diff --git a/test/built-ins/WeakRef/constructor.js b/test/built-ins/WeakRef/constructor.js
index 3dded764053..ff011555af3 100644
--- a/test/built-ins/WeakRef/constructor.js
+++ b/test/built-ins/WeakRef/constructor.js
@@ -10,5 +10,5 @@ description: >
 
 assert.sameValue(
   typeof WeakRef, 'function',
-  'typeof WeakRef is "function"'
+  'typeof WeakRef is 'function''
 );
diff --git a/test/built-ins/WeakRef/instance-extensible.js b/test/built-ins/WeakRef/instance-extensible.js
new file mode 100644
index 00000000000..d6249e22ee9
--- /dev/null
+++ b/test/built-ins/WeakRef/instance-extensible.js
@@ -0,0 +1,31 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-weak-ref-target
+description: Instances of WeakRef are extensible
+info: |
+  WeakRef( target )
+
+  ...
+  3. Let weakRef be ? OrdinaryCreateFromConstructor(NewTarget,  "%WeakRefPrototype%", « [[Target]] »).
+  4. Perfom ! KeepDuringJob(target).
+  5. Set weakRef.[[Target]] to target.
+  6. Return weakRef.
+
+  OrdinaryCreateFromConstructor ( constructor, intrinsicDefaultProto [ , internalSlotsList ] )
+
+  ...
+  2. Let proto be ? GetPrototypeFromConstructor(constructor, intrinsicDefaultProto).
+  3. Return ObjectCreate(proto, internalSlotsList).
+
+  ObjectCreate ( proto [ , internalSlotsList ] )
+
+  4. Set obj.[[Prototype]] to proto.
+  5. Set obj.[[Extensible]] to true.
+  6. Return obj.
+features: [WeakRef, Reflect]
+---*/
+
+var wr = new WeakRef({});
+assert.sameValue(Object.isExtensible(wr), true);
diff --git a/test/built-ins/WeakRef/length.js b/test/built-ins/WeakRef/length.js
index 472055c72eb..9ced86beb43 100644
--- a/test/built-ins/WeakRef/length.js
+++ b/test/built-ins/WeakRef/length.js
@@ -24,7 +24,7 @@ includes: [propertyHelper.js]
 features: [WeakRef]
 ---*/
 
-verifyProperty(WeakRef, "length", {
+verifyProperty(WeakRef, 'length', {
   value: 1,
   writable: false,
   enumerable: false,
diff --git a/test/built-ins/WeakRef/name.js b/test/built-ins/WeakRef/name.js
index f110f3e30a3..d47b73b5df0 100644
--- a/test/built-ins/WeakRef/name.js
+++ b/test/built-ins/WeakRef/name.js
@@ -23,8 +23,8 @@ includes: [propertyHelper.js]
 features: [WeakRef]
 ---*/
 
-verifyProperty(WeakRef, "name", {
-  value: "WeakRef",
+verifyProperty(WeakRef, 'name', {
+  value: 'WeakRef',
   writable: false,
   enumerable: false,
   configurable: true
diff --git a/test/built-ins/WeakRef/newtarget-prototype-is-not-object.js b/test/built-ins/WeakRef/newtarget-prototype-is-not-object.js
new file mode 100644
index 00000000000..d0ce62e86a3
--- /dev/null
+++ b/test/built-ins/WeakRef/newtarget-prototype-is-not-object.js
@@ -0,0 +1,58 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-weak-ref-target
+description: >
+  [[Prototype]] defaults to %WeakRefPrototype% if NewTarget.prototype is not an object.
+info: |
+  WeakRef( target )
+
+  ...
+  3. Let weakRef be ? OrdinaryCreateFromConstructor(NewTarget,  "%WeakRefPrototype%", « [[Target]] »).
+  4. Perfom ! KeepDuringJob(target).
+  5. Set weakRef.[[Target]] to target.
+  6. Return weakRef.
+
+  OrdinaryCreateFromConstructor ( constructor, intrinsicDefaultProto [ , internalSlotsList ] )
+
+  ...
+  2. Let proto be ? GetPrototypeFromConstructor(constructor, intrinsicDefaultProto).
+  3. Return ObjectCreate(proto, internalSlotsList).
+
+  GetPrototypeFromConstructor ( constructor, intrinsicDefaultProto )
+
+  3. Let proto be ? Get(constructor, 'prototype').
+  4. If Type(proto) is not Object, then
+    a. Let realm be ? GetFunctionRealm(constructor).
+    b. Set proto to realm's intrinsic object named intrinsicDefaultProto.
+  5. Return proto.
+features: [WeakRef, Reflect.construct, Symbol]
+---*/
+
+var WeakRef;
+function newTarget() {}
+
+newTarget.prototype = undefined;
+WeakRef = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(WeakRef), WeakRef.prototype, 'newTarget.prototype is undefined');
+
+newTarget.prototype = null;
+WeakRef = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(WeakRef), WeakRef.prototype, 'newTarget.prototype is null');
+
+newTarget.prototype = true;
+WeakRef = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(WeakRef), WeakRef.prototype, 'newTarget.prototype is a Boolean');
+
+newTarget.prototype = '';
+WeakRef = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(WeakRef), WeakRef.prototype, 'newTarget.prototype is a String');
+
+newTarget.prototype = Symbol();
+WeakRef = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(WeakRef), WeakRef.prototype, 'newTarget.prototype is a Symbol');
+
+newTarget.prototype = 1;
+WeakRef = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(WeakRef), WeakRef.prototype, 'newTarget.prototype is a Number');
diff --git a/test/built-ins/WeakRef/prop-desc.js b/test/built-ins/WeakRef/prop-desc.js
index 914d21c71e4..26a9b2933ef 100644
--- a/test/built-ins/WeakRef/prop-desc.js
+++ b/test/built-ins/WeakRef/prop-desc.js
@@ -15,7 +15,7 @@ includes: [propertyHelper.js]
 features: [WeakRef]
 ---*/
 
