diff --git a/src/browser/tests/document/query_selector.html b/src/browser/tests/document/query_selector.html
index b333069e..0837999e 100644
--- a/src/browser/tests/document/query_selector.html
+++ b/src/browser/tests/document/query_selector.html
@@ -24,11 +24,10 @@
 
 <script id=byId name="test1">
   testing.expectEqual(1, document.querySelector.length);
-  testing.expectError("SyntaxError: Syntax Error", () => document.querySelector(''));
+  testing.expectError("SyntaxError", () => document.querySelector(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
-    testing.expectEqual("Syntax Error", err.message);
   }, () => document.querySelector(''));
 
   testing.expectEqual('test1', document.querySelector('#byId').getAttribute('name'));
diff --git a/src/browser/tests/document/query_selector_all.html b/src/browser/tests/document/query_selector_all.html
index ae95ed9e..46007740 100644
--- a/src/browser/tests/document/query_selector_all.html
+++ b/src/browser/tests/document/query_selector_all.html
@@ -34,11 +34,10 @@
 </script>
 
 <script id=script1 name="test1">
-  testing.expectError("SyntaxError: Syntax Error", () => document.querySelectorAll(''));
+  testing.expectError("SyntaxError", () => document.querySelectorAll(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
-    testing.expectEqual("Syntax Error", err.message);
   }, () => document.querySelectorAll(''));
 </script>
 
diff --git a/src/browser/tests/domexception.html b/src/browser/tests/domexception.html
index 1ed43e8d..05bdc837 100644
--- a/src/browser/tests/domexception.html
+++ b/src/browser/tests/domexception.html
@@ -127,7 +127,7 @@
 
   testing.withError((err) => {
     testing.expectEqual(3, err.code);
-    testing.expectEqual('Hierarchy Error', err.message);
+    testing.expectEqual('HierarchyRequestError', err.name);
     testing.expectEqual(true, err instanceof DOMException);
     testing.expectEqual(true, err instanceof Error);
   }, () => link.appendChild(content));
diff --git a/src/browser/tests/element/attributes.html b/src/browser/tests/element/attributes.html
index 9b8c29d3..0929a3d9 100644
--- a/src/browser/tests/element/attributes.html
+++ b/src/browser/tests/element/attributes.html
@@ -36,7 +36,6 @@
   testing.withError((err) => {
     testing.expectEqual(8, err.code);
     testing.expectEqual("NotFoundError", err.name);
-    testing.expectEqual("Not Found", err.message);
   }, () => el1.removeAttributeNode(script_id_node));
 
   testing.expectEqual(an1, el1.removeAttributeNode(an1));
diff --git a/src/browser/tests/element/matches.html b/src/browser/tests/element/matches.html
index 5e1721b5..f28d7a71 100644
--- a/src/browser/tests/element/matches.html
+++ b/src/browser/tests/element/matches.html
@@ -66,11 +66,10 @@
 {
   const container = $('#test-container');
 
-  testing.expectError("SyntaxError: Syntax Error", () => container.matches(''));
+  testing.expectError("SyntaxError", () => container.matches(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
-    testing.expectEqual("Syntax Error", err.message);
   }, () => container.matches(''));
 }
 </script>
diff --git a/src/browser/tests/element/query_selector.html b/src/browser/tests/element/query_selector.html
index 9564ca6d..203524b6 100644
--- a/src/browser/tests/element/query_selector.html
+++ b/src/browser/tests/element/query_selector.html
@@ -12,11 +12,10 @@
   const p1 = $('#p1');
   testing.expectEqual(null, p1.querySelector('#p1'));
 
-  testing.expectError("SyntaxError: Syntax Error", () => p1.querySelector(''));
+  testing.expectError("SyntaxError", () => p1.querySelector(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
-    testing.expectEqual("Syntax Error", err.message);
   }, () => p1.querySelector(''));
 
   testing.expectEqual($('#c2'), p1.querySelector('#c2'));
diff --git a/src/browser/tests/element/query_selector_all.html b/src/browser/tests/element/query_selector_all.html
index eeedc876..3b4013c2 100644
--- a/src/browser/tests/element/query_selector_all.html
+++ b/src/browser/tests/element/query_selector_all.html
@@ -24,11 +24,10 @@
 <script id=errors>
 {
   const root = $('#root');
-  testing.expectError("SyntaxError: Syntax Error", () => root.querySelectorAll(''));
+  testing.expectError("SyntaxError", () => root.querySelectorAll(''));
   testing.withError((err) => {
     testing.expectEqual(12, err.code);
     testing.expectEqual("SyntaxError", err.name);
-    testing.expectEqual("Syntax Error", err.message);
   }, () => root.querySelectorAll(''));
 }
 </script>
diff --git a/src/browser/tests/element/selector_invalid.html b/src/browser/tests/element/selector_invalid.html
index 35409c19..c0d16d59 100644
--- a/src/browser/tests/element/selector_invalid.html
+++ b/src/browser/tests/element/selector_invalid.html
@@ -43,8 +43,8 @@
     const container = $('#container');
 
