diff --git a/.travis.yml b/.travis.yml
index ddcb0f18..24395319 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,17 +1,18 @@
 language: node_js
 
 node_js:
-  - "6"
-  - "8"
+  - "12"
   - "10"
+  - "8"
 
 services:
   - docker
 
 env:
-  - MONGODB_VERSION="2.6"
-  - MONGODB_VERSION="3.6"
+  - MONGODB_VERSION="4.2"
   - MONGODB_VERSION="4.0"
+  - MONGODB_VERSION="3.6"
+  - MONGODB_VERSION="3.4"
 
 before_install:
   - docker run -d -p 127.0.0.1:27017:27017 mongo:$MONGODB_VERSION
diff --git a/index.js b/index.js
index db1e4b2a..d3c7d552 100644
--- a/index.js
+++ b/index.js
@@ -77,7 +77,7 @@ ShareDbMongo.prototype.getCollection = function(collectionName, callback) {
   // Gotcha: calls back sync if connected or async if not
   this.getDbs(function(err, mongo) {
     if (err) return callback(err);
-    var collection = mongo.collection(collectionName);
+    var collection = mongo.db().collection(collectionName);
     return callback(null, collection);
   });
 };
@@ -89,7 +89,7 @@ ShareDbMongo.prototype._getCollectionPoll = function(collectionName, callback) {
   // Gotcha: calls back sync if connected or async if not
   this.getDbs(function(err, mongo, mongoPoll) {
     if (err) return callback(err);
-    var collection = (mongoPoll || mongo).collection(collectionName);
+    var collection = (mongoPoll || mongo).db().collection(collectionName);
     return callback(null, collection);
   });
 };
@@ -312,7 +312,7 @@ ShareDbMongo.prototype.getOpCollection = function(collectionName, callback) {
   this.getDbs(function(err, mongo) {
     if (err) return callback(err);
     var name = self.getOplogCollectionName(collectionName);
-    var collection = mongo.collection(name);
+    var collection = mongo.db().collection(name);
     // Given the potential problems with creating indexes on the fly, it might
     // be preferrable to disable automatic creation
     if (self.disableIndexCreation) {
@@ -1311,7 +1311,7 @@ function MongoSnapshot(id, version, type, data, meta, opLink) {
   this.v = version;
   this.type = type;
   this.data = data;
-  this.m = meta == null ? null : meta;
+  this.m = (meta == null) ? null : meta;
   if (opLink) this._opLink = opLink;
 }
 
