diff --git a/src/RdfWriterFactory.php b/src/RdfWriterFactory.php
index 9c6459e..b0490e5 100644
--- a/src/RdfWriterFactory.php
+++ b/src/RdfWriterFactory.php
@@ -1,172 +1,173 @@
 <?php
 
 namespace Wikimedia\Purtle;
 
 use InvalidArgumentException;
 
 /**
  * @since 0.5
  *
  * @license GPL-2.0-or-later
  * @author Daniel Kinzler
  */
 class RdfWriterFactory {
 
 	/**
 	 * Returns a list of canonical format names.
 	 * These names for internal use with getMimeTypes() and getFileExtension(),
 	 * they are not themselves MIME types or file extensions.
 	 *
 	 * @return string[]
 	 */
 	public function getSupportedFormats() {
 		return [ 'n3', 'turtle', 'ntriples', 'rdfxml', 'jsonld' ];
 	}
 
 	/**
 	 * Returns a list of mime types that correspond to the format.
 	 *
 	 * @param string $format a format name, as returned by getSupportedFormats() or getFormatName().
 	 *
 	 * @throws InvalidArgumentException if $format is not a cononical format name
 	 * @return string[]
 	 */
 	public function getMimeTypes( $format ) {
 		// NOTE: Maintaining mime types and file extensions in the RdfWriter implementations
 		// is tempting, but means we have to load all these classes to find the right
 		// one for a requested name. Better avoid that overhead when serving lots of
 		// HTTP requests.
 
 		switch ( strtolower( $format ) ) {
 			case 'n3':
 				return [ 'text/n3', 'text/rdf+n3' ];
 
 			case 'turtle':
 				return [ 'text/turtle', 'application/x-turtle' ];
 
 			case 'ntriples':
 				return [ 'application/n-triples', 'text/n-triples', 'text/plain' ];
 
 			case 'rdfxml':
 				return [ 'application/rdf+xml', 'application/xml', 'text/xml' ];
 
 			case 'jsonld':
 				return [ 'application/ld+json', 'application/json' ];
 
 			default:
 				throw new InvalidArgumentException( 'Bad format: ' . $format );
 		}
 	}
 
 	/**
 	 * Returns a file extension that correspond to the format.
 	 *
 	 * @param string $format a format name, as returned by getSupportedFormats() or getFormatName().
 	 *
 	 * @throws InvalidArgumentException if $format is not a cononical format name
 	 * @return string
 	 */
 	public function getFileExtension( $format ) {
 		switch ( strtolower( $format ) ) {
 			case 'n3':
 				return 'n3';
 
 			case 'turtle':
 				return 'ttl';
 
 			case 'ntriples':
 				return 'nt';
 
 			case 'rdfxml':
 				return 'rdf';
 
 			case 'jsonld':
 				return 'jsonld';
 
 			default:
 				throw new InvalidArgumentException( 'Bad format: ' . $format );
 		}
 	}
 
 	/**
 	 * Returns an RdfWriter for the given format name.
 	 *
 	 * @param string $format a format name, as returned by getSupportedFormats() or getFormatName().
+	 * @param BNodeLabeler|null $labeler Optional labeler
 	 *
-	 * @throws InvalidArgumentException if $format is not a cononical format name
+ 	 * @throws InvalidArgumentException if $format is not a canonical format name
 	 * @return RdfWriter the format object, or null if not found.
 	 */
-	public function getWriter( $format ) {
+	public function getWriter( $format, BNodeLabeler $labeler = null ) {
 		switch ( strtolower( $format ) ) {
 			case 'n3':
 				// falls through to turtle
 
 			case 'turtle':
-				return new TurtleRdfWriter();
+				return new TurtleRdfWriter( RdfWriterBase::DOCUMENT_ROLE, $labeler );
 
 			case 'ntriples':
-				return new NTriplesRdfWriter();
+				return new NTriplesRdfWriter( RdfWriterBase::DOCUMENT_ROLE, $labeler );
 
 			case 'rdfxml':
-				return new XmlRdfWriter();
+				return new XmlRdfWriter( RdfWriterBase::DOCUMENT_ROLE, $labeler );
 
 			case 'jsonld':
-				return new JsonLdRdfWriter();
+				return new JsonLdRdfWriter( RdfWriterBase::DOCUMENT_ROLE, $labeler );
 
 			default:
 				throw new InvalidArgumentException( 'Bad format: ' . $format );
 		}
 	}
 
