diff --git a/package.json b/package.json
index 9cfdb7c..967b78e 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,7 @@
     "pretests-only": "npm run build",
     "tests-only": "npm run test:quick",
     "precoverage": "npm run build",
-    "coverage": "babel-node node_modules/.bin/istanbul cover --report html node_modules/.bin/_mocha -- -R tap test/init.js test/*-test.js",
+    "coverage": "babel-node node_modules/.bin/istanbul cover --report html node_modules/.bin/_mocha -- -R tap test/init.js test/*-test.js test/**/*-test.js",
     "postcoverage": "npm run cover:check",
     "cover:check": "istanbul check-coverage && echo code coverage thresholds met, achievement unlocked!",
     "test:quick": "babel-node node_modules/.bin/_mocha -R tap test/init.js test/*-test.js"
diff --git a/src/environment.js b/src/environment.js
index 80ad23d..59e9936 100644
--- a/src/environment.js
+++ b/src/environment.js
@@ -1,26 +1,5 @@
 /* eslint func-names:0 no-extra-parens:0  */
 import 'airbnb-js-shims';
-import Promise from 'bluebird';
+import StrictPromise from './utils/strict-promise';
 
-const es6methods = ['then', 'catch', 'constructor'];
-const es6StaticMethods = ['all', 'race', 'resolve', 'reject', 'cast'];
-
-function isNotMethod(name) {
-  return !(es6methods.includes(name) || es6StaticMethods.includes(name) || name.charAt(0) === '_');
-}
-
-function del(obj) {
-  /* eslint no-param-reassign: 0 */
-  return (key) => { delete obj[key]; };
-}
-
-function toFastProperties(obj) {
-  (function () {}).prototype = obj;
-}
-
-Object.keys(Promise.prototype).filter(isNotMethod).forEach(del(Promise.prototype));
-Object.keys(Promise).filter(isNotMethod).forEach(del(Promise));
-toFastProperties(Promise);
-toFastProperties(Promise.prototype);
-
-global.Promise = Promise;
+global.Promise = StrictPromise;
diff --git a/src/utils/strict-promise.js b/src/utils/strict-promise.js
new file mode 100644
index 0000000..d0f567c
--- /dev/null
+++ b/src/utils/strict-promise.js
@@ -0,0 +1,69 @@
+/* eslint-disable no-underscore-dangle */
+
+import Promise from 'bluebird';
+
+export default class StrictPromise {
+  constructor(executor) {
+    this._promise = new Promise(executor);
+  }
+
+  static all(iterable) {
+    const newPromise = Promise.all(iterable);
+
+    const strictPromise = new StrictPromise((resolve, reject) => {
+      newPromise.then(resolve, reject);
+    });
+
+    return strictPromise;
+  }
+
+  static race(iterable) {
+    const newPromise = Promise.race(iterable);
+
+    const strictPromise = new StrictPromise((resolve, reject) => {
+      newPromise.then(resolve, reject);
+    });
+
+    return strictPromise;
+  }
+
+  static reject(value) {
+    const newPromise = Promise.reject(value);
+
+    const strictPromise = new StrictPromise((resolve, reject) => {
+      newPromise.then(resolve, reject);
+    });
+
+    return strictPromise;
+  }
+
+  static resolve(value) {
+    const newPromise = Promise.resolve(value);
+
+    const strictPromise = new StrictPromise((resolve, reject) => {
+      newPromise.then(resolve, reject);
+    });
+
+    return strictPromise;
+  }
+
+  then(onFulfilled, onRejected) {
+    const newPromise = this._promise.then(onFulfilled, onRejected);
+
+    const strictPromise = new StrictPromise((resolve, reject) => {
+      newPromise.then(resolve, reject);
+    });
+
+    return strictPromise;
+  }
+
+  catch(onRejected) {
+    const newPromise = this._promise.catch(onRejected);
+
+    const strictPromise = new StrictPromise((resolve, reject) => {
+      newPromise.then(resolve, reject);
+    });
+
+    return strictPromise;
+  }
+}
diff --git a/test/environment-test.js b/test/environment-test.js
new file mode 100644
index 0000000..21f1a9e
--- /dev/null
+++ b/test/environment-test.js
@@ -0,0 +1,19 @@
+import { assert } from 'chai';
+import '../src/environment';
+
+describe('environment', () => {
+  describe('global promise', () => {
+    it('has ES6 methods', () => {
+      assert.isFunction(global.Promise.prototype.then);
+      assert.isFunction(global.Promise.prototype.catch);
+      assert.isFunction(global.Promise.prototype.constructor);
+    });
+
+    it('has ES6 static methods', () => {
+      assert.isFunction(global.Promise.all);
+      assert.isFunction(global.Promise.race);
+      assert.isFunction(global.Promise.resolve);
+      assert.isFunction(global.Promise.reject);
+    });
+  });
+});
diff --git a/test/utils/strict-promise-test.js b/test/utils/strict-promise-test.js
new file mode 100644
index 0000000..41ebae7
