@@ -548,7 +548,7 @@ describe('Collection', function() {
       const ObjectID = configuration.require.ObjectID;
       db.createCollection('save_error_on_save_test', (err, collection) => {
         // Create unique index for username
-        collection.createIndex([['username', 1]], configuration.writeConcernMax(), err => {
+        collection.createIndex({ username: 1 }, configuration.writeConcernMax(), err => {
           expect(err).to.not.exist;
           const doc = {
             email: 'email@email.com',
'use strict';
const setupDatabase = require('./shared').setupDatabase;
const chai = require('chai');
const expect = chai.expect;
const sinonChai = require('sinon-chai');
const mock = require('mongodb-mock-server');
chai.use(sinonChai);

describe('Collection', function() {
  let configuration;
  before(function() {
    configuration = this.configuration;
    return setupDatabase(configuration, ['listCollectionsDb', 'listCollectionsDb2', 'test_db']);
  });

  describe('standard collection tests', function() {
    let client;
    let db;
    beforeEach(function() {
      client = configuration.newClient(configuration.writeConcernMax(), {
        poolSize: 1
      });
      return client.connect().then(client => {
        db = client.db(configuration.db);
      });
    });

    afterEach(function() {
      db = undefined;
      return client.close();
    });

    /**
     * @ignore
     */
    it('should correctly execute basic collection methods', function(done) {
      db.createCollection('test_collection_methods', (err, collection) => {
        // Verify that all the result are correct coming back (should contain the value ok)
        expect(collection.collectionName).to.equal('test_collection_methods');
        // Let's check that the collection was created correctly
        db.listCollections().toArray((err, documents) => {
          expect(err).to.not.exist;
          let found = false;
          documents.forEach(doc => {
            if (doc.name === 'test_collection_methods') found = true;
          });
          expect(found).to.be.true;
          // Rename the collection and check that it's gone
          db.renameCollection('test_collection_methods', 'test_collection_methods2', err => {
            expect(err).to.not.exist;
            // Drop the collection and check that it's gone
            db.dropCollection('test_collection_methods2', (err, result) => {
              expect(result).to.be.true;
            });
          });

          db.createCollection('test_collection_methods3', (err, collection) => {
            // Verify that all the result are correct coming back (should contain the value ok)
            expect(collection.collectionName).to.equal('test_collection_methods3');

            db.createCollection('test_collection_methods4', (err, collection) => {
              // Verify that all the result are correct coming back (should contain the value ok)
              expect(collection.collectionName).to.equal('test_collection_methods4');
              // Rename the collection and with the dropTarget boolean, and check to make sure only onen exists.
              db.renameCollection(
                'test_collection_methods4',
                'test_collection_methods3',
                { dropTarget: true },
                err => {
                  expect(err).to.not.exist;

                  db.dropCollection('test_collection_methods3', (err, result) => {
                    expect(result).to.be.true;
                    done();
                  });
                }
              );
            });
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should correctly access collection names', function(done) {
      // Create two collections
      db.createCollection('test.spiderman', () => {
        db.createCollection('test.mario', () => {
          // Insert test documents (creates collections)
          db.collection('test.spiderman', (err, spiderman_collection) => {
            spiderman_collection.insertOne({ foo: 5 }, configuration.writeConcernMax(), err => {
              expect(err).to.not.exist;
              db.collection('test.mario', (err, mario_collection) => {
                mario_collection.insertOne({ bar: 0 }, configuration.writeConcernMax(), err => {
                  expect(err).to.not.exist;
                  // Assert collections
                  db.collections((err, collections) => {
                    let found_spiderman = false;
                    let found_mario = false;
                    let found_does_not_exist = false;

                    collections.forEach(collection => {
                      if (collection.collectionName === 'test.spiderman') {
                        found_spiderman = true;
                      }
                      if (collection.collectionName === 'test.mario') found_mario = true;
                      if (collection.collectionName === 'does_not_exist')
                        found_does_not_exist = true;
                    });

                    expect(found_spiderman).to.be.true;
                    expect(found_mario).to.be.true;
                    expect(found_does_not_exist).to.be.false;
                    done();
                  });
                });
              });
            });
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should correctly retrieve listCollections', function(done) {
      db.createCollection('test_collection_names', err => {
        expect(err).to.not.exist;