-verifyProperty(this, "WeakRef", {
+verifyProperty(this, 'WeakRef', {
   enumerable: false,
   writable: true,
   configurable: true
diff --git a/test/built-ins/WeakRef/proto-from-ctor-realm.js b/test/built-ins/WeakRef/proto-from-ctor-realm.js
new file mode 100644
index 00000000000..4345e095d14
--- /dev/null
+++ b/test/built-ins/WeakRef/proto-from-ctor-realm.js
@@ -0,0 +1,59 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-weak-ref-target
+description: Default [[Prototype]] value derived from realm of the newTarget
+info: |
+  WeakRef( target )
+
+  ...
+  3. Let weakRef be ? OrdinaryCreateFromConstructor(NewTarget,  '%WeakRefPrototype%', « [[Target]] »).
+  4. Perfom ! KeepDuringJob(target).
+  5. Set weakRef.[[Target]] to target.
+  6. Return weakRef.
+
+  OrdinaryCreateFromConstructor ( constructor, intrinsicDefaultProto [ , internalSlotsList ] )
+
+  ...
+  2. Let proto be ? GetPrototypeFromConstructor(constructor, intrinsicDefaultProto).
+  3. Return ObjectCreate(proto, internalSlotsList).
+
+  GetPrototypeFromConstructor ( constructor, intrinsicDefaultProto )
+
+  3. Let proto be ? Get(constructor, 'prototype').
+  4. If Type(proto) is not Object, then
+    a. Let realm be ? GetFunctionRealm(constructor).
+    b. Set proto to realm's intrinsic object named intrinsicDefaultProto.
+  5. Return proto.
+features: [WeakRef, cross-realm, Reflect]
+---*/
+
+var other = $262.createRealm().global;
+var newTarget = new other.Function();
+var wr;
+
+newTarget.prototype = undefined;
+wr = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(wr), other.WeakRef.prototype, 'newTarget.prototype is undefined');
+
+newTarget.prototype = null;
+wr = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(wr), other.WeakRef.prototype, 'newTarget.prototype is null');
+
+newTarget.prototype = true;
+wr = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(wr), other.WeakRef.prototype, 'newTarget.prototype is a Boolean');
+
+newTarget.prototype = '';
+wr = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(wr), other.WeakRef.prototype, 'newTarget.prototype is a String');
+
+newTarget.prototype = Symbol();
+wr = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(wr), other.WeakRef.prototype, 'newTarget.prototype is a Symbol');
+
+newTarget.prototype = 1;
+wr = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(wr), other.WeakRef.prototype, 'newTarget.prototype is a Number');
+
diff --git a/test/built-ins/WeakRef/prototype-from-newtarget-abrupt.js b/test/built-ins/WeakRef/prototype-from-newtarget-abrupt.js
new file mode 100644
index 00000000000..952b2afb8cb
--- /dev/null
+++ b/test/built-ins/WeakRef/prototype-from-newtarget-abrupt.js
@@ -0,0 +1,42 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-weak-ref-target
+description: >
+  Return abrupt from getting the NewTarget prototype
+info: |
+  WeakRef ( target )
+
+  ...
+  3. Let weakRef be ? OrdinaryCreateFromConstructor(NewTarget,  "%WeakRefPrototype%", « [[Target]] »).
+  4. Perfom ! KeepDuringJob(target).
+  5. Set weakRef.[[Target]] to target.
+  6. Return weakRef.
+
+  OrdinaryCreateFromConstructor ( constructor, intrinsicDefaultProto [ , internalSlotsList ] )
+
+  ...
+  2. Let proto be ? GetPrototypeFromConstructor(constructor, intrinsicDefaultProto).
+  3. Return ObjectCreate(proto, internalSlotsList).
+
+  GetPrototypeFromConstructor ( constructor, intrinsicDefaultProto )
+
+  3. Let proto be ? Get(constructor, 'prototype').
+features: [WeakRef, Reflect.construct]
+---*/
+
+var calls = 0;
+var newTarget = function() {}.bind(null);
+Object.defineProperty(newTarget, 'prototype', {
+  get: function() {
+    calls += 1;
+    throw new Test262Error();
+  }
+});
+
