[tests] Fix bogus uses of assertThrows.

test/mjsunit/mjsunit.js

Index: test/mjsunit/mjsunit.js
diff --git a/test/mjsunit/mjsunit.js b/test/mjsunit/mjsunit.js
index 27f4d3942ad035fe9f743702381c7e6cff783737..9b07953c8aa22a24cd1386e1f212027dab0c7e2f 100644
--- a/test/mjsunit/mjsunit.js
+++ b/test/mjsunit/mjsunit.js
@@ -93,6 +93,10 @@ var assertNotNull;
 // to the type property on the thrown exception.
 var assertThrows;
 
+// Assert that the passed function throws an exception.
+// The exception is checked against the second argument using assertEquals.
+var assertThrowsEquals;
+
 // Assert that the passed function or eval code does not throw an exception.
 var assertDoesNotThrow;
 
@@ -353,6 +357,8 @@ var assertUnoptimized;
     } catch (e) {
       if (typeof type_opt === 'function') {
         assertInstanceof(e, type_opt);
+      } else if (type_opt !== void 0) {
+        fail("invalid use of assertThrows, maybe you want assertThrowsEquals");
       }
       if (arguments.length >= 3) {
         assertEquals(e.type, cause_opt);
@@ -364,6 +370,17 @@ var assertUnoptimized;
   };
 
 
+  assertThrowsEquals = function assertThrowsEquals(fun, val) {
+    try {
+      fun();
+    } catch(e) {
+      assertEquals(val, e);
+      return;
+    }
+    throw new MjsUnitAssertionError("Did not throw exception");
+  };
+
+
   assertInstanceof = function assertInstanceof(obj, type) {
     if (!(obj instanceof type)) {
       var actualTypeName = null;