@@ -1364,23 +1364,9 @@ var collectionOperationsMap = {
     collection.distinct(value.field, query, cb);
   },
   $aggregate: function(collection, query, value, cb) {
-    collection.aggregate(value, function(err, resultsOrCursor) {
-      if (err) {
-        return cb(err);
-      }
-      if (Array.isArray(resultsOrCursor)) {
-        // 2.x Mongo driver directly produces a results array:
-        // https://mongodb.github.io/node-mongodb-native/2.2/api/Collection.html#aggregate
-        var resultsArray = resultsOrCursor;
-        cb(null, resultsArray);
-      } else {
-        // 3.x Mongo driver produces an AggregationCursor:
-        // https://mongodb.github.io/node-mongodb-native/3.0/api/Collection.html#aggregate
-        //
-        // ShareDB expects serializable result data, so use `Cursor#toArray` for that.
-        var cursor = resultsOrCursor;
-        cursor.toArray(cb);
-      }
+    collection.aggregate(value, function(err, cursor) {
+      if (err) return cb(err);
+      cursor.toArray(cb);
     });
   },
   $mapReduce: function(collection, query, value, cb) {
diff --git a/package.json b/package.json
index 49e729df..77e8339d 100644
--- a/package.json
+++ b/package.json
@@ -4,25 +4,29 @@
   "description": "MongoDB database adapter for ShareDB",
   "main": "index.js",
   "dependencies": {
-    "async": "^1.4.2",
-    "mongodb": "^2.1.2",
+    "async": "^1.5.2"
+  },
+  "peerDependencies": {
+    "mongodb": "^3.0.0",
     "sharedb": "^1.0.0-beta"
   },
   "devDependencies": {
-    "coveralls": "^2.11.8",
+    "chai": "^4.2.0",
+    "coveralls": "^3.0.7",
     "eslint": "^5.16.0",
     "eslint-config-google": "^0.13.0",
-    "expect.js": "^0.3.1",
-    "istanbul": "^0.4.2",
-    "mocha": "^2.3.3",
-    "sharedb-mingo-memory": "^1.0.2",
+    "mocha": "^6.2.2",
+    "mongodb": "^3.3.3",
+    "nyc": "^14.1.1",
+    "sharedb": "^1.0.0-beta",
+    "sharedb-mingo-memory": "^1.1.1",
     "sinon": "^6.1.5"
   },
   "scripts": {
     "lint": "./node_modules/.bin/eslint --ignore-path .gitignore '**/*.js'",
     "lint:fix": "npm run lint -- --fix",
     "test": "npm run lint && node_modules/.bin/mocha",
-    "test-cover": "npm run lint && node_modules/istanbul/lib/cli.js cover node_modules/mocha/bin/_mocha"
+    "test-cover": "npm run lint && node_modules/nyc/bin/nyc.js --temp-dir=coverage -r text -r lcov node_modules/mocha/bin/_mocha"
   },
   "repository": "git://github.com/share/sharedb-mongo.git",
   "author": "Nate Smith and Joseph Gentle",
diff --git a/test/test_get_ops_without_strict_linking.js b/test/test_get_ops_without_strict_linking.js
index c789946c..ce11631f 100644
--- a/test/test_get_ops_without_strict_linking.js
+++ b/test/test_get_ops_without_strict_linking.js
@@ -1,4 +1,4 @@
-var expect = require('expect.js');
+var expect = require('chai').expect;
 var mongodb = require('mongodb');
 var ShareDbMongo = require('..');
 var getQuery = require('sharedb-mingo-memory/get-query');
@@ -11,7 +11,7 @@ function create(callback) {
     mongo: function(shareDbCallback) {
       mongodb.connect(mongoUrl, function(err, mongo) {
         if (err) return callback(err);
-        mongo.dropDatabase(function(err) {
+        mongo.db().dropDatabase(function(err) {
           if (err) return callback(err);
           shareDbCallback(null, mongo);
           callback(null, db, mongo);
@@ -67,11 +67,11 @@ describe('getOpsWithoutStrictLinking: true', function() {
     it('fetches ops 0-1 without fetching all ops', function(done) {
       db.getOps(collection, id, 0, 2, null, function(error, ops) {
         if (error) return done(error);
-        expect(ops.length).to.be(2);
-        expect(ops[0].v).to.be(0);
-        expect(ops[1].v).to.be(1);
-        expect(db._getSnapshotOpLink.notCalled).to.be(true);
-        expect(db._getOps.calledOnceWith(collection, id, 0, 2)).to.be(true);
+        expect(ops.length).to.equal(2);
+        expect(ops[0].v).to.equal(0);
+        expect(ops[1].v).to.equal(1);
+        expect(db._getSnapshotOpLink.notCalled).to.equal(true);
+        expect(db._getOps.calledOnceWith(collection, id, 0, 2)).to.equal(true);
         done();
       });
     });
@@ -81,16 +81,16 @@ describe('getOpsWithoutStrictLinking: true', function() {
 
       callInSeries([
         function(next) {
-          mongo.collection('o_' + collection).insert(spuriousOp, next);
+          mongo.db().collection('o_' + collection).insertOne(spuriousOp, next);
         },
         function(result, next) {
           db.getOps(collection, id, 0, 2, null, next);
         },
         function(ops, next) {
-          expect(ops.length).to.be(2);
-          expect(ops[1].oi).to.be('bar');
-          expect(db._getSnapshotOpLink.notCalled).to.be(true);
-          expect(db._getOps.calledOnceWith(collection, id, 0, 2)).to.be(true);
+          expect(ops.length).to.equal(2);
+          expect(ops[1].oi).to.equal('bar');
+          expect(db._getSnapshotOpLink.notCalled).to.equal(true);
+          expect(db._getOps.calledOnceWith(collection, id, 0, 2)).to.equal(true);
           next();
         },
         done
@@ -102,16 +102,16 @@ describe('getOpsWithoutStrictLinking: true', function() {
 
