   return s
 }
 
-StringTests.test("stringCoreExtensibility") {
+StringTests.test("stringCoreExtensibility")
+  .skip(.LinuxAny(reason: "Foundation dependency"))
+  .code {
+#if _runtime(_ObjC)
   let ascii = UTF16.CodeUnit(UnicodeScalar("X").value)
   let nonAscii = UTF16.CodeUnit(UnicodeScalar("é").value)
 

import SwiftPrivate
#if _runtime(_ObjC)
import ObjectiveC
#endif

import Foundation

extension String {
  var bufferID: UInt {

  }

  expectEqual(["furth", "lard", "bart"], matches)
#else
  expectUnreachable()
#endif
}

StringTests.test("String.append(_: UnicodeScalar)") {