     // Empty selectors
-    testing.expectError("SyntaxError: Syntax Error", () => container.querySelector(''));
-    testing.expectError("SyntaxError: Syntax Error", () => document.querySelectorAll(''));
+    testing.expectError("SyntaxError", () => container.querySelector(''));
+    testing.expectError("SyntaxError", () => document.querySelectorAll(''));
 }
 </script>
 
diff --git a/src/browser/tests/node/insert_before.html b/src/browser/tests/node/insert_before.html
index 8be48e56..50dff07c 100644
--- a/src/browser/tests/node/insert_before.html
+++ b/src/browser/tests/node/insert_before.html
@@ -19,7 +19,6 @@
   testing.withError((err) => {
     testing.expectEqual(8, err.code);
     testing.expectEqual("NotFoundError", err.name);
-    testing.expectEqual("Not Found", err.message);
   }, () => d1.insertBefore(document.createElement('div'), d2));
 
   let c1 = document.createElement('div');
diff --git a/src/browser/tests/node/remove_child.html b/src/browser/tests/node/remove_child.html
index fdf0b813..1118e4cf 100644
--- a/src/browser/tests/node/remove_child.html
+++ b/src/browser/tests/node/remove_child.html
@@ -7,7 +7,6 @@
   testing.withError((err) => {
     testing.expectEqual(8, err.code);
     testing.expectEqual("NotFoundError", err.name);
-    testing.expectEqual("Not Found", err.message);
   }, () => $('#d1').removeChild($('#p1')));
 
   const p1 = $('#p1');
diff --git a/src/browser/tests/node/replace_child.html b/src/browser/tests/node/replace_child.html
index 45ed1bc5..51b0a173 100644
--- a/src/browser/tests/node/replace_child.html
+++ b/src/browser/tests/node/replace_child.html
@@ -25,7 +25,6 @@
   testing.withError((err) => {
     testing.expectEqual(3, err.code);
     testing.expectEqual("HierarchyRequestError", err.name);
-    testing.expectEqual("Hierarchy Error", err.message);
   }, () => d1.replaceChild(c4, c3));
 
   testing.expectEqual(c2, d1.replaceChild(c4, c2));
diff --git a/src/browser/tests/range.html b/src/browser/tests/range.html
index d9a8637b..8440c187 100644
--- a/src/browser/tests/range.html
+++ b/src/browser/tests/range.html
@@ -451,12 +451,12 @@
   const p1 = $('#p1');
 
   // Test setStart with offset beyond node length
-  testing.expectError('IndexSizeError: Index or size is negative or greater than the allowed amount', () => {
+  testing.expectError('IndexSizeError:', () => {
     range.setStart(p1, 999);
   });
 
   // Test with negative offset (wraps to large u32)
-  testing.expectError('IndexSizeError: Index or size is negative or greater than the allowed amount', () => {
+  testing.expectError('IndexSizeError:', () => {
     range.setStart(p1.firstChild, -1);
   });
 }
@@ -468,12 +468,12 @@
   const p1 = $('#p1');
 
   // Test setEnd with offset beyond node length
-  testing.expectError('IndexSizeError: Index or size is negative or greater than the allowed amount', () => {
+  testing.expectError('IndexSizeError:', () => {
     range.setEnd(p1, 999);
   });
 
   // Test with text node
-  testing.expectError('IndexSizeError: Index or size is negative or greater than the allowed amount', () => {
+  testing.expectError('IndexSizeError:', () => {
     range.setEnd(p1.firstChild, 9999);
   });
 }
@@ -525,11 +525,11 @@
   range.setEnd(p1, 1);
 
   // Test comparePoint with invalid offset
-  testing.expectError('IndexSizeError: Index or size is negative or greater than the allowed amount', () => {
+  testing.expectError('IndexSizeError:', () => {
     range.comparePoint(p1, 20);
   });
 
-  testing.expectError('IndexSizeError: Index or size is negative or greater than the allowed amount', () => {
+  testing.expectError('IndexSizeError:', () => {
     range.comparePoint(p1.firstChild, -1);
   });
 }
@@ -650,11 +650,11 @@
   range.setEnd(p1, 1);
 
   // Invalid offset should throw IndexSizeError
-  testing.expectError('IndexSizeError: Index or size is negative or greater than the allowed amount', () => {
+  testing.expectError('IndexSizeError:', () => {
     range.isPointInRange(p1, 999);
   });
 
-  testing.expectError('IndexSizeError: Index or size is negative or greater than the allowed amount', () => {
+  testing.expectError('IndexSizeError:', () => {
     range.isPointInRange(p1.firstChild, 9999);
   });
 }
@@ -854,11 +854,11 @@
   range2.setStart(p, 0);
 
   // Invalid how parameter should throw NotSupportedError
-  testing.expectError('NotSupportedError: Not Supported', () => {
+  testing.expectError('NotSupportedError:', () => {
     range1.compareBoundaryPoints(4, range2);
   });
 
-  testing.expectError('NotSupportedError: Not Supported', () => {
+  testing.expectError('NotSupportedError:', () => {
     range1.compareBoundaryPoints(99, range2);
   });
 }
@@ -883,7 +883,7 @@
   range2.setEnd(foreignP, 1);
 
   // Comparing ranges in different documents should throw WrongDocumentError
-  testing.expectError('WrongDocumentError: wrong_document_error', () => {
+  testing.expectError('WrongDocumentError:', () => {
     range1.compareBoundaryPoints(Range.START_TO_START, range2);
   });
 }
diff --git a/src/browser/tests/window/window.html b/src/browser/tests/window/window.html
index 01025b86..e4094f9b 100644
--- a/src/browser/tests/window/window.html
+++ b/src/browser/tests/window/window.html
@@ -82,7 +82,7 @@
   testing.expectEqual('ceil', atob('Y2VpbA'));  // 6 chars, len%4==2, needs '=='
 
   // length % 4 == 1 must still throw
-  testing.expectError('InvalidCharacterError: Invalid Character', () => {
+  testing.expectError('InvalidCharacterError', () => {
     atob('Y');
   });
 </script>