diff --git a/lib/test.js b/lib/test.js
index da8dd3cf..4c79f0b3 100644
--- a/lib/test.js
+++ b/lib/test.js
@@ -79,8 +79,8 @@ Test.prototype.serverAddress = function(app, path) {
  */
 
 Test.prototype.expect = function(a, b, c) {
-  // callback
-  if (typeof a === 'function') {
+  // callback or promise
+  if (typeof a === 'function' || typeof a.then === 'function') {
     this._asserts.push(a);
     return this;
   }
@@ -145,7 +145,7 @@ Test.prototype.end = function(fn) {
  */
 
 Test.prototype.assert = function(resError, res, fn) {
-  var error;
+  var maybePromise;
   var i;
 
   // check for unexpected network errors or server not running/reachable errors
@@ -161,22 +161,58 @@ Test.prototype.assert = function(resError, res, fn) {
 
   if (!res && resError && (resError instanceof Error) && (resError.syscall === 'connect')
       && (Object.getOwnPropertyNames(sysErrors).indexOf(resError.code) >= 0)) {
-    error = new Error(resError.code + ': ' + sysErrors[resError.code]);
-    fn.call(this, error, null);
+    fn.call(
+      this,
+      new Error(resError.code + ': ' + sysErrors[resError.code]),
+      null
+    );
     return;
   }
 
   // asserts
-  for (i = 0; i < this._asserts.length && !error; i += 1) {
-    error = this._assertFunction(this._asserts[i], res);
+  for (i = 0; i < this._asserts.length; i += 1) {
+    // handle promises.
+    if (typeof this._asserts[i].then === 'function') {
+      this._asserts[i]
+        .then(res)
+        .catch(function(promiseError) {
+          return fn.call(this, promiseError, res);
+        })
+        .then(function(maybeError) {
+          if (maybeError instanceof Error) {
+            return fn.call(this, maybeError, res);
+          }
+        });
+      return;
+    }
+
+    // handle functions
+    maybePromise = this._assertFunction(this._asserts[i], res);
+    if (maybePromise && typeof maybePromise.then === 'function') {
+      // function returned a promise
+      maybePromise
+      .then(function(maybeError) { // eslint-disable-line no-loop-func
+        if (maybeError instanceof Error) {
+          return fn.call(this, maybeError, res);
+        }
+      })
+      .catch(function(promiseError) {
+        return fn.call(this, promiseError, res);
+      });
+      return;
+    } else if (maybePromise instanceof Error) {
+      // function returned a non-promise. if it is an error, report it.
+      return fn.call(this, maybePromise, res);
+    }
   }
 
   // set unexpected superagent error if no other error has occurred.
-  if (!error && resError instanceof Error && (!res || resError.status !== res.status)) {
-    error = resError;
+  if (resError instanceof Error && (!res || resError.status !== res.status)) {
+    return fn.call(this, resError, res);
   }
 
-  fn.call(this, error || null, res);
+  // no error
+  fn.call(this, null, res);
 };
 
 /**
@@ -282,7 +318,17 @@ Test.prototype._assertFunction = function(check, res) {
   } catch (e) {
     err = e;
   }
-  if (err instanceof Error) return err;
+
+  // We got an error, return it.
+  if (err instanceof Error) {
+    return err;
+  }
+
+  // We got a promise, return it and let the caller figure out if it contains
+  // an error.
+  if (err && typeof err.then === 'function') {
+    return err;
+  }
 };
 
 /**
diff --git a/package.json b/package.json
index 20984045..a5c48dc9 100644
--- a/package.json
+++ b/package.json
@@ -12,6 +12,7 @@
     "methods": "~1.1.2"
   },
   "devDependencies": {
+    "bluebird": "^3.4.7",
     "body-parser": "~1.16.0",
     "cookie-parser": "~1.4.1",
     "eslint": "^3.14.1",
@@ -21,6 +22,7 @@
     "eslint-plugin-react": "6.4.1",
     "express": "~4.14.0",
     "mocha": "~3.2.0",
+    "native-or-bluebird": "^1.2.0",
     "should": "~11.2.0"
   },
   "engines": {
diff --git a/test/supertest.js b/test/supertest.js
index c9a4927b..a61509c2 100644
--- a/test/supertest.js
+++ b/test/supertest.js
@@ -6,6 +6,7 @@ var should = require('should');
 var express = require('express');
 var bodyParser = require('body-parser');
 var cookieParser = require('cookie-parser');
+var Promise = require('native-or-bluebird');
 
 process.env.NODE_TLS_REJECT_UNAUTHORIZED = '0';
 
@@ -342,6 +343,100 @@ describe('request(app)', function() {
     });
   });
 
+  describe('.expect(fn)', function() {
+    it('should handle a function', function() {
+      var myFunction = function(res) {
+        res.text.should.equal('not hey');
+      };
+      var app = express();
+
+      app.get('/', function(req, res) {
+        res.send('hey');
+      });
+
+      return request(app)
+        .get('/')
+        .expect(200)
+        .expect(myFunction)
+        .then(function(res) {
+          throw new Error('Test passed.');
+        })
+        .catch(function(err) {
+          err.message.should.equal('expected \'hey\' to be \'not hey\'');
+        });
+    });
+
+    it('should handle function returning a promise', function() {
+      var myFunction = function(res) {
+        return new Promise(function(resolve, reject) {
+          reject(new Error('rejected'));
+        });
+      };
+      var app = express();
+
+      app.get('/', function(req, res) {
+        res.send('hey');
+      });
+
+      return request(app)
+        .get('/')
+        .expect(200)
+        .expect(myFunction)
+        .then(function(res) {
+          throw new Error('Test passed.');
+        })
+        .catch(function(err) {
+          err.message.should.equal('rejected');
+        });
+    });
+
+    it('should handle promises with callback resolution', function(done) {
+      Promise.resolve(function(res) {
+        res.text.should.equal('hey');
+        throw new Error('Promise threw.');
+      }).then(function(myPromise) {
+        var app = express();
+
+        app.get('/', function(req, res) {
+          res.send('hey');
+        });
+
+        request(app)
+          .get('/')
+          .expect(200)
+          .expect(myPromise)
+          .end(function(err, res) {
+            err.message.should.equal('Promise threw.');
+            done();
+          });
+      });
+    });
+
+    it('should handle promises with promise resolution', function() {
+      return Promise.resolve(function(res) {
+        res.text.should.equal('hey');
+        throw new Error('Promise threw.');
+      }).then(function(myPromise) {
+        var app = express();
+
+        app.get('/', function(req, res) {
+          res.send('hey');
+        });
+
+        return request(app)
+          .get('/')
+          .expect(200)
+          .expect(myPromise)
+          .then(function(res) {
+            throw new Error('Test passed.');
+          })
+          .catch(function(err) {
+            err.message.should.equal('Promise threw.');
+          });
+      });
+    });
+  });
+
   describe('.expect(status[, fn])', function() {
     it('should assert the response status', function(done) {
       var app = express();