 	/**
 	 * Returns the canonical format name for $format. $format may be a file extension,
 	 * a mime type, or a common or canonical name of the format.
 	 *
 	 * If no format is found for $format, this method returns false.
 	 *
 	 * @param string $format the name (file extension, mime type) of the desired format.
 	 *
 	 * @return string|false the canonical format name
 	 */
 	public function getFormatName( $format ) {
 		switch ( strtolower( $format ) ) {
 			case 'n3':
 			case 'text/n3':
 			case 'text/rdf+n3':
 				return 'n3';
 
 			case 'ttl':
 			case 'turtle':
 			case 'text/turtle':
 			case 'application/x-turtle':
 				return 'turtle';
 
 			case 'nt':
 			case 'ntriples':
 			case 'n-triples':
 			case 'text/plain':
 			case 'text/n-triples':
 			case 'application/ntriples':
 			case 'application/n-triples':
 				return 'ntriples';
 
 			case 'xml':
 			case 'rdf':
 			case 'rdfxml':
 			case 'application/rdf+xml':
 			case 'application/xml':
 			case 'text/xml':
 				return 'rdfxml';
 
 			case 'json':
 			case 'jsonld':
 			case 'application/ld+json':
 			case 'application/json':
 				return 'jsonld';
 
 			default:
 				return false;
 		}
 	}
 
 }
diff --git a/tests/phpunit/JsonLdRdfWriterTest.php b/tests/phpunit/JsonLdRdfWriterTest.php
index d9bd83c..9746349 100644
--- a/tests/phpunit/JsonLdRdfWriterTest.php
+++ b/tests/phpunit/JsonLdRdfWriterTest.php
@@ -1,47 +1,47 @@
 <?php
 
 namespace Wikimedia\Purtle\Tests;
 
 use Wikimedia\Purtle\RdfWriter;
 use Wikimedia\Purtle\JsonLdRdfWriter;
 
 /**
- * @covers Wikimedia\Purtle\JsonLdRdfWriter
- * @covers Wikimedia\Purtle\RdfWriterBase
+ * @covers \Wikimedia\Purtle\JsonLdRdfWriter
+ * @covers \Wikimedia\Purtle\RdfWriterBase
  *
  * @group Purtle
  * @group RdfWriter
  *
  * @license GPL-2.0-or-later
  * @author C. Scott Ananian
  */
 class JsonLdRdfWriterTest extends RdfWriterTestBase {
 
 	/**
 	 * @return string
 	 */
 	protected function getFileSuffix() {
 		return 'jsonld';
 	}
 
 	/**
 	 * @return RdfWriter
 	 */
 	protected function newWriter() {
 		return new JsonLdRdfWriter();
 	}
 
 	public function testEncode() {
 		$writer = new JsonLdRdfWriter();
 		$this->assertEquals( $writer->encode( 'foo{bar}bat', 0 ), '"foo{bar}bat"' );
 		$this->assertEquals( $writer->encode( [], 0 ), '' );
 		$this->assertEquals( $writer->encode( [
 			'@id' => 'foo'
 		], 0 ), '    "@id": "foo"' );
 		$this->assertEquals(
 			$writer->encode( [ 1, 2, 3 ], 0 ),
 			"    1,\n    2,\n    3"
 		);
 	}
 
 }
diff --git a/tests/phpunit/RdfWriterTestBase.php b/tests/phpunit/RdfWriterTestBase.php
index 7393f19..b3dae4b 100644
--- a/tests/phpunit/RdfWriterTestBase.php
+++ b/tests/phpunit/RdfWriterTestBase.php
@@ -1,454 +1,474 @@
 <?php
 
 namespace Wikimedia\Purtle\Tests;
 
+use Wikimedia\Purtle\BNodeLabeler;
 use Wikimedia\Purtle\RdfWriter;
+use Wikimedia\Purtle\RdfWriterFactory;
 
