diff --git a/types/es6-shim/es6-shim-tests.ts b/types/es6-shim/es6-shim-tests.ts
index ed89d2ac35..8f187e4d2b 100644
--- a/types/es6-shim/es6-shim-tests.ts
+++ b/types/es6-shim/es6-shim-tests.ts
@@ -1,31 +1,37 @@
-
+declare const require: (module: string) => Object;
+if (require !== null) {
+  require('es6-shim');
+}
 
 interface Point { x: number; y: number; }
 interface Point3D extends Point { z: number; }
 
 let a: any;
-let s: string;
-let i: number;
+let s: string = '';
+let i: number = 2;
+let iOrUndef: number | undefined;
 let b: boolean;
-let f: () => void;
+let f: () => void = () => {};
 let o: Object;
-let r: RegExp;
-let sym: symbol;
-let e: Error;
+let r: RegExp = /a/;
+let sym: symbol = {} as symbol;
+let e: Error = new Error();
 let date: Date;
 let key: PropertyKey;
-let point: Point;
-let point3d: Point3D;
-let arrayOfPoint: Point[];
+let point: Point = { x: 1, y: 2 };
+let point3d: Point3D = { x: 1, y: 2, z: 3 };
+let point3dOrUndef: Point3D | undefined;
+let pointOrUndef: Point | undefined;
+let arrayOfPoint: Point[] = [];
 let arrayOfPoint3D: Point3D[];
 let arrayOfSymbol: symbol[];
 let arrayOfPropertyKey: PropertyKey[];
 let arrayOfAny: any[];
 let arrayOfStringAny: [string, any][];
-let arrayLikeOfAny: ArrayLike<any>;
-let iterableOfPoint: IterableShim<Point>;
-let iterableOfStringPoint: IterableShim<[string, Point]>;
-let iterableOfPointPoint3D: IterableShim<[Point, Point3D]>;
+let arrayLikeOfAny: ArrayLike<any> = [];
+let iterableOfPoint: IterableShim<Point> = [];
+let iterableOfStringPoint: IterableShim<[string, Point]> = [];
+let iterableOfPointPoint3D: IterableShim<[Point, Point3D]> = [];
 let iterableIteratorOfPoint: IterableIteratorShim<Point>;
 let iterableIteratorOfNumberPoint: IterableIteratorShim<[number, Point]>;
 let iterableIteratorOfNumber: IterableIteratorShim<number>;
@@ -37,23 +43,23 @@ let iterableIteratorOfAny: IterableIteratorShim<any>;
 let iterableIteratorOfPropertyKey: IterableIteratorShim<PropertyKey>;
 let iterableIteratorOfPropertyKeyPoint: IterableIteratorShim<[PropertyKey, Point]>;
 let nodeList: NodeList;
-let pd: PropertyDescriptor;
-let pdm: PropertyDescriptorMap;
-let map: Map<string, Point>;
-let set: Set<Point>;
-let weakMap: WeakMap<Point, Point3D>;
-let weakSet: WeakSet<Point>;
-let promiseLikeOfPoint: PromiseLike<Point>;
-let promiseLikeOfPoint3D: PromiseLike<Point3D>;
-let promiseOfPoint: Promise<Point>;
-let promiseOfPoint3D: Promise<Point3D>;
+let pd: PropertyDescriptor = {};
+let pdm: PropertyDescriptorMap = {};
+let map: Map<string, Point> = new Map<string, Point>();
+let set: Set<Point> = new Set<Point>();
+let weakMap: WeakMap<Point, Point3D> = new WeakMap<Point, Point3D>();
+let weakSet: WeakSet<Point> = new WeakSet<Point>();
+let promiseLikeOfPoint: PromiseLike<Point> = Promise.resolve(point);
+let promiseLikeOfPoint3D: PromiseLike<Point3D> = Promise.resolve(point3d);
+let promiseOfPoint: Promise<Point> = Promise.resolve(point);
+let promiseOfPoint3D: Promise<Point3D> = Promise.resolve(point);
 let promiseOfArrayOfPoint: Promise<Point[]>;
 let promiseOfVoid: Promise<void>;
 
