Merge pull request #399

.travis.yml

@@ -5,10 +5,6 @@ sudo: false
 services:
   - mongodb
 
-env:
-  global:
-    - DRIVER_VERSION=stable SERVER_VERSION=3.4
-
 addons:
   apt:
     packages: &common_packages
@@ -18,7 +14,7 @@ matrix:
   fast_finish: true
   include:
     - php: 5.5
-      env: &common_env DRIVER_VERSION=stable SERVER_VERSION=3.4
+      env: &common_env DRIVER_VERSION=1.3.0RC1 SERVER_VERSION=3.4
       addons: &common_addons
         apt: 
           sources: [ mongodb-3.4-precise ]
@@ -36,25 +32,25 @@ matrix:
       env: *common_env
       addons: *common_addons
     - php: 7.0
-      env: DRIVER_VERSION=1.2.0 SERVER_VERSION=2.4
+      env: DRIVER_VERSION=1.3.0RC1 SERVER_VERSION=2.4
       addons:
         apt:
           sources: [ mongodb-upstart ]
           packages: [ mongodb-10gen, *common_packages ]
     - php: 7.0
-      env: DRIVER_VERSION=1.2.0 SERVER_VERSION=2.6
+      env: DRIVER_VERSION=1.3.0RC1 SERVER_VERSION=2.6
       addons:
         apt:
           sources: [ mongodb-upstart ]
           packages: [ mongodb-org, *common_packages ]
     - php: 7.0
-      env: DRIVER_VERSION=1.2.0 SERVER_VERSION=3.0
+      env: DRIVER_VERSION=1.3.0RC1 SERVER_VERSION=3.0
       addons:
         apt:
           sources: [ mongodb-3.0-precise ]
           packages: [ mongodb-org, *common_packages ]
     - php: 7.0
-      env: DRIVER_VERSION=1.2.0 SERVER_VERSION=3.2
+      env: DRIVER_VERSION=1.3.0RC1 SERVER_VERSION=3.2
       addons:
         apt:
           sources: [ mongodb-3.2-precise ]

composer.json

@@ -11,7 +11,7 @@
     ],
     "require": {
         "php": ">=5.4",
-        "ext-mongodb": "^1.2.0"
+        "ext-mongodb": "^1.3.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8"

src/Operation/Aggregate.php

@@ -182,6 +182,14 @@ class Aggregate implements Executable
             throw new InvalidArgumentException('"typeMap" option should not be used if "useCursor" is false');
         }
 
+        if (isset($options['readConcern']) && $options['readConcern']->isDefault()) {
+            unset($options['readConcern']);
+        }
+
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->pipeline = $pipeline;

src/Operation/BulkWrite.php

@@ -266,6 +266,10 @@ class BulkWrite implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->operations = $operations;

src/Operation/Count.php

@@ -117,6 +117,10 @@ class Count implements Executable
             throw InvalidArgumentException::invalidType('"skip" option', $options['skip'], 'integer');
         }
 
+        if (isset($options['readConcern']) && $options['readConcern']->isDefault()) {
+            unset($options['readConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->filter = $filter;

src/Operation/CreateCollection.php

@@ -157,6 +157,10 @@ class CreateCollection implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->options = $options;

src/Operation/CreateIndexes.php

@@ -96,6 +96,10 @@ class CreateIndexes implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->options = $options;

src/Operation/Delete.php

@@ -83,6 +83,10 @@ class Delete implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->filter = $filter;

src/Operation/Distinct.php

@@ -93,6 +93,10 @@ class Distinct implements Executable
             throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
         }
 
+        if (isset($options['readConcern']) && $options['readConcern']->isDefault()) {
+            unset($options['readConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->fieldName = (string) $fieldName;

src/Operation/DropCollection.php

@@ -69,6 +69,10 @@ class DropCollection implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->options = $options;

src/Operation/DropDatabase.php

@@ -66,6 +66,10 @@ class DropDatabase implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->options = $options;
     }

src/Operation/DropIndexes.php

@@ -75,6 +75,10 @@ class DropIndexes implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->indexName = $indexName;

src/Operation/Find.php

@@ -190,6 +190,10 @@ class Find implements Executable
             throw InvalidArgumentException::invalidType('"typeMap" option', $options['typeMap'], 'array');
         }
 