 /**
  * Base class for tests for RdfWriter implementations.
  * Provides a common test suite for all implementations.
  *
  * @license GPL-2.0-or-later
  * @author Daniel Kinzler
  * @author Thiemo Kreuz
  */
 abstract class RdfWriterTestBase extends \PHPUnit\Framework\TestCase {
 
 	abstract protected function getFileSuffix();
 
 	/**
 	 * @return RdfWriter
 	 */
 	abstract protected function newWriter();
 
 	/**
 	 * Returns true iff lines are independent in this writer format, and
 	 * so lines should be sorted before comparison with expected in
 	 * assertNTriplesEquals().
 	 * @return bool
 	 */
 	protected function sortLines() {
 		return false;
 	}
 
 	public function testGetMimeType() {
 		$mimeType = $this->newWriter()->getMimeType();
 		$this->assertInternalType( 'string', $mimeType );
 		$this->assertRegExp( '/^\w+\/[\w-]+(\+(xml|json))?(; charset=UTF-8)?$/', $mimeType );
 	}
 
 	public function testTriples() {
 		$writer = $this->newWriter();
 
 		$writer->prefix( 'acme', 'http://acme.test/' );
 		$writer->start();
 
 		$writer->about( 'http://foobar.test/Bananas' )
 			->say( 'a' )->is( 'http://foobar.test/Fruit' ); // shorthand name "a"
 
 		$writer->about( 'acme', 'Nuts' )
 			->say( 'acme', 'weight' )->value( '5.5', 'xsd', 'decimal' );
 
 		// redundant about( 'acme', 'Nuts' )
 		$writer->about( 'acme', 'Nuts' )
 			->say( 'acme', 'color' )->value( 'brown' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'Triples', $rdf );
 	}
 
 	public function testPredicates() {
 		$writer = $this->newWriter();
 
 		$writer->prefix( '', 'http://acme.test/' ); // empty prefix
 		$writer->start();
 
 		$writer->about( 'http://foobar.test/Bananas' )
 			->a( 'http://foobar.test/Fruit' ) // shorthand function a()
 			->say( '', 'name' ) // empty prefix
 				->text( 'Banana' )
 			->say( '', 'name' ) // redundant say( '', 'name' )
 				->text( 'Banane', 'de' );
 
 		$writer->about( 'http://foobar.test/Apples' )
 			->say( '', 'name' ) // subsequent call to say( '', 'name' ) for a different subject
 				->text( 'Apple' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'Predicates', $rdf );
 	}
 
 	public function testPredicates_drain() {
 		$writer = $this->newWriter();
 
 		$writer->prefix( '', 'http://acme.test/' ); // empty prefix
 		$writer->start();
 
 		$writer->about( 'http://foobar.test/Bananas' )
 			->a( 'http://foobar.test/Fruit' ) // shorthand function a()
 			->say( '', 'name' ) // empty prefix
 			->text( 'Banana' )
 			->say( '', 'name' ) // redundant say( '', 'name' )
 			->text( 'Banane', 'de' );
 
 		$rdf1 = $writer->drain();
 		$this->assertNotEmpty( $rdf1 );
 
 		$writer->about( 'http://foobar.test/Apples' )
 			->say( '', 'name' ) // subsequent call to say( '', 'name' ) for a different subject
 			->text( 'Apple' );
 		$writer->finish();
 
 		$rdf2 = $writer->drain();
 		$this->assertNotEmpty( $rdf2 );
 
 		$this->assertOutputLines( 'Predicates', $rdf1 . $rdf2 );
 	}
 
 	public function testPredicates_sub() {
 		$writer = $this->newWriter();
 
 		$writer->prefix( '', 'http://acme.test/' ); // empty prefix
 		$writer->start();
 
 		$sub = $writer->sub();
 
 		// output of the sub writer will appear after the output of the main writer.
 		$sub->about( 'http://foobar.test/Apples' )
 			->say( '', 'name' ) // subsequent call to say( '', 'name' ) for a different subject
 			->text( 'Apple' );
 
 		$writer->about( 'http://foobar.test/Bananas' )
 			->a( 'http://foobar.test/Fruit' ) // shorthand function a()
 			->say( '', 'name' ) // empty prefix
 			->text( 'Banana' )
 			->say( '', 'name' ) // redundant say( '', 'name' )
 			->text( 'Banane', 'de' );
 