 point = Object.assign(point, point);
 b = Object.is(point, point);
-Object.setPrototypeOf(point, point);
-point = arrayOfPoint.find(p => b);
+Object.setPrototypeOf(point, {});
+pointOrUndef = arrayOfPoint.find(p => b);
 i = arrayOfPoint.findIndex(p => b);
 arrayOfPoint = arrayOfPoint.fill(point, i, arrayOfPoint.length);
 arrayOfPoint = arrayOfPoint.copyWithin(i, i, i);
@@ -69,7 +75,7 @@ b = s.includes(s, i);
 b = s.endsWith(s, i);
 s = s.repeat(i);
 b = s.startsWith(s, i);
-s = String.fromCodePoint(i, i);
+s = String.fromCodePoint(2 as number, 3 as number);
 s = String.raw`abc`;
 s = r.flags;
 i = Number.EPSILON;
@@ -102,7 +108,7 @@ i = Math.cbrt(i);
 map.clear();
 map.delete(s);
 map.forEach((value: Point, key: string) => { });
-point = map.get(s);
+pointOrUndef = map.get(s);
 b = map.has(s);
 map = map.set(s, point);
 i = map.size;
@@ -117,7 +123,7 @@ i = set.size;
 set = new Set<Point>();
 set = new Set(iterableOfPoint);
 weakMap.delete(point);
-point3d = weakMap.get(point);
+point3dOrUndef = weakMap.get(point);
 b = weakMap.has(point);
 weakMap = weakMap.set(point, point3d);
 weakMap = new WeakMap<Point, Point3D>();
@@ -184,6 +190,8 @@ promiseOfPoint = new Promise<Point>((resolve, reject) => resolve(point));
 promiseOfPoint = new Promise<Point>((resolve, reject) => resolve(promiseOfPoint));
 promiseOfPoint = new Promise<Point>((resolve, reject) => resolve(promiseLikeOfPoint));
 promiseOfPoint = new Promise<Point>((resolve, reject) => reject(e));
+// To prevent UnhandledPromiseRejectionWarning
+promiseOfPoint.catch(() => {});
 promiseOfArrayOfPoint = Promise.all(arrayOfPoint);
 promiseOfArrayOfPoint = Promise.all(iterableOfPoint);
 promiseOfPoint = Promise.race(arrayOfPoint);
@@ -193,7 +201,11 @@ promiseOfPoint = Promise.resolve(point3d);
 promiseOfPoint = Promise.resolve(promiseOfPoint);
 promiseOfPoint = Promise.resolve(promiseLikeOfPoint);
 promiseOfVoid = Promise.reject(e);
+// To prevent UnhandledPromiseRejectionWarning
+promiseOfVoid.catch(() => {});
 promiseOfPoint = Promise.reject<Point>(e);
+// To prevent UnhandledPromiseRejectionWarning
+promiseOfPoint.catch(() => {});
 a = Reflect.apply(f, a, arrayLikeOfAny);
 a = Reflect.construct(f, arrayLikeOfAny);
 b = Reflect.defineProperty(a, s, pd);
@@ -203,9 +215,9 @@ b = Reflect.deleteProperty(a, s);
 b = Reflect.deleteProperty(a, i);
 b = Reflect.deleteProperty(a, sym);
 iterableIteratorOfAny = Reflect.enumerate(a);
-a = Reflect.get(a, s, a);
-a = Reflect.get(a, i, a);
-a = Reflect.get(a, sym, a);
+Reflect.get(a, s, a);
+Reflect.get(a, i, a);
+Reflect.get(a, sym, a);
 pd = Reflect.getOwnPropertyDescriptor(a, s);
 pd = Reflect.getOwnPropertyDescriptor(a, i);
 pd = Reflect.getOwnPropertyDescriptor(a, sym);
@@ -219,4 +231,4 @@ b = Reflect.preventExtensions(a);
 b = Reflect.set(a, s, a, a);
 b = Reflect.set(a, i, a, a);
 b = Reflect.set(a, sym, a, a);
-b = Reflect.setPrototypeOf(a, a);
\ No newline at end of file
+b = Reflect.setPrototypeOf(a, a);
diff --git a/types/es6-shim/index.d.ts b/types/es6-shim/index.d.ts
index 483f4357e0..4c03fc8b9e 100644
--- a/types/es6-shim/index.d.ts
+++ b/types/es6-shim/index.d.ts
@@ -185,11 +185,10 @@ interface Array<T> {
       * @param thisArg If provided, it will be used as the this value for each invocation of
       * predicate. If it is not provided, undefined is used instead.
       */
-    find(predicate: (value: T, index: number, obj: Array<T>) => boolean, thisArg?: any): T;
+    find(predicate: (value: T, index: number, obj: Array<T>) => boolean, thisArg?: any): T | undefined;
 
     /**
-      * Returns the index of the first element in the array where predicate is true, and undefined
-      * otherwise.
+      * Returns the index of the first element in the array where predicate is true, and -1 otherwise.
       * @param predicate find calls predicate once for each element of the array, in ascending
       * order, until it finds one where predicate returns true. If such an element is found, find
       * immediately returns that element value. Otherwise, find returns undefined.
@@ -556,9 +555,9 @@ interface Map<K, V> {
     clear(): void;
     delete(key: K): boolean;
     forEach(callbackfn: (value: V, index: K, map: Map<K, V>) => void, thisArg?: any): void;
-    get(key: K): V;
+    get(key: K): V | undefined;
     has(key: K): boolean;
-    set(key: K, value?: V): Map<K, V>;
+    set(key: K, value: V): Map<K, V>;
     size: number;
     entries(): IterableIteratorShim<[K, V]>;
     keys(): IterableIteratorShim<K>;
@@ -596,9 +595,9 @@ declare var Set: SetConstructor;
 
 interface WeakMap<K extends object, V> {
     delete(key: K): boolean;
-    get(key: K): V;
+    get(key: K): V | undefined;
     has(key: K): boolean;
-    set(key: K, value?: V): WeakMap<K, V>;
+    set(key: K, value: V): WeakMap<K, V>;
 }
 
 interface WeakMapConstructor {
diff --git a/types/es6-shim/tsconfig.json b/types/es6-shim/tsconfig.json
index 1243a36ddb..02c35aee5a 100644
--- a/types/es6-shim/tsconfig.json
+++ b/types/es6-shim/tsconfig.json
@@ -7,7 +7,7 @@
         ],
         "noImplicitAny": true,
         "noImplicitThis": true,
-        "strictNullChecks": false,
+        "strictNullChecks": true,
         "baseUrl": "../",
         "typeRoots": [
             "../"
@@ -20,4 +20,4 @@
         "index.d.ts",
         "es6-shim-tests.ts"
     ]
-}
\ No newline at end of file
+}