        db.listCollections().toArray((err, documents) => {
          let found = false;
          let found2 = false;

          documents.forEach(document => {
            if (
              document.name === configuration.db + '.test_collection_names' ||
              document.name === 'test_collection_names'
            )
              found = true;
          });

          expect(found).to.be.true;
          // Insert a document in an non-existing collection should create the collection
          const collection = db.collection('test_collection_names2');
          collection.insertOne({ a: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            db.listCollections().toArray((err, documents) => {
              documents.forEach(document => {
                if (
                  document.name === configuration.db + '.test_collection_names2' ||
                  document.name === 'test_collection_names2'
                )
                  found = true;
                if (
                  document.name === configuration.db + '.test_collection_names' ||
                  document.name === 'test_collection_names'
                )
                  found2 = true;
              });

              expect(found).to.be.true;
              expect(found2).to.be.true;

              // Let's close the db
              done();
            });
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should ensure strict access collection', function(done) {
      db.collection('does-not-exist', { strict: true }, err => {
        expect(err).to.be.an.instanceof(Error);
        expect(err.message).to.equal(
          'Collection does-not-exist does not exist. Currently in strict mode.'
        );
        db.createCollection('test_strict_access_collection', err => {
          expect(err).to.not.exist;
          db.collection('test_strict_access_collection', configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;
            // Let's close the db
            done();
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should perform strict create collection', function(done) {
      db.createCollection('test_strict_create_collection', (err, collection) => {
        expect(err).to.not.exist;
        expect(collection.collectionName).to.equal('test_strict_create_collection');

        // Creating an existing collection should fail
        db.createCollection('test_strict_create_collection', { strict: true }, err => {
          expect(err).to.be.an.instanceof(Error);
          expect(err.message).to.equal(
            'Collection test_strict_create_collection already exists. Currently in strict mode.'
          );

          done();
        });
      });
    });

    /**
     * @ignore
     */
    it('should fail to insert due to illegal keys', function(done) {
      db.createCollection('test_invalid_key_names', (err, collection) => {
        // Legal inserts
        collection.insertMany(
          [{ hello: 'world' }, { hello: { hello: 'world' } }],
          configuration.writeConcernMax(),
          err => {
            expect(err).to.not.exist;

            // Illegal insert for key
            collection.insertOne({ $hello: 'world' }, configuration.writeConcernMax(), err => {
              expect(err).to.be.an.instanceof(Error);
              expect(err.message).to.equal("key $hello must not start with '$'");

              collection.insertOne(
                { hello: { $hello: 'world' } },
                configuration.writeConcernMax(),
                err => {
                  expect(err).to.be.an.instanceof(Error);
                  expect(err.message).to.equal("key $hello must not start with '$'");

                  collection.insertOne(
                    { he$llo: 'world' },
                    configuration.writeConcernMax(),
                    err => {
                      expect(err).to.not.exist;

                      collection.insertOne(
                        { hello: { hell$o: 'world' } },
                        configuration.writeConcernMax(),
                        err => {
                          expect(err).to.not.exist;

                          collection.insertOne(
                            { '.hello': 'world' },
                            configuration.writeConcernMax(),
                            err => {
                              expect(err).to.be.an.instanceof(Error);
                              expect(err.message).to.equal("key .hello must not contain '.'");

                              collection.insertOne(
                                { hello: { '.hello': 'world' } },
                                configuration.writeConcernMax(),
                                err => {
                                  expect(err).to.be.an.instanceof(Error);
                                  expect(err.message).to.equal("key .hello must not contain '.'");

                                  collection.insertOne(
                                    { 'hello.': 'world' },
                                    configuration.writeConcernMax(),
                                    err => {
                                      expect(err).to.be.an.instanceof(Error);
                                      expect(err.message).to.equal(
                                        "key hello. must not contain '.'"
                                      );

                                      collection.insertOne(
                                        { hello: { 'hello.': 'world' } },
                                        configuration.writeConcernMax(),
                                        err => {
                                          expect(err).to.be.an.instanceof(Error);
                                          expect(err.message).to.equal(
                                            "key hello. must not contain '.'"
                                          );
                                          // Let's close the db
                                          done();
                                        }
                                      );
                                    }
                                  );
                                }
                              );
                            }
                          );
                        }
                      );
                    }
                  );
                }
              );
            });
          }
        );
      });
    });

