diff --git a/packages/core/src/util/assert.ts b/packages/core/src/util/assert.ts
index 165241ab1d..fc9ddc8412 100644
--- a/packages/core/src/util/assert.ts
+++ b/packages/core/src/util/assert.ts
@@ -14,68 +14,78 @@ import {stringify} from './stringify';
 
 export function assertNumber(actual: any, msg: string) {
   if (typeof actual != 'number') {
-    throwError(msg);
+    throwError(msg, typeof actual, 'number', '===');
+  }
+}
+
+export function assertString(actual: any, msg: string) {
+  if (typeof actual != 'string') {
+    throwError(msg, actual === null ? 'null' : typeof actual, 'string', '===');
   }
 }
 
 export function assertEqual<T>(actual: T, expected: T, msg: string) {
   if (actual != expected) {
-    throwError(msg);
+    throwError(msg, actual, expected, '==');
   }
 }
 
 export function assertNotEqual<T>(actual: T, expected: T, msg: string) {
   if (actual == expected) {
-    throwError(msg);
+    throwError(msg, actual, expected, '!=');
   }
 }
 
 export function assertSame<T>(actual: T, expected: T, msg: string) {
   if (actual !== expected) {
-    throwError(msg);
+    throwError(msg, actual, expected, '===');
   }
 }
 
 export function assertNotSame<T>(actual: T, expected: T, msg: string) {
   if (actual === expected) {
-    throwError(msg);
+    throwError(msg, actual, expected, '!==');
   }
 }
 
 export function assertLessThan<T>(actual: T, expected: T, msg: string) {
   if (actual >= expected) {
-    throwError(msg);
+    throwError(msg, actual, expected, '<');
   }
 }
 
 export function assertLessThanOrEqual<T>(actual: T, expected: T, msg: string) {
   if (actual > expected) {
-    throwError(msg);
+    throwError(msg, actual, expected, '<=');
   }
 }
 
 export function assertGreaterThan<T>(actual: T, expected: T, msg: string) {
   if (actual <= expected) {
-    throwError(msg);
+    throwError(msg, actual, expected, '>');
   }
 }
 
 export function assertNotDefined<T>(actual: T, msg: string) {
   if (actual != null) {
-    throwError(msg);
+    throwError(msg, actual, null, '==');
   }
 }
 
 export function assertDefined<T>(actual: T, msg: string) {
   if (actual == null) {
-    throwError(msg);
+    throwError(msg, actual, null, '!=');
   }
 }
 
-export function throwError(msg: string): never {
+export function throwError(msg: string): never;
+export function throwError(msg: string, actual: any, expected: any, comparison: string): never;
+export function throwError(msg: string, actual?: any, expected?: any, comparison?: string): never {
   // tslint:disable-next-line
   debugger;  // Left intentionally for better debugger experience.
-  throw new Error(`ASSERTION ERROR: ${msg}`);
+  throw new Error(
+      `ASSERTION ERROR: ${msg}` +
+      (comparison == null ? '' : ` [Expected=> ${expected} ${comparison} ${actual} <=Actual]`));
 }
 
 export function assertDomNode(node: any) {