+        if (isset($options['readConcern']) && $options['readConcern']->isDefault()) {
+            unset($options['readConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->filter = $filter;

src/Operation/FindAndModify.php

@@ -157,6 +157,10 @@ class FindAndModify implements Executable
             throw new InvalidArgumentException('The "remove" option must be true or an "update" document must be specified, but not both');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->options = $options;

src/Operation/InsertMany.php

@@ -97,6 +97,10 @@ class InsertMany implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->documents = $documents;

src/Operation/InsertOne.php

@@ -73,6 +73,10 @@ class InsertOne implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->document = $document;

src/Operation/MapReduce.php

@@ -203,6 +203,14 @@ class MapReduce implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['readConcern']) && $options['readConcern']->isDefault()) {
+            unset($options['readConcern']);
+        }
+
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->map = $map;

src/Operation/Update.php

@@ -117,6 +117,10 @@ class Update implements Executable
             throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
         }
 
+        if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
+            unset($options['writeConcern']);
+        }
+
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->filter = $filter;

tests/CommandObserver.php

+<?php
+
+namespace MongoDB\Tests;
+
+use MongoDB\Driver\Monitoring\CommandFailedEvent;
+use MongoDB\Driver\Monitoring\CommandStartedEvent;
+use MongoDB\Driver\Monitoring\CommandSucceededEvent;
+use MongoDB\Driver\Monitoring\CommandSubscriber;
+
+/**
+ * Observes command documents using the driver's monitoring API.
+ */
+class CommandObserver implements CommandSubscriber
+{
+    private $commands = [];
+
+    public function observe(callable $execution, callable $commandCallback)
+    {
+        $this->commands = [];
+
+        \MongoDB\Driver\Monitoring\addSubscriber($this);
+
+        call_user_func($execution);
+
+        \MongoDB\Driver\Monitoring\removeSubscriber($this);
+
+        foreach ($this->commands as $command) {
+            call_user_func($commandCallback, $command);
+        }
+    }
+
+    public function commandStarted(CommandStartedEvent $event)
+    {
+        $this->commands[] = $event->getCommand();
+    }
+
+    public function commandSucceeded(CommandSucceededEvent $event)
+    {
+    }
+
+    public function commandFailed(CommandFailedEvent $event)
+    {
+    }
+}

tests/Operation/AggregateFunctionalTest.php

@@ -4,11 +4,55 @@ namespace MongoDB\Tests\Operation;
 
 use MongoDB\Driver\BulkWrite;
 use MongoDB\Operation\Aggregate;
+use MongoDB\Tests\CommandObserver;
+use stdClass;
 
 class AggregateFunctionalTest extends FunctionalTestCase
 {
     private static $wireVersionForCursor = 2;
 
+    public function testDefaultReadConcernIsOmitted()
+    {
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new Aggregate(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    [['$match' => ['x' => 1]]],
+                    ['readConcern' => $this->createDefaultReadConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('readConcern', $command);
+            }
+        );
+    }
+
+    public function testDefaultWriteConcernIsOmitted()
+    {
+        if (version_compare($this->getServerVersion(), '2.6.0', '<')) {
+            $this->markTestSkipped('$out pipeline operator is not supported');
+        }
+
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new Aggregate(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    [['$out' => $this->getCollectionName() . '.output']],
+                    ['writeConcern' => $this->createDefaultWriteConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('writeConcern', $command);
+            }
+        );
+    }
+
     /**
      * @expectedException MongoDB\Driver\Exception\RuntimeException
      */

tests/Operation/CountFunctionalTest.php

+<?php
+
+namespace MongoDB\Tests\Operation;
+
+use MongoDB\Operation\Count;
+use MongoDB\Tests\CommandObserver;
+use stdClass;
+
+class CountFunctionalTest extends FunctionalTestCase
+{
+    public function testDefaultReadConcernIsOmitted()
+    {
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new Count(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    [],
+                    ['readConcern' => $this->createDefaultReadConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('readConcern', $command);
+            }
+        );
+    }
+}

tests/Operation/CreateCollectionFunctionalTest.php

+<?php
+
+namespace MongoDB\Tests\Operation;
+
+use MongoDB\Operation\CreateCollection;
+use MongoDB\Tests\CommandObserver;
+use stdClass;
+
+class CreateCollectionFunctionalTest extends FunctionalTestCase
+{
+    public function testDefaultWriteConcernIsOmitted()
+    {
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new CreateCollection(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    ['writeConcern' => $this->createDefaultWriteConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('writeConcern', $command);
+            }
+        );
+    }
+}

tests/Operation/CreateIndexesFunctionalTest.php

@@ -6,7 +6,9 @@ use MongoDB\Model\IndexInfo;
 use MongoDB\Operation\CreateIndexes;
 use MongoDB\Operation\DropIndexes;
 use MongoDB\Operation\ListIndexes;
+use MongoDB\Tests\CommandObserver;
 use InvalidArgumentException;
+use stdClass;
 
 class CreateIndexesFunctionalTest extends FunctionalTestCase
 {
@@ -157,6 +159,32 @@ class CreateIndexesFunctionalTest extends FunctionalTestCase
         });
     }
 