    /**
     * @ignore
     */
    it('should fail due to illegal listCollections', function(done) {
      db.collection(5, err => {
        expect(err.message).to.equal('collection name must be a String');
      });

      db.collection('', err => {
        expect(err.message).to.equal('collection names cannot be empty');
      });

      db.collection('te$t', err => {
        expect(err.message).to.equal("collection names must not contain '$'");
      });

      db.collection('.test', err => {
        expect(err.message).to.equal("collection names must not start or end with '.'");
      });

      db.collection('test.', err => {
        expect(err.message).to.equal("collection names must not start or end with '.'");
      });

      db.collection('test..t', err => {
        expect(err.message).to.equal('collection names cannot be empty');
        done();
      });
    });

    it('should return invalid collection name error by callback for createCollection', function(done) {
      db.dropDatabase(err => {
        expect(err).to.not.exist;

        db.createCollection('test/../', err => {
          expect(err).to.be.instanceof(Error);
          expect(err.message).to.equal('collection names cannot be empty');
          done();
        });
      });
    });
    /**
     * @ignore
     */
    it('should correctly count on non-existent collection', function(done) {
      db.collection('test_multiple_insert_2', (err, collection) => {
        collection.countDocuments((err, count) => {
          expect(count).to.equal(0);
          // Let's close the db
          done();
        });
      });
    });

    /**
     * @ignore
     */
    it('should correctly execute save', function(done) {
      db.createCollection('test_save', (err, collection) => {
        const doc = { hello: 'world' };
        collection.save(doc, configuration.writeConcernMax(), (err, r) => {
          expect(r.ops[0]._id).to.exist;

          collection.countDocuments((err, count) => {
            expect(count).to.equal(1);

            collection.save(r.ops[0], configuration.writeConcernMax(), err => {
              expect(err).to.not.exist;
              collection.countDocuments((err, count) => {
                expect(count).to.equal(1);

                collection.findOne((err, doc3) => {
                  expect(doc3.hello).to.equal('world');

                  doc3.hello = 'mike';

                  collection.save(doc3, configuration.writeConcernMax(), err => {
                    expect(err).to.not.exist;
                    collection.countDocuments((err, count) => {
                      expect(count).to.equal(1);

                      collection.findOne((err, doc5) => {
                        expect(doc5.hello).to.equal('mike');

                        // Save another document
                        collection.save(
                          { hello: 'world' },
                          configuration.writeConcernMax(),
                          err => {
                            expect(err).to.not.exist;
                            collection.countDocuments((err, count) => {
                              expect(count).to.equal(2);
                              // Let's close the db
                              done();
                            });
                          }
                        );
                      });
                    });
                  });
                });
              });
            });
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should correctly save document with Long value', function(done) {
      const Long = configuration.require.Long;
      db.createCollection('test_save_long', (err, collection) => {
        collection.insertOne(
          { x: Long.fromNumber(9223372036854775807) },
          configuration.writeConcernMax(),
          err => {
            expect(err).to.not.exist;
            collection.findOne((err, doc) => {
              expect(err).to.not.exist;
              expect(doc.x).to.deep.equal(Long.fromNumber(9223372036854775807));
              // Let's close the db
              done();
            });
          }
        );
      });
    });

    /**
     * @ignore
     */
    it('should save object that has id but does not exist in collection', function(done) {
      db.createCollection(
        'test_save_with_object_that_has_id_but_does_not_actually_exist_in_collection',
        (err, collection) => {
          const a = { _id: '1', hello: 'world' };
          collection.save(a, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;
            collection.countDocuments((err, count) => {
              expect(count).to.equal(1);

              collection.findOne((err, doc) => {
                expect(doc.hello).to.equal('world');

                doc.hello = 'mike';
                collection.save(doc, configuration.writeConcernMax(), err => {
                  expect(err).to.not.exist;
                  collection.findOne((err, doc) => {
                    collection.countDocuments((err, count) => {
                      expect(count).to.equal(1);

                      expect(doc.hello).to.equal('mike');
                      // Let's close the db
                      done();
                    });
                  });
                });
              });
            });
          });
        }
      );
    });