       callInSeries([
         function(next) {
-          mongo.collection('o_' + collection).insert(spuriousOp, next);
+          mongo.db().collection('o_' + collection).insertOne(spuriousOp, next);
         },
         function(result, next) {
           db.getOps(collection, id, 0, 2, null, next);
         },
         function(ops, next) {
-          expect(ops.length).to.be(2);
-          expect(ops[1].oi).to.be('bar');
-          expect(db._getSnapshotOpLink.notCalled).to.be(true);
-          expect(db._getOps.calledOnceWith(collection, id, 0, 3)).to.be(true);
+          expect(ops.length).to.equal(2);
+          expect(ops[1].oi).to.equal('bar');
+          expect(db._getSnapshotOpLink.notCalled).to.equal(true);
+          expect(db._getOps.calledOnceWith(collection, id, 0, 3)).to.equal(true);
           next();
         },
         done
@@ -128,16 +128,16 @@ describe('getOpsWithoutStrictLinking: true', function() {
 
       callInSeries([
         function(next) {
-          mongo.collection('o_' + collection).insertMany(spuriousOps, next);
+          mongo.db().collection('o_' + collection).insertMany(spuriousOps, next);
         },
         function(result, next) {
           db.getOps(collection, id, 0, 2, null, next);
         },
         function(ops, next) {
-          expect(ops.length).to.be(2);
+          expect(ops.length).to.equal(2);
           expect(ops[0].create).to.eql({});
-          expect(ops[1].oi).to.be('bar');
-          expect(db._getSnapshotOpLink.calledOnce).to.be(true);
+          expect(ops[1].oi).to.equal('bar');
+          expect(db._getSnapshotOpLink.calledOnce).to.equal(true);
           next();
         },
         done
@@ -163,7 +163,7 @@ function commitOpChain(db, mongo, collection, id, ops, previousOpId, version, ca
   var snapshot = {id: id, v: version + 1, type: 'json0', data: {}, m: null, _opLink: previousOpId};
   db.commit(collection, id, op, snapshot, null, function(error) {
     if (error) return callback(error);
-    mongo.collection('o_' + collection).find({d: id, v: version}).next(function(error, op) {
+    mongo.db().collection('o_' + collection).find({d: id, v: version}).next(function(error, op) {
       if (error) return callback(error);
       commitOpChain(db, mongo, collection, id, ops, op._id, ++version, callback);
     });
diff --git a/test/test_mongo.js b/test/test_mongo.js
index 7a75c955..1de639cf 100644
--- a/test/test_mongo.js
+++ b/test/test_mongo.js
@@ -1,4 +1,4 @@
-var expect = require('expect.js');
+var expect = require('chai').expect;
 var mongodb = require('mongodb');
 var ShareDbMongo = require('../index');
 var getQuery = require('sharedb-mingo-memory/get-query');
@@ -9,7 +9,7 @@ function create(callback) {
   var db = new ShareDbMongo({mongo: function(shareDbCallback) {
     mongodb.connect(mongoUrl, function(err, mongo) {
       if (err) return callback(err);
-      mongo.dropDatabase(function(err) {
+      mongo.db().dropDatabase(function(err) {
         if (err) return callback(err);
         shareDbCallback(null, mongo);
         callback(null, db, mongo);
@@ -40,12 +40,12 @@ describe('mongo db', function() {
       var mongo = this.mongo;
       this.db.commit('testcollection', 'foo', {v: 0, create: {}}, {}, null, function(err) {
         if (err) return done(err);
-        mongo.collection('o_testcollection').indexInformation(function(err, indexes) {
+        mongo.db().collection('o_testcollection').indexInformation(function(err, indexes) {
           if (err) return done(err);
           // Index for getting document(s) ops
-          expect(indexes['d_1_v_1']).ok();
+          expect(indexes['d_1_v_1']).ok;
           // Index for checking committed op(s) by src and seq
-          expect(indexes['src_1_seq_1_v_1']).ok();
+          expect(indexes['src_1_seq_1_v_1']).ok;
           done();
         });
       });
@@ -53,7 +53,7 @@ describe('mongo db', function() {
 