+    public function testDefaultWriteConcernIsOmitted()
+    {
+        /* Earlier server versions do not support the createIndexes command. Per
+         * the Index Management specification, inserts on system.indexes must
+         * use the write concern {w:1}. */
+        if (version_compare($this->getServerVersion(), '2.6.0', '<')) {
+            $this->markTestSkipped('createIndexes command is not supported');
+        }
+
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new CreateIndexes(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    [['key' => ['x' => 1]]],
+                    ['writeConcern' => $this->createDefaultWriteConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('writeConcern', $command);
+            }
+        );
+    }
+
     /**
      * Asserts that an index with the given name exists for the collection.
      *

tests/Operation/DistinctFunctionalTest.php

+<?php
+
+namespace MongoDB\Tests\Operation;
+
+use MongoDB\Operation\Distinct;
+use MongoDB\Tests\CommandObserver;
+use stdClass;
+
+class DistinctFunctionalTest extends FunctionalTestCase
+{
+    public function testDefaultReadConcernIsOmitted()
+    {
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new Distinct(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    'x',
+                    [],
+                    ['readConcern' => $this->createDefaultReadConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('readConcern', $command);
+            }
+        );
+    }
+}

tests/Operation/DropCollectionFunctionalTest.php

@@ -5,9 +5,29 @@ namespace MongoDB\Tests\Operation;
 use MongoDB\Operation\DropCollection;
 use MongoDB\Operation\InsertOne;
 use MongoDB\Operation\ListCollections;
+use MongoDB\Tests\CommandObserver;
+use stdClass;
 
 class DropCollectionFunctionalTest extends FunctionalTestCase
 {
+    public function testDefaultWriteConcernIsOmitted()
+    {
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new DropCollection(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    ['writeConcern' => $this->createDefaultWriteConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('writeConcern', $command);
+            }
+        );
+    }
+
     public function testDropExistingCollection()
     {
         $server = $this->getPrimaryServer();

tests/Operation/DropDatabaseFunctionalTest.php

@@ -6,9 +6,28 @@ use MongoDB\Driver\Server;
 use MongoDB\Operation\DropDatabase;
 use MongoDB\Operation\InsertOne;
 use MongoDB\Operation\ListDatabases;
+use MongoDB\Tests\CommandObserver;
+use stdClass;
 
 class DropDatabaseFunctionalTest extends FunctionalTestCase
 {
+    public function testDefaultWriteConcernIsOmitted()
+    {
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new DropDatabase(
+                    $this->getDatabaseName(),
+                    ['writeConcern' => $this->createDefaultWriteConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('writeConcern', $command);
+            }
+        );
+    }
+
     public function testDropExistingDatabase()
     {
         $server = $this->getPrimaryServer();

tests/Operation/DropIndexesFunctionalTest.php

@@ -5,10 +5,34 @@ namespace MongoDB\Tests\Operation;
 use MongoDB\Operation\CreateIndexes;
 use MongoDB\Operation\DropIndexes;
 use MongoDB\Operation\ListIndexes;
+use MongoDB\Tests\CommandObserver;
 use InvalidArgumentException;
+use stdClass;
 
 class DropIndexesFunctionalTest extends FunctionalTestCase
 {
+    public function testDefaultWriteConcernIsOmitted()
+    {
+        $operation = new CreateIndexes($this->getDatabaseName(), $this->getCollectionName(), [['key' => ['x' => 1]]]);
+        $operation->execute($this->getPrimaryServer());
+
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new DropIndexes(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    'x_1',
+                    ['writeConcern' => $this->createDefaultWriteConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('writeConcern', $command);
+            }
+        );
+    }
+
     public function testDropOneIndexByName()
     {
         $indexes = [['key' => ['x' => 1]]];