    /**
     * @ignore
     */
    it('should correctly execute insert update delete safe mode', function(done) {
      db.createCollection(
        'test_should_execute_insert_update_delete_safe_mode',
        (err, collection) => {
          expect(collection.collectionName).to.equal(
            'test_should_execute_insert_update_delete_safe_mode'
          );

          collection.insertOne({ i: 1 }, configuration.writeConcernMax(), (err, r) => {
            expect(r.ops.length).to.equal(1);
            expect(r.ops[0]._id.toHexString().length).to.equal(24);

            // Update the record
            collection.updateOne(
              { i: 1 },
              { $set: { i: 2 } },
              configuration.writeConcernMax(),
              err => {
                expect(err).to.not.exist;
                expect(r.result.n).to.equal(1);

                // Remove safely
                collection.deleteOne({}, configuration.writeConcernMax(), err => {
                  expect(err).to.not.exist;

                  done();
                });
              }
            );
          });
        }
      );
    });

    /**
     * @ignore
     */
    it('should perform multiple saves', function(done) {
      db.createCollection('multiple_save_test', (err, collection) => {
        const doc = {
          name: 'amit',
          text: 'some text'
        };

        //insert new user
        collection.save(doc, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          collection
            .find({}, { name: 1 })
            .limit(1)
            .toArray((err, users) => {
              const user = users[0];

              if (err) {
                throw new Error(err);
              } else if (user) {
                user.pants = 'worn';

                collection.save(user, configuration.writeConcernMax(), (err, result) => {
                  expect(err).to.not.exist;
                  expect(result.result.n).to.equal(1);
                  done();
                });
              }
            });
        });
      });
    });

    /**
     * @ignore
     */
    it('should correctly save document with nested array', function(done) {
      const ObjectID = configuration.require.ObjectID;
      db.createCollection('save_error_on_save_test', (err, collection) => {
        // Create unique index for username
        collection.createIndex([['username', 1]], configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;
          const doc = {
            email: 'email@email.com',
            encrypted_password: 'password',
            friends: [
              '4db96b973d01205364000006',
              '4db94a1948a683a176000001',
              '4dc77b24c5ba38be14000002'
            ],
            location: [72.4930088, 23.0431957],
            name: 'Amit Kumar',
            password_salt: 'salty',
            profile_fields: [],
            username: 'amit'
          };
          //insert new user
          collection.save(doc, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            collection
              .find({})
              .limit(1)
              .toArray((err, users) => {
                expect(err).to.not.exist;
                const user = users[0];
                user.friends.splice(1, 1);

                collection.save(user, err => {
                  expect(err).to.not.exist;

                  // Update again
                  collection.updateOne(
                    { _id: new ObjectID(user._id.toString()) },
                    { $set: { friends: user.friends } },
                    { upsert: true, w: 1 },
                    (err, result) => {
                      expect(err).to.not.exist;
                      expect(result.result.n).to.equal(1);

                      done();
                    }
                  );
                });
              });
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should perform collection remove with no callback', function(done) {
      db.collection('remove_with_no_callback_bug_test', (err, collection) => {
        expect(err).to.not.exist;
        collection.insertOne({ a: 1 }, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;
          collection.insertOne({ b: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;
            collection.insertOne({ c: 1 }, configuration.writeConcernMax(), err => {
              expect(err).to.not.exist;
              collection.remove({ a: 1 }, configuration.writeConcernMax(), err => {
                expect(err).to.not.exist;
                // Let's perform a count
                collection.countDocuments((err, count) => {
                  expect(err).to.not.exist;
                  expect(count).to.equal(2);
                  done();
                });
              });
            });
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should correctly read back document with null', function(done) {
      db.createCollection('shouldCorrectlyReadBackDocumentWithNull', {}, (err, collection) => {
        // Insert a document with a date
        collection.insertOne({ test: null }, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          collection.findOne((err, result) => {
            expect(err).to.not.exist;
            expect(result.test).to.not.exist;
            done();
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should throw error due to illegal update', function(done) {
      db.createCollection('shouldThrowErrorDueToIllegalUpdate', {}, (err, coll) => {
        coll.update({}, null, err => {
          expect(err.message).to.equal('document must be a valid JavaScript object');
        });
        coll.update(null, null, err => {
          expect(err.message).to.equal('selector must be a valid JavaScript object');
        });

        done();
      });
    });

