diff --git a/test/suite/es6/Number.isNaN/Number.isNaN_Boolean.js b/test/suite/es6/Number.isNaN/Number.isNaN_Boolean.js
index bc984f4d1a608fe6fd5e3c3acb5bdadce0d0a1bb..e18c57f9bbfadb425677cb4b05b38417a18b2c93 100644
--- a/test/suite/es6/Number.isNaN/Number.isNaN_Boolean.js
+++ b/test/suite/es6/Number.isNaN/Number.isNaN_Boolean.js
@@ -13,6 +13,6 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  return Number.isNaN(true);
+  return Number.isNaN(true) === false;
  }
 runTestCase(testcase);
diff --git a/test/suite/es6/Number.isNaN/Number.isNaN_NaN.js b/test/suite/es6/Number.isNaN/Number.isNaN_NaN.js
index 79ddbfa9ba31d161fc74c01bcd63b0dd1c9c5617..6a96ccc27cf7b2a33480cd1a5e6fbf5a875f2468 100644
--- a/test/suite/es6/Number.isNaN/Number.isNaN_NaN.js
+++ b/test/suite/es6/Number.isNaN/Number.isNaN_NaN.js
@@ -13,6 +13,6 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  return Number.isNaN(NaN);
+  return Number.isNaN(NaN) === true;
  }
 runTestCase(testcase);
diff --git a/test/suite/es6/Number.isNaN/Number.isNaN_Object.js b/test/suite/es6/Number.isNaN/Number.isNaN_Object.js
index b088e4323deeec7d35fbe72016d3482fddf6cada..2aff516b5cd639b6bddbea8e1ea637b3bbc541c1 100644
--- a/test/suite/es6/Number.isNaN/Number.isNaN_Object.js
+++ b/test/suite/es6/Number.isNaN/Number.isNaN_Object.js
@@ -15,6 +15,6 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  return !Number.isNaN(new Object());
+  return Number.isNaN(new Object()) === false;
  }
 runTestCase(testcase);
diff --git a/test/suite/es6/Number.isNaN/Number.isNaN_String.js b/test/suite/es6/Number.isNaN/Number.isNaN_String.js
index b50ee38db351f5f1cad62c211cdf40443d16c24d..f5f8ef5040b463b7786f5f43094b7dfd15b9f7ed 100644
--- a/test/suite/es6/Number.isNaN/Number.isNaN_String.js
+++ b/test/suite/es6/Number.isNaN/Number.isNaN_String.js
@@ -13,6 +13,6 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  return !Number.isNaN('string');
+  return Number.isNaN('string') === false;
  }
 runTestCase(testcase);
diff --git a/test/suite/es6/String.prototype.contains/String.prototype.contains_Success.js b/test/suite/es6/String.prototype.contains/String.prototype.contains_Success.js
index c653e6957a708d9f6285bdf9af1656d82bdff8aa..a7d99ad9adac1f6d47afcd32f26da242ba501115 100644
--- a/test/suite/es6/String.prototype.contains/String.prototype.contains_Success.js
+++ b/test/suite/es6/String.prototype.contains/String.prototype.contains_Success.js
@@ -15,7 +15,7 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  if('word'.contains('w', 0)) {
+  if('word'.contains('w', 0) === true) {
   	return true;
   }
  }
diff --git a/test/suite/es6/String.prototype.contains/String.prototype.contains_SuccessNoLocation.js b/test/suite/es6/String.prototype.contains/String.prototype.contains_SuccessNoLocation.js
index dc98cd2582c0c2beaffb73db9450ea95e5ab24d8..cd1c00cae822dcf35849333f19da3647b6a51e37 100644
--- a/test/suite/es6/String.prototype.contains/String.prototype.contains_SuccessNoLocation.js
+++ b/test/suite/es6/String.prototype.contains/String.prototype.contains_SuccessNoLocation.js
@@ -15,7 +15,7 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  if('word'.contains('w')) {
+  if('word'.contains('w') === true) {
   	return true;
   }
  }
diff --git a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Fail.js b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Fail.js
index 8e34faaa7c62145a915b8e283476f739de5223bf..cab5e1c5430f7c76a5fd2d988cd9233242ef3224 100644
--- a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Fail.js
+++ b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Fail.js
@@ -13,7 +13,7 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  if('word'.endsWith('r')) {
+  if('word'.endsWith('r') === false) {
   	return true;
   }
  }
diff --git a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Fail_2.js b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Fail_2.js
index df4a5c5724ba2e52b64c88528345575383cdbe40..00c9854ce94ab81db0d7c415eb3291c573598320 100644
--- a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Fail_2.js
+++ b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Fail_2.js
@@ -15,7 +15,7 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  if('word'.endsWith('d',3)) {
+  if('word'.endsWith('d', 3) === false) {
   	return true;
   }
  }
diff --git a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success.js b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success.js
index 4128c4d3357f38ed6d429fcc37aa9f09d3aaf07d..ae115452e175c84147298e8149fb190c6b50e3f6 100644
--- a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success.js
+++ b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success.js
@@ -15,7 +15,7 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  if('word'.endsWith('d')) {
+  if('word'.endsWith('d') === true) {
   	return true;
   }
  }
diff --git a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_2.js b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_2.js
index 4314942775f21a9d72f4c74149658582f2b565a0..b9b1d98c8cc70d9094622b389ed3f30aba1f94f3 100644
--- a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_2.js
+++ b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_2.js
@@ -15,7 +15,7 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  if('word'.endsWith('d', 4)) {
+  if('word'.endsWith('d', 4) === true) {
   	return true;
   }
  }
diff --git a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_3.js b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_3.js
index 369b76c15497aeef060d4cb98d8abc88e2f56666..7e7352d4ab9a60c942e68c5cd728b945bcb02038 100644
--- a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_3.js
+++ b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_3.js
@@ -15,7 +15,7 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  if('word'.endsWith('d', 25)) {
+  if('word'.endsWith('d', 25) === true) {
   	return true;
   }
  }
diff --git a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_4.js b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_4.js
index 1954027b9a1d0c60c5a3672996a1cbd8ad66da22..0da8b5edb6af85732d173aff96e1c6c07021155a 100644
--- a/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_4.js
+++ b/test/suite/es6/String.prototype.endsWith/String.prototype.endsWith_Success_4.js
@@ -15,7 +15,7 @@ includes: [runTestCase.js]
 ---*/
 
 function testcase() {
-  if('word'.endsWith('r',3)) {
+  if('word'.endsWith('r', 3) === true) {
   	return true;
   }
  }