   _ = bytes[1]
 }
 
-UnsafeRawBufferPointerTestSuite.test("subscript.set.underflow") {
+// FIXME: rdar:31495442. Enable this in release builds too.
+UnsafeRawBufferPointerTestSuite.test("subscript.set.underflow")
+.skip(.custom(
+    { !_isDebugAssertConfiguration() },
+    reason: "This tests a debug precondition."))
+.code {
   let buffer = UnsafeMutableRawBufferPointer.allocate(count: 2)
   defer { buffer.deallocate() }
 

  expectEqualSequence(firstHalf, secondHalf)
}

UnsafeRawBufferPointerTestSuite.test("subscript.get.underflow") {
  let buffer = UnsafeMutableRawBufferPointer.allocate(count: 2)
  defer { buffer.deallocate() }


  bytes[1] = 0
}

// FIXME: rdar:31495442. Enable this in release builds too.
UnsafeRawBufferPointerTestSuite.test("subscript.range.get.underflow")
.skip(.custom(
    { !_isDebugAssertConfiguration() },
    reason: "This tests a debug precondition."))
.code {
  let buffer = UnsafeMutableRawBufferPointer.allocate(count: 3)
  defer { buffer.deallocate() }