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'Predicates', $rdf );
 	}
 
 	public function testPredicates_sub_drain() {
 		$writer = $this->newWriter();
 
 		$writer->prefix( '', 'http://acme.test/' ); // empty prefix
 		$writer->start();
 
 		$sub = $writer->sub();
 
 		$writer->about( 'http://foobar.test/Bananas' )
 			->a( 'http://foobar.test/Fruit' ) // shorthand function a()
 			->say( '', 'name' ) // empty prefix
 			->text( 'Banana' )
 			->say( '', 'name' ) // redundant say( '', 'name' )
 			->text( 'Banane', 'de' );
 
 		$rdf1 = $writer->drain();
 		$this->assertNotEmpty( $rdf1 );
 
 		// sub-writer should still be usable after drain()
 		$sub->about( 'http://foobar.test/Apples' )
 			->say( '', 'name' ) // subsequent call to say( '', 'name' ) for a different subject
 			->text( 'Apple' );
 
 		$writer->finish();
 
 		$rdf2 = $writer->drain();
 		$this->assertNotEmpty( $rdf2 );
 
 		$this->assertOutputLines( 'Predicates', $rdf1 . $rdf2 );
 	}
 
 	public function testValues() {
 		$writer = $this->newWriter();
 
 		$writer->prefix( 'acme', 'http://acme.test/' );
 		$writer->start();
 
 		$writer->about( 'http://foobar.test/Bananas' )
 			->say( 'acme', 'multi' )
 				->value( 'A' )
 				->value( 'B' )
 				->value( 'C' )
 			->say( 'acme', 'type' )
 				->value( 'foo', 'acme', 'thing' )
 				->value( '-5', 'xsd', 'integer' )
 				->value( '-5', 'xsd', 'decimal' )
 				->value( '-5', 'xsd', 'double' )
 				->value( 'true', 'xsd', 'boolean' )
 				->value( 'false', 'xsd', 'boolean' )
 			->say( 'acme', 'autotype' )
 				->value( -5 )
 				->value( 3.14 )
 				->value( true )
 				->value( false )
 			->say( 'acme', 'no-autotype' )
 				->value( -5, 'xsd', 'decimal' )
 				->value( 3.14, 'xsd', 'string' )
 				->value( true, 'xsd', 'string' )
 				->value( false, 'xsd', 'string' )
 			->say( 'acme', 'shorthand' )->value( 'foo' )
 			->say( 'acme', 'typed-shorthand' )->value( 'foo', 'acme', 'thing' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'Values', $rdf );
 	}
 
 	public function testResources() {
 		$writer = $this->newWriter();
 
 		$writer->prefix( 'acme', 'http://acme.test/' );
 		$writer->start();
 
 		$writer->about( 'acme', 'Bongos' )
 			->say( 'acme', 'sounds' )
 				->is( 'acme', 'Bing' )
 				->is( 'http://foobar.test/sound/Bang' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'Resources', $rdf );
 	}
 
 	public function testTexts() {
 		$writer = $this->newWriter();
 
 		$writer->prefix( 'acme', 'http://acme.test/' );
 		$writer->start();
 
 		$writer->about( 'acme', 'Bongos' )
 			->say( 'acme', 'sounds' )
 				->text( 'Bom', 'de' )
 				->text( 'Bam', 'en' )
 				->text( 'Como estas', 'es-419' )
 				->text( 'What?', 'bad tag' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'Texts', $rdf );
 	}
 
 	public function testNumbers() {
 		$writer = $this->newWriter();
 
 		$writer->prefix( 'acme', 'http://acme.test/' );
 		$writer->start();
 
 		$writer->about( 'acme', 'Bongos' )
 			->say( 'acme', 'stock' )->value( 5, 'xsd', 'integer' )
 				->value( 7 )
 		->about( 'acme', 'Tablas' )
 			->say( 'acme', 'stock' )->value( 6 );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'Numbers', $rdf );
 	}
 
 	public function testEricMiller() {
 		// example taken from http://www.w3.org/2007/02/turtle/primer/
 
 		$writer = $this->newWriter();
 
