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

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

@@ -24,6 +24,7 @@ package main
 
 import lib.A
 import lib.check
+import helpers.checkJsNames
 
 class B : A() {
     private var x = 42
@@ -31,13 +32,6 @@ class B : A() {
     fun bar() = x
 }
 
-// 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.x and B.x have different JS names.
-private fun checkJsNames(o: dynamic): Boolean = "x_i8qwny\$_0" in o && "x_0" in o
-
 fun box(): String {
     if (!check()) return "check failed: did not compile against old library"
 
@@ -47,7 +41,7 @@ fun box(): String {
     val b = B()
     if (b.foo() != 23) return "fail2: ${b.foo()}"
     if (b.bar() != 42) return "fail3: ${b.bar()}"
-    if (!checkJsNames(b)) return "fail4"
+    checkJsNames("x", b)
 
     return "OK"
 }