     it('respects unique indexes', function(done) {
       var db = this.db;
-      this.mongo.collection('testcollection').createIndex({x: 1}, {unique: true}, function(err) {
+      this.mongo.db().collection('testcollection').createIndex({x: 1}, {unique: true}, function(err) {
         if (err) return done(err);
         db.commit('testcollection', 'foo', {v: 0, create: {}}, {v: 1, data: {x: 7}}, null, function(err) {
           if (err) return done(err);
@@ -70,9 +70,9 @@ describe('mongo db', function() {
     it('does not allow editing the system collection', function(done) {
       var db = this.db;
       db.commit('system', 'test', {v: 0, create: {}}, {}, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         db.getSnapshot('system', 'test', null, null, function(err) {
-          expect(err).ok();
+          expect(err).ok;
           done();
         });
       });
@@ -85,21 +85,21 @@ describe('mongo db', function() {
 
     it('does not allow $where queries', function(done) {
       this.db.query('testcollection', {$where: 'true'}, null, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         done();
       });
     });
 
     it('queryPollDoc does not allow $where queries', function(done) {
       this.db.queryPollDoc('testcollection', 'somedoc', {$where: 'true'}, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         done();
       });
     });
 
     it('$query is deprecated', function(done) {
       this.db.query('testcollection', {$query: {}}, null, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         expect(err.code).eql(4106);
         done();
       });
@@ -107,7 +107,7 @@ describe('mongo db', function() {
 
     it('only one collection operation allowed', function(done) {
       this.db.query('testcollection', {$distinct: {y: 1}, $aggregate: {}}, null, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         expect(err.code).eql(4108);
         done();
       });
@@ -115,7 +115,7 @@ describe('mongo db', function() {
 
     it('only one cursor operation allowed', function(done) {
       this.db.query('testcollection', {$count: true, $explain: true}, null, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         expect(err.code).eql(4109);
         done();
       });
@@ -123,7 +123,7 @@ describe('mongo db', function() {
 
     it('cursor transform can\'t run after collection operation', function(done) {
       this.db.query('testcollection', {$distinct: {y: 1}, $sort: {y: 1}}, null, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         expect(err.code).eql(4110);
         done();
       });
@@ -131,7 +131,7 @@ describe('mongo db', function() {
 
     it('cursor operation can\'t run after collection operation', function(done) {
       this.db.query('testcollection', {$distinct: {y: 1}, $count: true}, null, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         expect(err.code).eql(4110);
         done();
       });
@@ -139,7 +139,7 @@ describe('mongo db', function() {
 
     it('non-object $readPref should return error', function(done) {
       this.db.query('testcollection', {$readPref: true}, null, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         expect(err.code).eql(4107);
         done();
       });
@@ -148,7 +148,7 @@ describe('mongo db', function() {
     it('malformed $mapReduce should return error', function(done) {
       this.db.allowJSQueries = true; // required for $mapReduce
       this.db.query('testcollection', {$mapReduce: true}, null, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         expect(err.code).eql(4107);
         done();
       });
@@ -255,7 +255,7 @@ describe('mongo db', function() {
         {$sort: {count: 1}}
       ]};
       this.db.query('testcollection', query, null, null, function(err) {
-        expect(err).ok();
+        expect(err).ok;
         done();
       });
     });
@@ -286,7 +286,7 @@ describe('mongo db', function() {
               }
             };
             db.query('testcollection', query, null, null, function(err) {
-              expect(err).ok();
+              expect(err).ok;
               done();
             });
           });
@@ -341,7 +341,7 @@ describe('mongo db connection', function() {
       // logic.
       this.db.getDbs(function(err, mongo) {
         if (err) return done(err);
-        mongo.dropDatabase(function(err) {
+        mongo.db().dropDatabase(function(err) {
           if (err) return done(err);
           done();
         });
diff --git a/test/test_op_link_validator.js b/test/test_op_link_validator.js
index c2366aed..70aa8324 100644
--- a/test/test_op_link_validator.js
+++ b/test/test_op_link_validator.js
@@ -1,16 +1,16 @@
 var OpLinkValidator = require('../op-link-validator');
-var expect = require('expect.js');
+var expect = require('chai').expect;
 
 describe('OpLinkValidator', function() {
   it('starts with no unique op', function() {
     var validator = new OpLinkValidator();
     var opWithUniqueVersion = validator.opWithUniqueVersion();
-    expect(opWithUniqueVersion).to.be(null);
+    expect(opWithUniqueVersion).to.equal(null);
   });
 
   it('starts not at the end of the list', function() {
     var validator = new OpLinkValidator();
-    expect(validator.isAtEndOfList()).to.be(false);
+    expect(validator.isAtEndOfList()).to.equal(false);
   });
 
   it('has no unique op with just one op', function() {
@@ -20,7 +20,7 @@ describe('OpLinkValidator', function() {
     validator.push(op);
     var opWithUniqueVersion = validator.opWithUniqueVersion();
 