    /**
     * @ignore
     */
    it('should correctly handle 0 as id for save', function(done) {
      db.collection('shouldCorrectlyHandle0asIdForSave').save({ _id: 0 }, err => {
        expect(err).to.not.exist;

        db.collection('shouldCorrectlyHandle0asIdForSave').save({ _id: 0 }, err => {
          expect(err).to.not.exist;
          done();
        });
      });
    });

    const selectorTests = [
      {
        title: 'should correctly execute update with . field in selector',
        collectionName: 'executeUpdateWithElemMatch',
        filterObject: { 'item.i': 1 },
        updateObject: { $set: { a: 1 } }
      },
      {
        title: 'should correctly execute update with elemMatch field in selector',
        collectionName: 'executeUpdateWithElemMatch',
        filterObject: { item: { $elemMatch: { name: 'my_name' } } },
        updateObject: { $set: { a: 1 } }
      }
    ];

    selectorTests.forEach(test => {
      it(test.title, function(done) {
        db.collection(test.collectionName).updateOne(
          test.filterObject,
          test.updateObject,
          (err, r) => {
            expect(err).to.not.exist;
            expect(r.result.n).to.equal(0);
            done();
          }
        );
      });
    });

    const updateTests = [
      {
        title: 'should correctly update with no docs',
        collectionName: 'test_should_correctly_do_update_with_no_docs',
        filterObject: { _id: 1 },
        updateObject: { $set: { _id: 1, a: 1 } }
      },
      {
        title: 'should correctly update with pipeline',
        collectionName: 'test_should_correctly_do_update_with_pipeline',
        filterObject: {},
        updateObject: { $set: { a: 1, b: 1, d: 1 } }
      }
    ];

    updateTests.forEach(test => {
      it(test.title, function(done) {
        db.createCollection(test.collectionName, (err, collection) => {
          collection.updateOne(
            test.filterObject,
            test.updateObject,
            configuration.writeConcernMax(),
            (err, r) => {
              expect(err).to.not.exist;
              expect(r.result.n).to.equal(0);

              done();
            }
          );
        });
      });
    });

    /**
     * @ignore
     */
    it('should fail due to existing collection', function(done) {
      db.createCollection('shouldFailDueToExistingCollection', { strict: true }, (err, coll) => {
        expect(err).to.not.exist;
        expect(coll).to.exist;

        db.createCollection('shouldFailDueToExistingCollection', { strict: true }, err => {
          expect(err).to.exist;
          expect(err.message).to.equal(
            'Collection shouldFailDueToExistingCollection already exists. Currently in strict mode.'
          );
          done();
        });
      });
    });

    const listCollectionsTests = [
      {
        title: 'should filter correctly during list',
        collectionName: 'integration_tests_collection_123'
      },
      {
        title: 'should correctly list back collection names containing .',
        collectionName: 'test.game'
      }
    ];

    listCollectionsTests.forEach(test => {
      it(test.title, function(done) {
        db.createCollection(test.collectionName, (err, collection) => {
          expect(err).to.not.exist;
          expect(collection.collectionName).to.equal(test.collectionName);
          db.listCollections().toArray((err, documents) => {
            expect(err).to.not.exist;
            let found = false;
            documents.forEach(x => {
              if (x.name === test.collectionName) found = true;
            });

            expect(found).to.be.true;
            done();
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should filter correctly with index during list', function(done) {
      const testCollection = 'collection_124';
      // Create a collection
      db.createCollection(testCollection, err => {
        expect(err).to.not.exist;

