allow randomizing scenario order

options.go

@@ -13,6 +13,13 @@ type Options struct {
 	// Print step definitions found and exit
 	ShowStepDefinitions bool
 
+	// Run scenarios in random order.
+	//
+	// This is especially helpful for detecting situations
+	// where you have state leaking between scenarios, which
+	// can cause flickering or fragile tests.
+	RandomOrder bool
+
 	// Stops on the first failure
 	StopOnFailure bool
 

run.go

@@ -3,7 +3,9 @@ package godog
 import (
 	"fmt"
 	"io"
+	"math/rand"
 	"os"
+	"time"
 
 	"github.com/DATA-DOG/godog/colors"
 )
@@ -11,6 +13,7 @@ import (
 type initializer func(*Suite)
 
 type runner struct {
+	randomOrder   bool
 	stopOnFailure bool
 	features      []*feature
 	fmt           Formatter
@@ -30,6 +33,7 @@ func (r *runner) concurrent(rate int) (failed bool) {
 			}
 			suite := &Suite{
 				fmt:           r.fmt,
+				randomOrder:   r.randomOrder,
 				stopOnFailure: r.stopOnFailure,
 				features:      []*feature{feat},
 			}
@@ -54,6 +58,7 @@ func (r *runner) concurrent(rate int) (failed bool) {
 func (r *runner) run() (failed bool) {
 	suite := &Suite{
 		fmt:           r.fmt,
+		randomOrder:   r.randomOrder,
 		stopOnFailure: r.stopOnFailure,
 		features:      r.features,
 	}
@@ -110,9 +115,16 @@ func RunWithOptions(suite string, contextInitializer func(suite *Suite), opt Opt
 		fmt:           formatter(suite, output),
 		initializer:   contextInitializer,
 		features:      features,
+		randomOrder:   opt.RandomOrder,
 		stopOnFailure: opt.StopOnFailure,
 	}
 
+	if opt.RandomOrder {
+		// TODO(mroth): allow for seed to be specified in options,
+		// and print it at the end of a run for replication purposes
+		rand.Seed(time.Now().UTC().UnixNano())
+	}
+
 	var failed bool
 	if opt.Concurrency > 1 {
 		failed = r.concurrent(opt.Concurrency)

suite.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"math/rand"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -49,6 +50,7 @@ type Suite struct {
 	fmt      Formatter
 
 	failed        bool
+	randomOrder   bool
 	stopOnFailure bool
 
 	// suite event handlers
@@ -330,7 +332,20 @@ func (s *Suite) runOutline(outline *gherkin.ScenarioOutline, b *gherkin.Backgrou
 
 func (s *Suite) runFeature(f *feature) {
 	s.fmt.Feature(f.Feature, f.Path, f.Content)
-	for _, scenario := range f.ScenarioDefinitions {
+
+	// make a local copy of the feature scenario defenitions,
+	// then shuffle it if we are randomizing scenarios
+	scenarios := make([]interface{}, len(f.ScenarioDefinitions))
+	if s.randomOrder {
+		perm := rand.Perm(len(f.ScenarioDefinitions))
+		for i, v := range perm {
+			scenarios[v] = f.ScenarioDefinitions[i]
+		}
+	} else {
+		copy(scenarios, f.ScenarioDefinitions)
+	}
+
+	for _, scenario := range scenarios {
 		var err error
 		if f.Background != nil {
 			s.fmt.Node(f.Background)