-    expect(opWithUniqueVersion).to.be(null);
+    expect(opWithUniqueVersion).to.equal(null);
   });
 
   it('has a unique op with just two different ops', function() {
@@ -32,7 +32,7 @@ describe('OpLinkValidator', function() {
     validator.push(op2);
     var opWithUniqueVersion = validator.opWithUniqueVersion();
 
-    expect(opWithUniqueVersion).to.be(op1);
+    expect(opWithUniqueVersion).to.equal(op1);
   });
 
   it('does not have a uniquye op with just two identical ops', function() {
@@ -44,7 +44,7 @@ describe('OpLinkValidator', function() {
     validator.push(op2);
     var opWithUniqueVersion = validator.opWithUniqueVersion();
 
-    expect(opWithUniqueVersion).to.be(null);
+    expect(opWithUniqueVersion).to.equal(null);
   });
 
   it('has a unique op with three ops with different versions', function() {
@@ -58,7 +58,7 @@ describe('OpLinkValidator', function() {
     validator.push(op3);
     var opWithUniqueVersion = validator.opWithUniqueVersion();
 
-    expect(opWithUniqueVersion).to.be(op2);
+    expect(opWithUniqueVersion).to.equal(op2);
   });
 
   it('is not at the end of the list with three ops', function() {
@@ -71,7 +71,7 @@ describe('OpLinkValidator', function() {
     validator.push(op2);
     validator.push(op3);
 
-    expect(validator.isAtEndOfList()).to.be(false);
+    expect(validator.isAtEndOfList()).to.equal(false);
   });
 
   it('does not have a unique op with three ops with the same version', function() {
@@ -83,7 +83,7 @@ describe('OpLinkValidator', function() {
     validator.push(op);
     var opWithUniqueVersion = validator.opWithUniqueVersion();
 
-    expect(opWithUniqueVersion).to.be(null);
+    expect(opWithUniqueVersion).to.equal(null);
   });
 
   it('does not have a unique op if the first two ops are the same', function() {
@@ -97,7 +97,7 @@ describe('OpLinkValidator', function() {
     validator.push(op3);
     var opWithUniqueVersion = validator.opWithUniqueVersion();
 
-    expect(opWithUniqueVersion).to.be(null);
+    expect(opWithUniqueVersion).to.equal(null);
   });
 
   it('does not have a unique op if the last two ops are the same', function() {
@@ -111,7 +111,7 @@ describe('OpLinkValidator', function() {
     validator.push(op3);
     var opWithUniqueVersion = validator.opWithUniqueVersion();
 
-    expect(opWithUniqueVersion).to.be(null);
+    expect(opWithUniqueVersion).to.equal(null);
   });
 
   it('has a unique op in a long chain', function() {
@@ -133,7 +133,7 @@ describe('OpLinkValidator', function() {
     validator.push(op7);
     var opWithUniqueVersion = validator.opWithUniqueVersion();
 
-    expect(opWithUniqueVersion).to.be(op6);
+    expect(opWithUniqueVersion).to.equal(op6);
   });
 
   it('has a unique op with two ops and a current op of null', function() {
@@ -147,13 +147,13 @@ describe('OpLinkValidator', function() {
     validator.push(op3);
     var opWithUniqueVersion = validator.opWithUniqueVersion();
 
-    expect(opWithUniqueVersion).to.be(op2);
+    expect(opWithUniqueVersion).to.equal(op2);
   });
 
   it('is at the end of the list with a current op of null', function() {
     var op = null;
     var validator = new OpLinkValidator();
     validator.push(op);
-    expect(validator.isAtEndOfList()).to.be(true);
+    expect(validator.isAtEndOfList()).to.equal(true);
   });
 });
diff --git a/test/test_skip_poll.js b/test/test_skip_poll.js
index fae3a679..587f4058 100644
--- a/test/test_skip_poll.js
+++ b/test/test_skip_poll.js
@@ -1,4 +1,4 @@
-var expect = require('expect.js');
+var expect = require('chai').expect;
 var ShareDbMongo = require('../index');
 
 describe('skipPoll', function() {