+assert.throws(Test262Error, function() {
+  Reflect.construct(WeakRef, [{}], newTarget);
+});
+
+assert.sameValue(calls, 1);
\ No newline at end of file
diff --git a/test/built-ins/WeakRef/prototype-from-newtarget-custom.js b/test/built-ins/WeakRef/prototype-from-newtarget-custom.js
new file mode 100644
index 00000000000..104781f5074
--- /dev/null
+++ b/test/built-ins/WeakRef/prototype-from-newtarget-custom.js
@@ -0,0 +1,45 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-weak-ref-target
+description: >
+  The [[Prototype]] internal slot is computed from NewTarget.
+info: |
+  WeakRef ( target )
+
+  ...
+  3. Let weakRef be ? OrdinaryCreateFromConstructor(NewTarget,  "%WeakRefPrototype%", « [[Target]] »).
+  4. Perfom ! KeepDuringJob(target).
+  5. Set weakRef.[[Target]] to target.
+  6. Return weakRef.
+
+  OrdinaryCreateFromConstructor ( constructor, intrinsicDefaultProto [ , internalSlotsList ] )
+
+  ...
+  2. Let proto be ? GetPrototypeFromConstructor(constructor, intrinsicDefaultProto).
+  3. Return ObjectCreate(proto, internalSlotsList).
+
+  GetPrototypeFromConstructor ( constructor, intrinsicDefaultProto )
+
+  3. Let proto be ? Get(constructor, 'prototype').
+  4. If Type(proto) is not Object, then
+    a. Let realm be ? GetFunctionRealm(constructor).
+    b. Set proto to realm's intrinsic object named intrinsicDefaultProto.
+  5. Return proto.
+features: [WeakRef, Reflect.construct]
+---*/
+
+var wr;
+
+wr = Reflect.construct(WeakRef, [{}], Object);
+assert.sameValue(Object.getPrototypeOf(wr), Object.prototype, 'NewTarget is built-in Object constructor');
+
+var newTarget = function() {}.bind(null);
+Object.defineProperty(newTarget, 'prototype', {
+  get: function() {
+    return Array.prototype;
+  }
+});
+wr = Reflect.construct(WeakRef, [{}], newTarget);
+assert.sameValue(Object.getPrototypeOf(wr), Array.prototype, 'NewTarget is BoundFunction with accessor');
diff --git a/test/built-ins/WeakRef/prototype-from-newtarget.js b/test/built-ins/WeakRef/prototype-from-newtarget.js
new file mode 100644
index 00000000000..e7aa89dba19
--- /dev/null
+++ b/test/built-ins/WeakRef/prototype-from-newtarget.js
@@ -0,0 +1,34 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-weak-ref-target
+description: >
+  The [[Prototype]] internal slot is computed from NewTarget.
+info: |
+  WeakRef ( target )
+
+  ...
+  3. Let weakRef be ? OrdinaryCreateFromConstructor(NewTarget,  "%WeakRefPrototype%", « [[Target]] »).
+  4. Perfom ! KeepDuringJob(target).
+  5. Set weakRef.[[Target]] to target.
+  6. Return weakRef.
+
+  OrdinaryCreateFromConstructor ( constructor, intrinsicDefaultProto [ , internalSlotsList ] )
+
+  ...
+  2. Let proto be ? GetPrototypeFromConstructor(constructor, intrinsicDefaultProto).
+  3. Return ObjectCreate(proto, internalSlotsList).
+
+  GetPrototypeFromConstructor ( constructor, intrinsicDefaultProto )
+
+  3. Let proto be ? Get(constructor, 'prototype').
+  4. If Type(proto) is not Object, then
+    a. Let realm be ? GetFunctionRealm(constructor).
+    b. Set proto to realm's intrinsic object named intrinsicDefaultProto.
+  5. Return proto.
+features: [WeakRef]
+---*/
+
+var wr = new WeakRef({});
+assert.sameValue(Object.getPrototypeOf(wr), WeakRef.prototype);
diff --git a/test/built-ins/WeakRef/prototype/Symbol.toStringTag.js b/test/built-ins/WeakRef/prototype/Symbol.toStringTag.js
index a24705f739a..a6d4e11d865 100644
--- a/test/built-ins/WeakRef/prototype/Symbol.toStringTag.js
+++ b/test/built-ins/WeakRef/prototype/Symbol.toStringTag.js
@@ -7,7 +7,7 @@ description: >
     `Symbol.toStringTag` property descriptor
 info: |
     The initial value of the @@toStringTag property is the String value
-    "WeakRef".
+    'WeakRef'.
 
