.SessionId;
 import org.briarproject.briar.test.BriarTestCase;
@@ -24,6 +20,10 @@ import org.jmock.Mockery;
 import org.junit.Test;
 
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.GROUP_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.SESSION_ID;
@@ -59,13 +59,10 @@ public class MessageSenderTest extends BriarTestCase {
 	@Test
 	public void testSendMessage() throws DbException, FormatException {
 		Transaction txn = new Transaction(null, false);
-		Group privateGroup =
-				new Group(new GroupId(TestUtils.getRandomId()),
-						new ClientId(StringUtils.getRandomString(5)),
-						new byte[0]);
-		SessionId sessionId = new SessionId(TestUtils.getRandomId());
-		byte[] mac = TestUtils.getRandomBytes(42);
-		byte[] sig = TestUtils.getRandomBytes(MAX_SIGNATURE_LENGTH);
+		Group privateGroup = getGroup(getClientId());
+		SessionId sessionId = new SessionId(getRandomId());
+		byte[] mac = getRandomBytes(42);
+		byte[] sig = getRandomBytes(MAX_SIGNATURE_LENGTH);
 		long time = 42L;
 		BdfDictionary msg = BdfDictionary.of(
 				new BdfEntry(TYPE, TYPE_ACK),
@@ -76,7 +73,7 @@ public class MessageSenderTest extends BriarTestCase {
 		);
 		BdfList bodyList =
 				BdfList.of(TYPE_ACK, sessionId.getBytes(), mac, sig);
-		byte[] body = TestUtils.getRandomBytes(8);
+		byte[] body = getRandomBytes(8);
 		Metadata metadata = new Metadata();
 
 		context.checking(new Expectations() {{

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/AbstractProtocolEngineTest.java

@@ -25,6 +25,7 @@ import org.jmock.Expectations;
 
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
@@ -63,9 +64,8 @@ public abstract class AbstractProtocolEngineTest extends BrambleMockTestCase {
 
 	protected final Transaction txn = new Transaction(null, false);
 	protected final GroupId contactGroupId = new GroupId(getRandomId());
-	protected final GroupId privateGroupId = new GroupId(getRandomId());
-	protected final Group privateGroupGroup =
-			new Group(privateGroupId, CLIENT_ID, getRandomBytes(123));
+	protected final Group privateGroupGroup = getGroup(CLIENT_ID);
+	protected final GroupId privateGroupId = privateGroupGroup.getId();
 	protected final Author author = getAuthor();
 	protected final PrivateGroup privateGroup =
 			new PrivateGroup(privateGroupGroup,

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/GroupInvitationManagerImplTest.java

@@ -854,10 +854,8 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 		Collection<Contact> contacts =
 				Arrays.asList(contact, contact2, contact3);
 
-		Group contactGroup2 = new Group(new GroupId(getRandomId()),
-				CLIENT_ID, getRandomBytes(5));
-		Group contactGroup3 = new Group(new GroupId(getRandomId()),
-				CLIENT_ID, getRandomBytes(5));
+		Group contactGroup2 = getGroup(CLIENT_ID);
+		Group contactGroup3 = getGroup(CLIENT_ID);
 
 		MessageId storageId2 = new MessageId(getRandomId());
 		MessageId storageId3 = new MessageId(getRandomId());

briar-core/src/test/java/org/briarproject/briar/sharing/BlogSharingManagerImplTest.java

@@ -15,7 +15,6 @@ import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.sync.Group;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.test.BrambleMockTestCase;
@@ -226,8 +225,7 @@ public class BlogSharingManagerImplTest extends BrambleMockTestCase {
 	private void expectPreShareShareable(Transaction txn, Contact contact,
 			Blog blog, Map<MessageId, BdfDictionary> sessions)
 			throws Exception {
-		Group contactGroup = new Group(new GroupId(getRandomId()), CLIENT_ID,
-				getRandomBytes(42));
+		Group contactGroup = getGroup(CLIENT_ID);
 		BdfDictionary sessionDict = new BdfDictionary();
 		Message message = new Message(new MessageId(getRandomId()),
 				contactGroup.getId(), 42L, getRandomBytes(1337));