        // Index name happens to be the same as collection name
        db.createIndex(testCollection, 'collection_124', { w: 1 }, (err, indexName) => {
          expect(err).to.not.exist;
          expect(indexName).to.equal('collection_124_1');

          db.listCollections().toArray((err, documents) => {
            expect(err).to.not.exist;
            expect(documents.length > 1).to.be.true;
            let found = false;

            documents.forEach(document => {
              if (document.name === testCollection) found = true;
            });

            expect(found).to.be.true;
            done();
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should correctly list multipleCollections', function(done) {
      const emptyDb = client.db('listCollectionsDb');
      emptyDb.createCollection('test1', err => {
        expect(err).to.not.exist;

        emptyDb.createCollection('test2', err => {
          expect(err).to.not.exist;

          emptyDb.createCollection('test3', err => {
            expect(err).to.not.exist;

            emptyDb.listCollections().toArray((err, collections) => {
              expect(err).to.not.exist;
              let names = [];
              for (let i = 0; i < collections.length; i++) {
                names.push(collections[i].name);
              }
              expect(names).to.include('test1');
              expect(names).to.include('test2');
              expect(names).to.include('test3');
              done();
            });
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should correctly handle namespace when using collections method', function(done) {
      const emptyDb = client.db('listCollectionsDb2');
      emptyDb.createCollection('test1', err => {
        expect(err).to.not.exist;

        emptyDb.createCollection('test.test', err => {
          expect(err).to.not.exist;

          emptyDb.createCollection('test3', err => {
            expect(err).to.not.exist;

            emptyDb.collections((err, collections) => {
              collections = collections.map(collection => {
                return {
                  collectionName: collection.collectionName,
                  namespace: collection.namespace
                };
              });

              let foundCollection = false;
              collections.forEach(x => {
                if (
                  x.namespace === 'listCollectionsDb2.test.test' &&
                  x.collectionName === 'test.test'
                ) {
                  foundCollection = true;
                }
              });

              expect(foundCollection).to.be.true;
              done();
            });
          });
        });
      });
    });

    /**
     * @ignore
     */
    it('should provide access to the database name', function() {
      return client
        .db('test_db')
        .createCollection('test1')
        .then(coll => {
          expect(coll.dbName).to.equal('test_db');
        });
    });

    const collectionTTLtests = [
      {
        title: 'should correctly create TTL collection with index using createIndex',
        collectionName: 'shouldCorrectlyCreateTTLCollectionWithIndexCreateIndex'
      },
      {
        title: 'should correctly create TTL collection with index using ensureIndex',
        collectionName: 'shouldCorrectlyCreateTTLCollectionWithIndexUsingEnsureIndex'
      }
    ];

    collectionTTLtests.forEach(test => {
      it(test.title, function(done) {
        db.createCollection(test.collectionName, (err, collection) => {
          const errorCallBack = err => {
            expect(err).to.not.exist;

            // Insert a document with a date
            collection.insertOne(
              { a: 1, createdAt: new Date() },
              configuration.writeConcernMax(),
              err => {
                expect(err).to.not.exist;

                collection.indexInformation({ full: true }, (err, indexes) => {
                  expect(err).to.not.exist;

                  for (let i = 0; i < indexes.length; i++) {
                    if (indexes[i].name === 'createdAt_1') {
                      expect(indexes[i].expireAfterSeconds).to.equal(1);
                      break;
                    }
                  }

                  done();
                });
              }
            );
          };
          if (
            test.title === 'should correctly create TTL collection with index using createIndex'
          ) {
            collection.createIndex(
              { createdAt: 1 },
              { expireAfterSeconds: 1, w: 1 },
              errorCallBack
            );
          } else if (
            test.title === 'should correctly create TTL collection with index using ensureIndex'
          ) {
            collection.ensureIndex(
              { createdAt: 1 },
              { expireAfterSeconds: 1, w: 1 },
              errorCallBack
            );
          }
        });
      });
    });

    /**
     * @ignore
     */
    it('should support createIndex with no options', function(done) {
      db.createCollection('create_index_without_options', {}, (err, collection) => {
        collection.createIndex({ createdAt: 1 }, err => {
          expect(err).to.not.exist;

          collection.indexInformation({ full: true }, (err, indexes) => {
            expect(err).to.not.exist;
            const indexNames = indexes.map(i => i.name);
            expect(indexNames).to.include('createdAt_1');

            done();
          });
        });
      });
    });
  });

  describe('(countDocuments)', function() {
    let client;
    let db;
    let collection;
    beforeEach(function() {
      client = configuration.newClient({}, { w: 1 });

      return client.connect().then(client => {
        db = client.db(configuration.db);
        collection = db.collection('test_coll');
      });
    });
    afterEach(function() {
      return client.close();
    });