 		$writer->prefix( 'contact', 'http://www.w3.org/2000/10/swap/pim/contact#' );
 		$writer->start();
 
 		$writer->about( 'http://www.w3.org/People/EM/contact#me' )
 			->say( 'rdf', 'type' )->is( 'contact', 'Person' )
 			->say( 'contact', 'fullName' )->text( 'Eric Miller' )
 			->say( 'contact', 'mailbox' )->is( 'mailto:em@w3.org' )
 			->say( 'contact', 'personalTitle' )->text( 'Dr.' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'EricMiller', $rdf );
 	}
 
 	public function testLabeledBlankNode() {
 		// example taken from http://www.w3.org/2007/02/turtle/primer/
 
 		$writer = $this->newWriter();
 
 		$writer->prefix( 'exterms', 'http://www.example.org/terms/' );
 		$writer->prefix( 'exstaff', 'http://www.example.org/staffid/' );
 		$writer->start();
 
 		$writer->about( 'exstaff', '85740' )
 			->say( 'exterms', 'address' )->is( '_', $label = $writer->blank( 'johnaddress' ) )
 		->about( '_', $label )
 			->say( 'exterms', 'street' )->text( '1501 Grant Avenue' )
 			->say( 'exterms', 'city' )->text( 'Bedfort' )
 			->say( 'exterms', 'state' )->text( 'Massachusetts' )
 			->say( 'exterms', 'postalCode' )->text( '01730' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'LabeledBlankNode', $rdf );
 	}
 
 	public function testNumberedBlankNodes() {
 		// example taken from http://www.w3.org/2007/02/turtle/primer/
 
 		$writer = $this->newWriter();
 
 		$writer->prefix( 'exterms', 'http://www.example.org/terms/' );
 		$writer->prefix( 'exstaff', 'http://www.example.org/staffid/' );
 		$writer->prefix( 'ex', 'http://example.org/packages/vocab#' );
 		$writer->start();
 
 		$writer->about( 'exstaff', 'Sue' )
 			->say( 'exterms', 'publication' )->is( '_', $label1 = $writer->blank() );
 		$writer->about( '_', $label1 )
 			->say( 'exterms', 'title' )->text( 'Antology of Time' );
 
 		$writer->about( 'exstaff', 'Jack' )
 			->say( 'exterms', 'publication' )->is( '_', $label2 = $writer->blank() );
 		$writer->about( '_', $label2 )
 			->say( 'exterms', 'title' )->text( 'Anthony of Time' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'NumberedBlankNode', $rdf );
 	}
 
 	public function testQuotesAndSpecials() {
 		$writer = $this->newWriter();
 		$writer->prefix( 'exterms', 'http://www.example.org/terms/' );
 		$writer->start();
 
 		$writer->about( 'exterms', 'Duck' )->say( 'exterms', 'says' )
 			->text( 'Duck says: "Quack!"' );
 		$writer->about( 'exterms', 'Cow' )->say( 'exterms', 'says' )
 			->text( "Cow says:\n\r 'Moo! \\Moo!'" );
 		$writer->about( 'exterms', 'Bear' )->say( 'exterms', 'says' )
 			->text( 'Bear says: Превед!' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'TextWithSpecialChars', $rdf );
 	}
 
 	public function testDumpHeader() {
 		$writer = $this->newWriter();
 		$writer->prefix( 'wikibase', 'http://wikiba.se/ontology-beta#' );
 		$writer->prefix( 'schema', 'http://schema.org/' );
 		$writer->prefix( 'owl', 'http://www.w3.org/2002/07/owl#' );
 		$writer->prefix( 'cc', 'http://creativecommons.org/ns#' );
 		$writer->start();
 		$writer->about( 'wikibase', 'Dump' )
 			->a( 'schema', 'Dataset' )
 			->a( 'owl', 'Ontology' )
 			->say( 'cc', 'license' )->is( 'http://creativecommons.org/publicdomain/zero/1.0/' )
 			->say( 'schema', 'softwareVersion' )->value( '0.1.0' )
 			->say( 'schema', 'dateModified' )->value( '2017-09-19T22:53:13-04:00', 'xsd', 'dateTime' )
 			->say( 'owl', 'imports' )->is( 'http://wikiba.se/ontology-1.0.owl' );
 		$writer->finish();
 