tests/Operation/FindAndModifyFunctionalTest.php

@@ -5,9 +5,29 @@ namespace MongoDB\Tests\Operation;
 use MongoDB\Driver\BulkWrite;
 use MongoDB\Model\BSONDocument;
 use MongoDB\Operation\FindAndModify;
+use MongoDB\Tests\CommandObserver;
+use stdClass;
 
 class FindAndModifyFunctionalTest extends FunctionalTestCase
 {
+    public function testDefaultWriteConcernIsOmitted()
+    {
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new FindAndModify(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    ['remove' => true, 'writeConcern' => $this->createDefaultWriteConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('writeConcern', $command);
+            }
+        );
+    }
+
     /**
      * @dataProvider provideTypeMapOptionsAndExpectedDocument
      */

tests/Operation/FindFunctionalTest.php

@@ -4,9 +4,30 @@ namespace MongoDB\Tests\Operation;
 
 use MongoDB\Driver\BulkWrite;
 use MongoDB\Operation\Find;
+use MongoDB\Tests\CommandObserver;
+use stdClass;
 
 class FindFunctionalTest extends FunctionalTestCase
 {
+    public function testDefaultReadConcernIsOmitted()
+    {
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new Find(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    [],
+                    ['readConcern' => $this->createDefaultReadConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('readConcern', $command);
+            }
+        );
+    }
+
     /**
      * @dataProvider provideTypeMapOptionsAndExpectedDocuments
      */

tests/Operation/FunctionalTestCase.php

@@ -3,7 +3,9 @@
 namespace MongoDB\Tests\Operation;
 
 use MongoDB\Collection;
+use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
+use MongoDB\Driver\WriteConcern;
 use MongoDB\Operation\DropCollection;
 use MongoDB\Tests\FunctionalTestCase as BaseFunctionalTestCase;
 
@@ -29,4 +31,14 @@ abstract class FunctionalTestCase extends BaseFunctionalTestCase
         $operation = new DropCollection($this->getDatabaseName(), $this->getCollectionName());
         $operation->execute($this->getPrimaryServer());
     }
+
+    protected function createDefaultReadConcern()
+    {
+        return new ReadConcern;
+    }
+
+    protected function createDefaultWriteConcern()
+    {
+        return new WriteConcern(-2);
+    }
 }

tests/Operation/MapReduceFunctionalTest.php

@@ -4,12 +4,66 @@ namespace MongoDB\Tests\Operation;
 
 use MongoDB\BSON\Javascript;
 use MongoDB\Driver\BulkWrite;
+use MongoDB\Operation\CreateCollection;
 use MongoDB\Operation\DropCollection;
 use MongoDB\Operation\Find;
 use MongoDB\Operation\MapReduce;
+use MongoDB\Tests\CommandObserver;
+use stdClass;
 
 class MapReduceFunctionalTest extends FunctionalTestCase
 {
+    public function testDefaultReadConcernIsOmitted()
+    {
+        $operation = new CreateCollection($this->getDatabaseName(), $this->getCollectionName());
+        $operation->execute($this->getPrimaryServer());
+
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new MapReduce(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    new Javascript('function() { emit(this.x, this.y); }'),
+                    new Javascript('function(key, values) { return Array.sum(values); }'),
+                    ['inline' => 1],
+                    ['readConcern' => $this->createDefaultReadConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('readConcern', $command);
+            }
+        );
+    }
+
+    public function testDefaultWriteConcernIsOmitted()
+    {
+        $operation = new CreateCollection($this->getDatabaseName(), $this->getCollectionName());
+        $operation->execute($this->getPrimaryServer());
+
+        (new CommandObserver)->observe(
+            function() {
+                $operation = new MapReduce(
+                    $this->getDatabaseName(),
+                    $this->getCollectionName(),
+                    new Javascript('function() { emit(this.x, this.y); }'),
+                    new Javascript('function(key, values) { return Array.sum(values); }'),
+                    $this->getCollectionName() . '.output',
+                    ['writeConcern' => $this->createDefaultWriteConcern()]
+                );
+
+                $operation->execute($this->getPrimaryServer());
+            },
+            function(stdClass $command) {
+                $this->assertObjectNotHasAttribute('writeConcern', $command);
+            }
+        );
+
+        $operation = new DropCollection($this->getDatabaseName(), $this->getCollectionName() . '.output');
+        $operation->execute($this->getPrimaryServer());
+    }
+
     public function testResult()
     {
         $this->createFixtures(3);