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Published: Nov 11, 2018 License: Apache-2.0 Imports: 2 Imported by: 5



Package poll provides tools for testing asynchronous code.




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func WaitOn

func WaitOn(t TestingT, check func(t LogT) Result, pollOps ...SettingOp)

WaitOn a condition or until a timeout. Poll by calling check and exit when check returns a done Result. To fail a test and exit polling with an error return a error result.

package main

import (

var t poll.TestingT

func numOfProcesses() (int, error) {
	return 0, nil

func main() {
	desired := 10

	check := func(t poll.LogT) poll.Result {
		actual, err := numOfProcesses()
		if err != nil {
			return poll.Error(errors.Wrap(err, "failed to get number of processes"))
		if actual == desired {
			return poll.Success()
		t.Logf("waiting on process count to be %d...", desired)
		return poll.Continue("number of processes is %d, not %d", actual, desired)

	poll.WaitOn(t, check)


type LogT

type LogT interface {
	Log(args ...interface{})
	Logf(format string, args ...interface{})

LogT is a logging interface that is passed to the WaitOn check function

type Result

type Result interface {
	// Error indicates that the check failed and polling should stop, and the
	// the has failed
	Error() error
	// Done indicates that polling should stop, and the test should proceed
	Done() bool
	// Message provides the most recent state when polling has not completed
	Message() string

Result of a check performed by WaitOn

func Continue

func Continue(message string, args ...interface{}) Result

Continue returns a Result that indicates to WaitOn that it should continue polling. The message text will be used as the failure message if the timeout is reached.

func Error

func Error(err error) Result

Error returns a Result that indicates to WaitOn that it should fail the test and stop polling.

func Success

func Success() Result

Success returns a Result where Done() returns true, which indicates to WaitOn that it should stop polling and exit without an error.

type SettingOp

type SettingOp func(config *Settings)

SettingOp is a function which accepts and modifies Settings

package main

import (


var t poll.TestingT

func isDesiredState() bool { return false }
func getState() string     { return "" }

func main() {
	check := func(t poll.LogT) poll.Result {
		if isDesiredState() {
			return poll.Success()
		return poll.Continue("state is: %s", getState())
	poll.WaitOn(t, check, poll.WithTimeout(30*time.Second), poll.WithDelay(15*time.Millisecond))

func WithDelay

func WithDelay(delay time.Duration) SettingOp

WithDelay sets the delay to wait between polls

func WithTimeout

func WithTimeout(timeout time.Duration) SettingOp

WithTimeout sets the timeout

type Settings

type Settings struct {
	// Timeout is the maximum time to wait for the condition. Defaults to 10s.
	Timeout time.Duration
	// Delay is the time to sleep between checking the condition. Defaults to
	// 100ms.
	Delay time.Duration

Settings are used to configure the behaviour of WaitOn

type TestingT

type TestingT interface {
	Fatalf(format string, args ...interface{})

TestingT is the subset of testing.T used by WaitOn

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