     This property has the attributes { [[Writable]]: false, [[Enumerable]]:
     false, [[Configurable]]: true }.
@@ -16,7 +16,7 @@ features: [WeakRef, Symbol, Symbol.toStringTag]
 ---*/
 
 verifyProperty(WeakRef.prototype, Symbol.toStringTag, {
-  value: "WeakRef",
+  value: 'WeakRef',
   writable: false,
   enumerable: false,
   configurable: true
diff --git a/test/built-ins/WeakRef/prototype/prop-desc.js b/test/built-ins/WeakRef/prototype/prop-desc.js
index 0a1f185aa73..8f4bacc735a 100644
--- a/test/built-ins/WeakRef/prototype/prop-desc.js
+++ b/test/built-ins/WeakRef/prototype/prop-desc.js
@@ -11,7 +11,7 @@ features: [WeakRef]
 includes: [propertyHelper.js]
 ---*/
 
-verifyProperty(WeakRef, "prototype", {
+verifyProperty(WeakRef, 'prototype', {
   writable: false,
   enumerable: false,
   configurable: false
diff --git a/test/built-ins/WeakRef/target-not-object-throws.js b/test/built-ins/WeakRef/target-not-object-throws.js
new file mode 100644
index 00000000000..9066effe57e
--- /dev/null
+++ b/test/built-ins/WeakRef/target-not-object-throws.js
@@ -0,0 +1,53 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-weak-ref-target
+description: >
+  Throws a TypeError if target is not Object
+info: |
+  WeakRef ( target )
+
+  1. If NewTarget is undefined, throw a TypeError exception.
+  2. If Type(target) is not Object, throw a TypeError exception.
+  ...
+features: [WeakRef]
+---*/
+
+assert.sameValue(
+  typeof WeakRef, 'function',
+  'typeof WeakRef is 'function''
+);
+
+assert.throws(TypeError, function() {
+  new WeakRef();
+}, 'implicit undefined');
+
+assert.throws(TypeError, function() {
+  new WeakRef(undefined);
+}, 'explicit undefined');
+
+assert.throws(TypeError, function() {
+  new WeakRef(null);
+}, 'null');
+
+assert.throws(TypeError, function() {
+  new WeakRef(1);
+}, 'number');
+
+assert.throws(TypeError, function() {
+  new WeakRef('Object');
+}, 'string');
+
+var s = Symbol();
+assert.throws(TypeError, function() {
+  new WeakRef(s);
+}, 'symbol');
+
+assert.throws(TypeError, function() {
+  new WeakRef(true);
+}, 'Boolean, true');
+
+assert.throws(TypeError, function() {
+  new WeakRef(false);
+}, 'Boolean, false');
diff --git a/test/built-ins/WeakRef/undefined-newtarget-throws.js b/test/built-ins/WeakRef/undefined-newtarget-throws.js
new file mode 100644
index 00000000000..6606e7afb37
--- /dev/null
+++ b/test/built-ins/WeakRef/undefined-newtarget-throws.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-weak-ref-target
+description: >
+  Throws a TypeError if NewTarget is undefined.
+info: |
+  WeakRef ( target )
+
+  1. If NewTarget is undefined, throw a TypeError exception.
+  2. If Type(target) is not Object, throw a TypeError exception.
+  ...
+features: [WeakRef]
+---*/
+
+assert.sameValue(
+  typeof WeakRef, 'function',
+  'typeof WeakRef is 'function''
+);
+
+assert.throws(TypeError, function() {
+  WeakRef();
+});
+
+assert.throws(TypeError, function() {
+  WeakRef({});
+});