diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-cannot-convert-to-primitive-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-cannot-convert-to-primitive-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..4aebe84585970dde6283d7073fe5103c5e4523ed
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-cannot-convert-to-primitive-err.js
@@ -0,0 +1,57 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  This value is an object which cannot be converted to a primitive
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+      b. If IsCallable(method) is true, then
+        i. Let result be ? Call(method, O).
+        ii. If Type(result) is not Object, return result.
+    6. Throw a TypeError exception.
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var thisVal = {
+  [Symbol.toPrimitive]: undefined,
+  toString: undefined,
+  valueOf: undefined,
+};
+
+// If trimEnd is called on an object with neither Symbol.toPrimitive, toString
+// nor valueOf defined, then a TypeError exception should be thrown.
+assert.throws(
+  TypeError,
+  function() { String.prototype.trimEnd.call(thisVal); },
+);
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-call-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-call-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..7ef1a2c1fbc2f0507e28cd92521cd0847658063b
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-call-err.js
@@ -0,0 +1,34 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Abrupt completion when getting Symbol.toPrimitive method
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive).
+   ...
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var thisVal = {
+  get [Symbol.toPrimitive]() {
+    throw new Test262Error();
+  },
+};
+
+assert.throws(Test262Error, function() {
+  String.prototype.trimEnd.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-meth-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-meth-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..f0bb5bf48be870fcf22f09b971109548b6281716
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-meth-err.js
@@ -0,0 +1,36 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+    Abrupt completion when Symbol.toPrimitive abrupt completes.
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive).
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+   ...
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var thisVal = {
+  [Symbol.toPrimitive]: function() {
+    throw new Test262Error();
+  },
+};
+
+assert.throws(Test262Error, function() {
+  String.prototype.trimEnd.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-meth-priority.js b/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-meth-priority.js
new file mode 100644
index 0000000000000000000000000000000000000000..df52f8a248149ae9b1d71a953ef883e7ab75b8ab
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-meth-priority.js
@@ -0,0 +1,74 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Priority of Symbol[toPrimitive] when converting object to string for trimming
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+   ...
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+
+var toPrimitiveAccessed = 0;
+var toStringAccessed = 0;
+var valueOfAccessed = 0;
+var thisVal = {
+  get [Symbol.toPrimitive]() {
+    toPrimitiveAccessed += 1;
+    return function() { return '42 '; };
+  },
+  get toString() {
+    toStringAccessed += 1;
+    return function() { return ''; };
+  },
+  get valueOf() {
+    valueOfAccessed += 1;
+    return function() { return ''; };
+  },
+};
+
+// Test that thisVal[Symbol.toPrimitive] has been called.
+
+var result = String.prototype.trimEnd.call(thisVal);
+
+assert.sameValue(
+  toPrimitiveAccessed,
+  1,
+  'thisVal[Symbol.toPrimitive] expected to have been accessed.'
+);
+assert.sameValue(
+  result,
+  '42',
+  'thisVal[Symbol.toPrimitive] expected to have been called.',
+);
+
+// Test that thisVal.toString and thisVal.valueOf have not been accessedo
+
+assert.sameValue(
+  toStringAccessed,
+  0,
+  'thisVal.toString should not have been accessed.'
+);
+assert.sameValue(
+  valueOfAccessed,
+  0,
+  'thisVal.valueOf should not have been accessed.'
+);
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-returns-object-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-returns-object-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..b67fe117a45f604016e40da3e7a6aa1b342f8c59
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-toprimitive-returns-object-err.js
@@ -0,0 +1,38 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+    Abrupt completion when Symbol.toPrimitive returns an object
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If arguement is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive).
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+   ...
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var thisVal = {
+  [Symbol.toPrimitive]: function() {
+    return {};
+  },
+};
+
+assert.throws(TypeError, function() {
+  String.prototype.trimEnd.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-call-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-call-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..f7ed44d1011aa998fbec4b7a6a5b5be74976fe30
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-call-err.js
@@ -0,0 +1,51 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Abrupt completion when getting toString method
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var thisVal = {
+  [Symbol.toPrimitive]: undefined,
+  get toString() {
+    throw new Test262Error();
+  },
+};
+
+assert.throws(Test262Error, function() {
+  String.prototype.trimEnd.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-meth-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-meth-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..40c2b9bcce2b1b4dd6d48ab45f325d7c892190b0
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-meth-err.js
@@ -0,0 +1,53 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Abrupt completion when toString called and abrupt completes.
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+      b. If IsCallable(method) is true, then
+        i. Let result be ? Call(method, O).
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var thisVal = {
+  [Symbol.toPrimitive]: undefined,
+  toString: function() {
+    throw new Test262Error();
+  },
+};
+
+assert.throws(Test262Error, function() {
+  String.prototype.trimEnd.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-meth-priority.js b/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-meth-priority.js
new file mode 100644
index 0000000000000000000000000000000000000000..06d82538fe809ea304fa3027c813c98bb67886e9
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-meth-priority.js
@@ -0,0 +1,93 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Priority of toString when converting object to string for trimming
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+      b. If IsCallable(method) is true, then
+        i. Let result be ? Call(method, O).
+        ii. If Type(result) is not Object, return result.
+   ...