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'DumpHeader', $rdf );
 	}
 
 	public function testAlternatingValues() {
 		$writer = $this->newWriter();
 		$writer->prefix( 'wikibase', 'http://wikiba.se/ontology-beta#' );
 		$writer->prefix( 'owl', 'http://www.w3.org/2002/07/owl#' );
 		$writer->start();
 		$writer->about( 'wikibase', 'Dump' )
 			->say( 'owl', 'foo' )->is( 'owl', 'A' )
 			->say( 'owl', 'bar' )->value( '5', 'xsd', 'decimal' )
 			->say( 'owl', 'foo' )->is( 'owl', 'B' )
 			->say( 'owl', 'bar' )->value( '6', 'xsd', 'decimal' )
 			->say( 'owl', 'foo' )->is( 'owl', 'C' )
 			->say( 'owl', 'bar' )->value( '7', 'xsd', 'decimal' );
 		$writer->finish();
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'AlternatingValues', $rdf );
 	}
 
 	public function testTypeConflict() {
 		$writer = $this->newWriter();
 		$writer->prefix( 'ex', 'http://example.com/' );
 		$writer->start();
 		$writer->about( 'ex', 'A' )
 			->say( 'ex', 'foo' )->is( 'ex', 'Node' )
 			->say( 'ex', 'foo' )->value( '5', 'xsd', 'decimal' )
 			->say( 'ex', 'foo' )->value( 'string' )
 			->say( 'ex', 'bar' )->value( 'string' )
 			->say( 'ex', 'bar' )->value( '5', 'xsd', 'decimal' )
 			->say( 'ex', 'bat' )->value( 'string' );
 		// A blank node is used in clients to indicate "any value"
 		$writer->about( 'ex', 'B' )
 			->say( 'ex', 'bat' )->is( '_', $writer->blank() );
 
 		$writer->finish();
 		$rdf = $writer->drain();
 		$this->assertOutputLines( 'TypeConflict', $rdf );
 	}
 
+	/**
+	 * @return RdfWriter
+	 */
+	protected function newWriterFactory( BNodeLabeler $labeler = null) {
+		$factory = new RdfWriterFactory();
+		return $factory->getWriter( $factory->getFormatName( $this->getFileSuffix() ), $labeler );
+	}
+
+	public function testSetLabeler() {
+		$writer = $this->newWriterFactory();
+		$bnode = $writer->blank();
+		$this->assertEquals( 'genid1', $bnode );
+
+		$writer = $this->newWriterFactory( new BNodeLabeler( 'testme2-', 10 ) );
+		$bnode = $writer->blank();
+		$this->assertEquals( 'testme2-10', $bnode );
+	}
+
 	/**
 	 * @param string $datasetName
 	 * @param string[]|string $actual
 	 */
 	private function assertOutputLines( $datasetName, $actual ) {
 		$path = __DIR__ . '/../data/' . $datasetName . '.' . $this->getFileSuffix();
 
 		$this->assertNTriplesEquals(
 			file_get_contents( $path ),
 			$actual,
 			"Result mismatches data in $path"
 		);
 	}
 
 	/**
 	 * @param string[]|string $nTriples
 	 *
 	 * @return string[] Sorted alphabetically.
 	 */
 	protected function normalizeNTriples( $nTriples ) {
 		if ( is_string( $nTriples ) ) {
 			// Trim and ignore newlines at the end of the file only.
 			$nTriples = explode( "\n", rtrim( $nTriples, "\n" ) );
 		}
 
 		if ( $this->sortLines() ) {
 			sort( $nTriples );
 		}
 
 		return $nTriples;
 	}
 
 	/**
 	 * @param string[]|string $expected
 	 * @param string[]|string $actual
 	 * @param string $message
 	 */
 	protected function assertNTriplesEquals( $expected, $actual, $message = '' ) {
 		$expected = $this->normalizeNTriples( $expected );
 		$actual = $this->normalizeNTriples( $actual );
 
 		if ( $this->sortLines() ) {
 			// Comparing $expected and $actual directly would show triples that are present in both but
 			// shifted in position. That makes the output hard to read. Calculating the $missing and
 			// $extra sets helps.
 			$extra = array_diff( $actual, $expected );
 			$missing = array_diff( $expected, $actual );
 