    const nonMatchQueryTests = [
      {
        title: 'should correctly perform estimatedDocumentCount on non-matching query'
      },
      {
        title: 'should correctly perform countDocuments on non-matching query'
      }
    ];

    nonMatchQueryTests.forEach(test => {
      it(test.title, function(done) {
        const close = e => client.close(() => done(e));
        let thenFunction;
        if (
          test.title === 'should correctly perform estimatedDocumentCount on non-matching query'
        ) {
          thenFunction = () => collection.estimatedDocumentCount({ a: 'b' });
        } else if (test.title === 'should correctly perform countDocuments on non-matching query') {
          thenFunction = () => collection.countDocuments({ a: 'b' });
        }
        Promise.resolve()
          .then(thenFunction)
          .then(count => expect(count).to.equal(0))
          .then(() => close())
          .catch(e => close(e));
      });
    });

    it('countDocuments should return Promise that resolves when no callback passed', function(done) {
      const docsPromise = collection.countDocuments();
      const close = e => client.close(() => done(e));

      expect(docsPromise).to.exist.and.to.be.an.instanceof(collection.s.promiseLibrary);

      docsPromise
        .then(result => expect(result).to.equal(0))
        .then(() => close())
        .catch(e => close(e));
    });

    it('countDocuments should not return a promise if callback given', function(done) {
      const close = e => client.close(() => done(e));

      const notPromise = collection.countDocuments({ a: 1 }, () => {
        expect(notPromise).to.be.undefined;
        close();
      });
    });

    it('countDocuments should correctly call the given callback', function(done) {
      const docs = [{ a: 1 }, { a: 2 }];
      const close = e => client.close(() => done(e));

      collection.insertMany(docs).then(() =>
        collection.countDocuments({ a: 1 }, (err, data) => {
          expect(data).to.equal(1);
          close(err);
        })
      );
    });
  });

  describe('countDocuments with mock server', function() {
    let server;

    beforeEach(() => {
      return mock.createServer().then(s => {
        server = s;
      });
    });

    afterEach(() => mock.cleanup());

    function testCountDocMock(testConfiguration, config, done) {
      const client = testConfiguration.newClient(`mongodb://${server.uri()}/test`);
      const close = e => client.close(() => done(e));

      server.setMessageHandler(request => {
        const doc = request.document;
        if (doc.aggregate) {
          try {
            config.replyHandler(doc);
            request.reply(config.reply);
          } catch (e) {
            close(e);
          }
        }

        if (doc.ismaster) {
          request.reply(Object.assign({}, mock.DEFAULT_ISMASTER));
        } else if (doc.endSessions) {
          request.reply({ ok: 1 });
        }
      });

      client.connect((err, client) => {
        const db = client.db('test');
        const collection = db.collection('countDoc_mock');

        config.executeCountDocuments(collection, close);
      });
    }

    it('countDocuments should return appropriate error if aggregation fails with callback given', function(done) {
      const replyHandler = () => {};
      const executeCountDocuments = (collection, close) => {
        collection.countDocuments(err => {
          expect(err).to.exist;
          expect(err.errmsg).to.equal('aggregation error - callback');
          close();
        });
      };

      testCountDocMock(
        configuration,
        {
          replyHandler,
          executeCountDocuments,
          reply: { ok: 0, errmsg: 'aggregation error - callback' }
        },
        done
      );
    });

    it('countDocuments should error if aggregation fails using Promises', function(done) {
      const replyHandler = () => {};
      const executeCountDocuments = (collection, close) => {
        collection
          .countDocuments()
          .then(() => expect(false).to.equal(true)) // should never get here; error should be caught
          .catch(e => {
            expect(e.errmsg).to.equal('aggregation error - promise');
            close();
          });
      };

      testCountDocMock(
        configuration,
        {
          replyHandler,
          executeCountDocuments,
          reply: { ok: 0, errmsg: 'aggregation error - promise' }
        },
        done
      );
    });