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var toPrimitiveAccessed = 0;
+var toStringAccessed = 0;
+var valueOfAccessed = 0;
+var thisVal = {
+  get [Symbol.toPrimitive]() {
+    toPrimitiveAccessed +=1;
+    return undefined;
+  },
+  get toString() {
+    toStringAccessed += 1;
+    return function() { return '42 '; };
+  },
+  get valueOf() {
+    valueOfAccessed += 1;
+    return function() { return ''; };
+  },
+};
+
+// Test that toString is called when Symbol.toPrimitive is undefined.
+
+var result = String.prototype.trimEnd.call(thisVal)
+
+assert.sameValue(
+  toPrimitiveAccessed,
+  1,
+  'thisVal.toString expected to have been accessed.'
+);
+assert.sameValue(
+  result,
+  '42',
+  'thisVal.toString expected to have been called.',
+);
+
+// Test that thisVal[toPrimitive] has been accessed.
+
+assert.sameValue(
+  toPrimitiveAccessed,
+  1,
+  'thisVal[Symbol.toPrimitive should have been accessed.'
+);
+
+// Test that thisVal.valueOf has not been accessed.
+
+assert.sameValue(
+  valueOfAccessed,
+  0,
+  'thisVal.valueOf should not have been accessed.'
+);
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-returns-object-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-returns-object-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..e47539fadf221ae6d8a1e7ab974e288c19c3282d
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-tostring-returns-object-err.js
@@ -0,0 +1,56 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Abrupt completion when toString called and returns an object
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+      b. If IsCallable(method) is true, then
+        i. Let result be ? Call(method, O).
+        ii. If Type(result) is not Object, return result.
+    6. Throw a TypeError exception.
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+
+var thisVal = {
+  [Symbol.toPrimitive]: undefined,
+  toString: function() {
+    return {};
+  },
+};
+
+assert.throws(TypeError, function() {
+  String.prototype.trimEnd.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-call-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-call-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..ccd4516745256872ea95c027dce375da88174a69
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-call-err.js
@@ -0,0 +1,52 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Abrupt completion when getting valueOf method
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var thisVal = {
+  [Symbol.toPrimitive]: undefined,
+  toString: undefined,
+  get valueOf() {
+    throw new Test262Error();
+  },
+};
+
+assert.throws(Test262Error, function() {
+  String.prototype.trimEnd.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-meth-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-meth-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..386398aebbd14c31f2e3147b1ac7f34feb761322
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-meth-err.js
@@ -0,0 +1,54 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Abrupt completion when valueOf called and abrupt completes.
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+      b. If IsCallable(method) is true, then
+        i. Let result be ? Call(method, O).
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var thisVal = {
+  [Symbol.toPrimitive]: undefined,
+  toString: undefined,
+  valueOf: function() {
+    throw new Test262Error();
+  },
+};
+
+assert.throws(Test262Error, function() {
+  String.prototype.trimEnd.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-meth-priority.js b/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-meth-priority.js
new file mode 100644
index 0000000000000000000000000000000000000000..778846c07918816fbee2f22204d18275453ee16d
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-meth-priority.js
@@ -0,0 +1,91 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Priority of valueOf when converting object to string for trimming
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+      b. If IsCallable(method) is true, then
+        i. Let result be ? Call(method, O).
+        ii. If Type(result) is not Object, return result.
+   ...
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var toPrimitiveAccessed = 0;
+var toStringAccessed = 0;
+var valueOfAccessed = 0;
+var thisVal = {
+  get [Symbol.toPrimitive]() {
+    toPrimitiveAccessed += 1;
+    return undefined;
+  },
+  get toString() {
+    toStringAccessed += 1;
+    return undefined;
+  },
+  get valueOf() {
+    valueOfAccessed += 1;
+    return function() { return '42 '; };
+  },
+};
+
+// Test that valueOf is called when Symbol.toPrimitive and toString are both
+// undefined.
+
+var result = String.prototype.trimEnd.call(thisVal);
+
+assert.sameValue(
+  valueOfAccessed,
+  1,
+  'thisVal.toString expected to have been accessed.'
+);
+assert.sameValue(
+  result,
+  '42',
+  'thisVal.valueOf expected to have been called.',
+);
+
+// Test that thisVal[toPrimitive] and thisVal.toString has been accessed.
+
+assert.sameValue(
+  toPrimitiveAccessed,
+  1,
+  'thisVal[Symbol.toPrimitive should have been accessed.'
+);
+assert.sameValue(
+  toStringAccessed,
+  1,
+  'thisVal[Symbol.toString should have been accessed.'
+);
diff --git a/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-returns-object-err.js b/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-returns-object-err.js
new file mode 100644
index 0000000000000000000000000000000000000000..c1666660749b3af4c27dab28cde90bda0d4c2d6f
--- /dev/null
+++ b/test/built-ins/String/prototype/trimEnd/this-value-object-valueof-returns-object-err.js
@@ -0,0 +1,57 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimEnd
+description: >
+  Abrupt completion when valueOf called and returns an object
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+      b. If IsCallable(method) is true, then
+        i. Let result be ? Call(method, O).
+        ii. If Type(result) is not Object, return result.
+    6. Throw a TypeError exception.
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+
+var thisVal = {
+  [Symbol.toPrimitive]: undefined,
+  toString: undefined,
+  valueOf: function() {
+    return {};
+  },
+};
+
+assert.throws(TypeError, function() {
+  String.prototype.trimEnd.call(thisVal);
+});