From a1e7fb4eed7fbb002d2fabbd6a809a1a49dca711 Mon Sep 17 00:00:00 2001 From: Josh Bleecher Snyder Date: Fri, 7 Jul 2017 13:09:20 -1000 Subject: [PATCH] test: deflake chan/select3.go On a slow or distracted machine, 0.1s is sometimes not long enough for a non-blocking function call to complete. This causes rare test flakes. They can be easily reproduced by reducing the wait time to (say) 100ns. For non-blocking functions, increase the window from 100ms to 10s. Using different windows for block and non-blocking functions, allows us to reduce the time for blocking functions. The risk here is false negatives, but that risk is low; this test is run repeatedly on many fast machines, for which 10ms is ample time. This reduces the time required to run the test by a factor of 10, from ~1s to ~100ms. Fixes #20299 Change-Id: Ice9a641a66c6c101d738a2ebe1bcb144ae3c9916 Reviewed-on: https://go-review.googlesource.com/47812 Run-TryBot: Josh Bleecher Snyder Reviewed-by: Brad Fitzpatrick TryBot-Result: Gobot Gobot --- test/chan/select3.go | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/test/chan/select3.go b/test/chan/select3.go index e9391f55c7..dd14c7381e 100644 --- a/test/chan/select3.go +++ b/test/chan/select3.go @@ -40,8 +40,15 @@ func testBlock(signal string, f func()) { c <- never // f didn't block }() go func() { - time.Sleep(1e8) // 0.1s seems plenty long - c <- always // f blocked always + if signal == never { + // Wait a long time to make sure that we don't miss our window by accident on a slow machine. + time.Sleep(10 * time.Second) + } else { + // Wait as short a time as we can without false negatives. + // 10ms should be long enough to catch most failures. + time.Sleep(10 * time.Millisecond) + } + c <- always // f blocked always }() if <-c != signal { panic(signal + " block")