    it('countDocuments pipeline should be correct with skip and limit applied', function(done) {
      const replyHandler = doc => {
        expect(doc.pipeline).to.deep.include({ $skip: 1 });
        expect(doc.pipeline).to.deep.include({ $limit: 1 });
      };
      const executeCountDocuments = (collection, close) => {
        collection.countDocuments({}, { limit: 1, skip: 1 }, err => {
          expect(err).to.not.exist;
          close();
        });
      };

      testCountDocMock(
        configuration,
        {
          replyHandler,
          executeCountDocuments,
          reply: { ok: 1 }
        },
        done
      );
    });
  });

  function testCapped(testConfiguration, config, done) {
    const configuration = config.config;
    const client = testConfiguration.newClient({}, { w: 1 });

    client.connect((err, client) => {
      const db = client.db(configuration.db);
      const close = e => client.close(() => done(e));

      db.createCollection(config.collName, config.opts)
        .then(collection => collection.isCapped())
        .then(capped => expect(capped).to.be.false)
        .then(() => close())
        .catch(e => close(e));
    });
  }

  it('isCapped should return false for uncapped collections', function(done) {
    testCapped(
      configuration,
      { config: configuration, collName: 'uncapped', opts: { capped: false } },
      done
    );
  });

  it('isCapped should return false for collections instantiated without specifying capped', function(done) {
    testCapped(configuration, { config: configuration, collName: 'uncapped2', opts: {} }, done);
  });

  describe('Retryable Writes on bulk ops', function() {
    let client;
    let db;
    let collection;

    const metadata = { requires: { topology: ['replicaset'], mongodb: '>=3.6.0' } };

    beforeEach(function() {
      client = configuration.newClient({}, { retryWrites: true });
      return client.connect().then(() => {
        db = client.db('test_retry_writes');
        collection = db.collection('tests');

        return Promise.resolve()
          .then(() => db.dropDatabase())
          .then(() => collection.insertOne({ name: 'foobar' }));
      });
    });

    afterEach(function() {
      return client.close();
    });

    it('should succeed with retryWrite=true when using updateMany', {
      metadata,
      test: function() {
        return collection.updateMany({ name: 'foobar' }, { $set: { name: 'fizzbuzz' } });
      }
    });

    it('should succeed with retryWrite=true when using update with multi=true', {
      metadata,
      test: function() {
        return collection.updateOne(
          { name: 'foobar' },
          { $set: { name: 'fizzbuzz' } },
          { multi: true }
        );
      }
    });

    it('should succeed with retryWrite=true when using remove without option single', {
      metadata,
      test: function() {
        return collection.deleteOne({ name: 'foobar' });
      }
    });

    it('should succeed with retryWrite=true when using deleteMany', {
      metadata,
      test: function() {
        return collection.deleteMany({ name: 'foobar' });
      }
    });
  });

  it('should allow an empty replacement document for findOneAndReplace', {
    metadata: { requires: { mongodb: '>=3.0.0' } },
    test: function(done) {
      const configuration = this.configuration;
      const client = configuration.newClient({}, { w: 1 });

      let finish = err => {
        finish = () => {};
        client.close(_err => done(err || _err));
      };

      client.connect((err, client) => {
        expect(err).to.be.null;

        const db = client.db(configuration.db);
        const collection = db.collection('find_one_and_replace');

        collection.insertOne({ a: 1 }, err => {
          expect(err).to.be.null;

          try {
            collection.findOneAndReplace({ a: 1 }, {}, finish);
          } catch (e) {
            finish(e);
          }
        });
      });
    }
  });

  it('should correctly update with pipeline', {
    metadata: {
      requires: { mongodb: '>=4.2.0' }
    },

    // The actual test we wish to run
    test: function(done) {
      const configuration = this.configuration;
      const client = configuration.newClient(configuration.writeConcernMax(), {
        poolSize: 1
      });

      client.connect((err, client) => {
        const db = client.db(configuration.db);

        db.createCollection('test_should_correctly_do_update_with_pipeline', (err, collection) => {
          collection.updateOne(
            {},
            [{ $set: { a: 1 } }, { $set: { b: 1 } }, { $set: { d: 1 } }],
            configuration.writeConcernMax(),
            (err, r) => {
              expect(err).to.not.exist;
              expect(r.result.n).to.equal(0);

              client.close(done);
            }
          );
        });
      });
    }
  });
});

This test broke, is `createIndex` supposed to support that array syntax?