metropolis/test/util/runners.go

// This file implements test helper functions that augment the way any given
// test is run.
package util

import (
	"context"
	"errors"
	"testing"
	"time"
)

// TestEventual creates a new subtest looping the given function until it
// either doesn't return an error anymore or the timeout is exceeded. The last
// returned non-context-related error is being used as the test error.
func TestEventual(t *testing.T, name string, ctx context.Context, timeout time.Duration, f func(context.Context) error) {
	ctx, cancel := context.WithTimeout(ctx, timeout)
	t.Helper()
	t.Run(name, func(t *testing.T) {
		defer cancel()
		var lastErr = errors.New("test didn't run to completion at least once")
		t.Parallel()
		for {
			err := f(ctx)
			if err == nil {
				return
			}
			if err == ctx.Err() {
				t.Fatal(lastErr)
			}
			lastErr = err
			select {
			case <-ctx.Done():
				t.Fatal(lastErr)
			case <-time.After(1 * time.Second):
			}
		}
	})
}