Check in codegen test expectations.

test/codegen/expect/corelib/exception_implementation_test.js

Index: test/codegen/expect/corelib/exception_implementation_test.js
diff --git a/test/codegen/expect/corelib/exception_implementation_test.js b/test/codegen/expect/corelib/exception_implementation_test.js
new file mode 100644
index 0000000000000000000000000000000000000000..71d388501178a71d6ef76db1be8a9145b920fe80
--- /dev/null
+++ b/test/codegen/expect/corelib/exception_implementation_test.js
@@ -0,0 +1,29 @@
+dart_library.library('corelib/exception_implementation_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__exception_implementation_test(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const exception_implementation_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  exception_implementation_test.main = function() {
+    let msg = 1;
+    try {
+      dart.throw(core.Exception.new(msg));
+      expect$.Expect.fail("Unreachable");
+    } catch (e) {
+      if (core.Exception.is(e)) {
+        expect$.Expect.isTrue(core.Exception.is(e));
+        expect$.Expect.equals(dart.str`Exception: ${msg}`, dart.toString(e));
+      } else
+        throw e;
+    }
+
+  };
+  dart.fn(exception_implementation_test.main, VoidTodynamic());
+  // Exports:
+  exports.exception_implementation_test = exception_implementation_test;
+});