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testing: add -shuffle=off|on|N to alter the execution order of tests and benchmarks

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This CL adds a new flag to the testing package and the go test command
which randomizes the execution order for tests and benchmarks.
This can be useful for identifying unwanted dependencies
between test or benchmark functions.
The flag is off by default. If `-shuffle` is set to `on` then the system
clock will be used as the seed value. If `-shuffle` is set to an integer
N, then N will be used as the seed value. In both cases, the seed will
be reported for failed runs so that they can reproduced later on.

Fixes #28592

Change-Id: I62e7dfae5f63f97a0cbd7830ea844d9f7beac335
Reviewed-on: https://go-review.googlesource.com/c/go/+/310033
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Trust: Bryan C. Mills <bcmills@google.com>
This commit is contained in:
Paschalis Tsilias 2021-04-14 23:55:38 +03:00 • committed by Ian Lance Taylor
parent e51246c881
commit cbb3f09047
10 changed files with 249 additions and 4 deletions
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22
src/testing/testing.go
View file

@ -242,6 +242,7 @@ import (
"fmt"
"internal/race"
"io"
"math/rand"
"os"
"runtime"
"runtime/debug"
@ -299,6 +300,7 @@ func Init() {
cpuListStr = flag.String("test.cpu", "", "comma-separated `list` of cpu counts to run each test with")
parallel = flag.Int("test.parallel", runtime.GOMAXPROCS(0), "run at most `n` tests in parallel")
testlog = flag.String("test.testlogfile", "", "write test action log to `file` (for use only by cmd/go)")
shuffle = flag.String("test.shuffle", "off", "randomize the execution order of tests and benchmarks")
initBenchmarkFlags()
}
@ -325,6 +327,7 @@ var (
timeout *time.Duration
cpuListStr *string
parallel *int
shuffle *string
testlog *string
haveExamples bool // are there examples?
@ -1456,6 +1459,25 @@ func (m *M) Run() (code int) {
return
}
if *shuffle != "off" {
var n int64
var err error
if *shuffle == "on" {
n = time.Now().UnixNano()
} else {
n, err = strconv.ParseInt(*shuffle, 10, 64)
if err != nil {
fmt.Fprintln(os.Stderr, `testing: -shuffle should be "off", "on", or a valid integer:`, err)
m.exitCode = 2
return
}
}
fmt.Println("-test.shuffle", n)
rng := rand.New(rand.NewSource(n))
rng.Shuffle(len(m.tests), func(i, j int) { m.tests[i], m.tests[j] = m.tests[j], m.tests[i] })
rng.Shuffle(len(m.benchmarks), func(i, j int) { m.benchmarks[i], m.benchmarks[j] = m.benchmarks[j], m.benchmarks[i] })
}
parseCpuList()
m.before()