KT-2752: fix some tests and make them slightly less fragile

js/js.translator/testData/box/multiModule/privateInterfaceNameClash.kt

@@ -24,6 +24,7 @@ package main
 
 import lib1.A
 import lib2.B
+import helpers.checkJsNames
 
 class Derived1 : A, B {
     override fun bar() = super<A>.bar()
@@ -33,13 +34,6 @@ class Derived2 : A, B {
     override fun bar() = super<B>.bar()
 }
 
-// NOTE. This test is fragile, it may fail due to unexpected (and correct) changes in algorithm that assigns
-// unique identifiers to non-public declarations. However, we don't see any way of doing such test so that
-// it won't report false positives eventually. So be patient and just update this test whenever you changed
-// algorithm of assigning unique identifiers.
-// Please, check that A.foo and B.foo have different JS names.
-private fun checkJsNames(o: dynamic): Boolean = "foo_2pru9n\$_0" in o && "foo_2psha1\$_0" in o
-
 fun box(): String {
     val a = Derived1()
     if (a.bar() != "A.foo") return "fail1: ${a.bar()}"
@@ -47,8 +41,8 @@ fun box(): String {
     val b = Derived2()
     if (b.bar() != "B.foo") return "fail2: ${b.bar()}"
 
-    if (!checkJsNames(a)) return "fail3"
-    if (!checkJsNames(b)) return "fail4"
+    checkJsNames("foo", a)
+    checkJsNames("foo", b)
 
     return "OK"
 }