 			// Cute: $missing and $extra can be equal only if they are empty. Comparing them here
 			// directly looks a bit odd in code, but produces meaningful output, especially if the input
 			// was sorted.
 			$this->assertEquals( $missing, $extra, $message );
 		} else {
 			$this->assertEquals( $expected, $actual, $message );
 		}
 	}
 
 	// FIXME: test non-ascii literals!
 	// FIXME: test uerl-encoding
 	// FIXME: test IRIs!
 }
diff --git a/tests/phpunit/TurtleRdfWriterTest.php b/tests/phpunit/TurtleRdfWriterTest.php
index 3eab9ac..2444ead 100644
--- a/tests/phpunit/TurtleRdfWriterTest.php
+++ b/tests/phpunit/TurtleRdfWriterTest.php
@@ -1,50 +1,50 @@
 <?php
 
 namespace Wikimedia\Purtle\Tests;
 
 use Wikimedia\Purtle\RdfWriter;
 use Wikimedia\Purtle\TurtleRdfWriter;
 
 /**
- * @covers Wikimedia\Purtle\TurtleRdfWriter
- * @covers Wikimedia\Purtle\N3RdfWriterBase
- * @covers Wikimedia\Purtle\RdfWriterBase
+ * @covers \Wikimedia\Purtle\TurtleRdfWriter
+ * @covers \Wikimedia\Purtle\N3RdfWriterBase
+ * @covers \Wikimedia\Purtle\RdfWriterBase
  *
- * @uses Wikimedia\Purtle\BNodeLabeler
- * @uses Wikimedia\Purtle\N3Quoter
+ * @uses \Wikimedia\Purtle\BNodeLabeler
+ * @uses \Wikimedia\Purtle\N3Quoter
  *
  * @group Purtle
  * @group RdfWriter
  *
  * @license GPL-2.0-or-later
  * @author Daniel Kinzler
  * @author Thiemo Kreuz
  */
 class TurtleRdfWriterTest extends RdfWriterTestBase {
 
 	protected function getFileSuffix() {
 		return 'ttl';
 	}
 
 	/**
 	 * @return bool
 	 */
 	protected function sortLines() {
 		return true;
 	}
 
 	/**
 	 * @return RdfWriter
 	 */
 	protected function newWriter() {
 		return new TurtleRdfWriter();
 	}
 
 	public function testTrustIRIs() {
 		$writer = new TurtleRdfWriter();
 		$this->assertTrue( $writer->getTrustIRIs(), 'initialy enabled' );
 		$writer->setTrustIRIs( false );
 		$this->assertFalse( $writer->getTrustIRIs(), 'disabled' );
 	}
 
 }
diff --git a/tests/phpunit/XmlRdfWriterTest.php b/tests/phpunit/XmlRdfWriterTest.php
index ae46869..8f0aead 100644
--- a/tests/phpunit/XmlRdfWriterTest.php
+++ b/tests/phpunit/XmlRdfWriterTest.php
@@ -1,33 +1,33 @@
 <?php
 
 namespace Wikimedia\Purtle\Tests;
 
 use Wikimedia\Purtle\XmlRdfWriter;
 use Wikimedia\Purtle\RdfWriter;
 
 /**
- * @covers Wikimedia\Purtle\XmlRdfWriter
- * @covers Wikimedia\Purtle\RdfWriterBase
+ * @covers \Wikimedia\Purtle\XmlRdfWriter
+ * @covers \Wikimedia\Purtle\RdfWriterBase
  *
- * @uses Wikimedia\Purtle\BNodeLabeler
+ * @uses \Wikimedia\Purtle\BNodeLabeler
  *
  * @group Purtle
  * @group RdfWriter
  *
  * @license GPL-2.0-or-later
  * @author Daniel Kinzler
  */
 class XmlRdfWriterTest extends RdfWriterTestBase {
 
 	protected function getFileSuffix() {
 		return 'rdf';
 	}
 
 	/**
 	 * @return RdfWriter
 	 */
 	protected function newWriter() {
 		return new XmlRdfWriter();
 	}
 
 }