events.go

/*
Copyright 2021 The Tekton Authors

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package k8sevent

import (
	"fmt"
	"regexp"
	"testing"
	"time"

	"k8s.io/apimachinery/pkg/util/wait"
)

// CheckEventsOrdered checks that the events received via the given chan are the same as wantEvents,
// in the same order.
func CheckEventsOrdered(t *testing.T, eventChan chan string, testName string, wantEvents []string) error {
	t.Helper()
	err := eventsFromChannel(eventChan, wantEvents)
	if err != nil {
		return fmt.Errorf("error in test %s: %w", testName, err)
	}
	return nil
}

// eventsFromChannel takes a chan of string, a test name, and a list of events that a test
// expects to receive. The events must be received in the same order they appear in the
// wantEvents list. Any extra or too few received events are considered errors.
func eventsFromChannel(c chan string, wantEvents []string) error {
	// We get events from a channel, so the timeout is here to avoid waiting
	// on the channel forever if fewer than expected events are received.
	// We only hit the timeout in case of failure of the test, so the actual value
	// of the timeout is not so relevant, it's only used when tests are going to fail.
	// on the channel forever if fewer than expected events are received
	timer := time.After(wait.ForeverTestTimeout)
	foundEvents := []string{}
	for ii := 0; ii < len(wantEvents); ii++ {
		// We loop over all the events that we expect. Once they are all received
		// we exit the loop. If we never receive enough events, the timeout takes us
		// out of the loop.
		select {
		case event := <-c:
			foundEvents = append(foundEvents, event)
			wantEvent := wantEvents[ii]
			// If the event is an exact match, there is no need to use regular expressions for matching.
			// This can avoid the need to escape special characters, such as *, in the event to match.
			if wantEvent == event {
				continue
			}
			matching, err := regexp.MatchString(wantEvent, event)
			if err == nil {
				if !matching {
					return fmt.Errorf("expected event \"%s\" but got \"%s\" instead", wantEvent, event)
				}
			} else {
				return fmt.Errorf("something went wrong matching the event: %w", err)
			}
		case <-timer:
			return fmt.Errorf("received %d events but %d expected. Found events: %#v", len(foundEvents), len(wantEvents), foundEvents)
		}
	}
	// Check if there are extra events in the channel, return error if found.
	for {
		select {
		case event := <-c:
			return fmt.Errorf("unexpected event: %q", event)
		default:
			return nil
		}
	}
}