[generators] Improve a test.

test/mjsunit/regress/regress-618657.js

Index: test/mjsunit/regress/regress-618657.js
diff --git a/test/mjsunit/regress/regress-618657.js b/test/mjsunit/regress/regress-618657.js
index 7bf84694301648bb492a499a3a11fa854b9c22b5..2882cff808ccae177c892572fdb8c67ca525c364 100644
--- a/test/mjsunit/regress/regress-618657.js
+++ b/test/mjsunit/regress/regress-618657.js
@@ -5,6 +5,10 @@
 // Flags: --ignition --ignition-generators --ignition-filter=-foo
 
 function* foo() { yield 42 }
-var g = foo();
+function* goo() { yield 42 }
+var f = foo();
+var g = goo();
+assertEquals(42, f.next().value);
 assertEquals(42, g.next().value);
+assertEquals(true, f.next().done);
 assertEquals(true, g.next().done);