--- /dev/null
+++ b/test/utils/strict-promise-test.js
@@ -0,0 +1,170 @@
+import { assert } from 'chai';
+import StrictPromise from '../../src/utils/strict-promise';
+
+describe('StrictPromise', () => {
+  describe('static all', () => {
+    it('resolves when the iterable is empty', (done) => {
+      StrictPromise.all([]).then(() => {
+        done();
+      });
+    });
+
+    it('resolves when the whole iterable is resolved', (done) => {
+      const resolveWiths = [];
+      const messages = [
+        'First resolved.',
+        'Second resolved.',
+        'Third resolved',
+      ];
+
+      StrictPromise.all([
+        new StrictPromise((resolve) => {
+          resolveWiths.push(resolve);
+        }),
+        new StrictPromise((resolve) => {
+          resolveWiths.push(resolve);
+        }),
+        new StrictPromise((resolve) => {
+          resolveWiths.push(resolve);
+        }),
+      ]).then((resolvedWiths) => {
+        assert.strictEqual(resolvedWiths[0], messages[0]);
+        assert.strictEqual(resolvedWiths[1], messages[1]);
+        assert.strictEqual(resolvedWiths[2], messages[2]);
+        done();
+      });
+
+      resolveWiths[0](messages[0]);
+      resolveWiths[1](messages[1]);
+      resolveWiths[2](messages[2]);
+    });
+
+    it('rejects with the first rejected iterable', (done) => {
+      let rejectWith;
+      const message = 'Only one rejected.';
+
+      StrictPromise.all([
+        new StrictPromise(() => {}),
+        new StrictPromise((resolve, reject) => {
+          rejectWith = reject;
+        }),
+        new StrictPromise(() => {}),
+      ]).then(() => {}, (rejectedWith) => {
+        assert.strictEqual(rejectedWith, message);
+        done();
+      });
+
+      rejectWith(message);
+    });
+  });
+
+  describe('static race', () => {
+    it('resolves with the first resolved iterable', (done) => {
+      let resolveWith;
+      const message = 'It is a resolved race!';
+
+      StrictPromise.race([
+        new StrictPromise(() => {}),
+        new StrictPromise((resolve) => {
+          resolveWith = resolve;
+        }),
+        new StrictPromise(() => {}),
+      ]).then((resolvedWith) => {
+        assert.strictEqual(resolvedWith, message);
+        done();
+      });
+
+      resolveWith(message);
+    });
+
+    it('rejects with the first rejected iterable', (done) => {
+      let rejectWith;
+      const message = 'It is a rejected race!';
+
+      StrictPromise.race([
+        new StrictPromise(() => {}),
+        new StrictPromise((resolve, reject) => {
+          rejectWith = reject;
+        }),
+        new StrictPromise(() => {}),
+      ]).then(() => {}, (rejectedWith) => {
+        assert.strictEqual(rejectedWith, message);
+        done();
+      });
+
+      rejectWith(message);
+    });
+  });
+
+  describe('static reject', () => {
+    it('rejects with a given reason', (done) => {
+      const message = 'rejected';
+
+      StrictPromise.reject(message).catch((rejectedWith) => {
+        assert.strictEqual(rejectedWith, message);
+        done();
+      });
+    });
+  });
+
+  describe('static resolve', () => {
+    it('resolves with a given reason', (done) => {
+      const message = 'fulfilled';
+
+      StrictPromise.resolve(message).then((resolvedWith) => {
+        assert.strictEqual(resolvedWith, message);
+        done();
+      });
+    });
+  });
+
+  describe('thennable', () => {
+    it('has a fulfillment callback', (done) => {
+      let resolveWith;
+      const message = 'fulfilled';
+
+      const promise = new StrictPromise((resolve) => {
+        resolveWith = resolve;
+      });
+
+      promise.then((resolvedWith) => {
+        assert.strictEqual(resolvedWith, message);
+        done();
+      });
+
+      resolveWith(message);
+    });
+
+    it('has a rejection callback', (done) => {
+      let rejectWith;
+      const message = 'rejected';
+
+      const promise = new StrictPromise((resolve, reject) => {
+        rejectWith = reject;
+      });
+
+      promise.then(() => {}, (rejectedWith) => {
+        assert.strictEqual(rejectedWith, message);
+        done();
+      });
+
+      rejectWith(message);
+    });
+  });
+
+  it('is catchable', (done) => {
+    let rejectWith;
+    const message = 'rejected';
+
+    const promise = new StrictPromise((resolve, reject) => {
+      rejectWith = reject;
+    });
+
+    promise.catch((rejectedWith) => {
+      assert.strictEqual(rejectedWith, message);
+      done();
+    });
+
+    rejectWith(message);
+  });
+});