switch Random opt from bool to int64

This allows for us to propagate the seed value around, and not have to
have two different values in Options when we want to allow
specification of seed.  It does introduce some “magic values”, but the
document them in the Options struct docstrings.

options.go

@@ -13,12 +13,17 @@ type Options struct {
 	// Print step definitions found and exit
 	ShowStepDefinitions bool
 
-	// Run scenarios in random order.
+	// RandomSeed, if not `0`, will be used to run scenarios in a 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
+	// Randomizing scenario order is especially helpful for detecting
+	// situations where you have state leaking between scenarios, which can
+	// cause flickering or fragile tests.
+	//
+	// The default value of `0` means "do not randomize".
+	//
+	// The magic value of `-1` means "pick a random seed for me", the resulting
+	// seed will only be between `1-99999` for ease of specification.
+	RandomSeed int64
 
 	// Stops on the first failure
 	StopOnFailure bool

run.go

@@ -13,7 +13,7 @@ import (
 type initializer func(*Suite)
 
 type runner struct {
-	randomOrder   bool
+	randomSeed    int64
 	stopOnFailure bool
 	features      []*feature
 	fmt           Formatter
@@ -33,7 +33,7 @@ func (r *runner) concurrent(rate int) (failed bool) {
 			}
 			suite := &Suite{
 				fmt:           r.fmt,
-				randomOrder:   r.randomOrder,
+				randomSeed:    r.randomSeed,
 				stopOnFailure: r.stopOnFailure,
 				features:      []*feature{feat},
 			}
@@ -58,7 +58,7 @@ func (r *runner) concurrent(rate int) (failed bool) {
 func (r *runner) run() (failed bool) {
 	suite := &Suite{
 		fmt:           r.fmt,
-		randomOrder:   r.randomOrder,
+		randomSeed:    r.randomSeed,
 		stopOnFailure: r.stopOnFailure,
 		features:      r.features,
 	}
@@ -111,20 +111,26 @@ func RunWithOptions(suite string, contextInitializer func(suite *Suite), opt Opt
 	features, err := parseFeatures(opt.Tags, opt.Paths)
 	fatal(err)
 
+	seed := opt.RandomSeed
+	if seed == -1 {
+		// if RandomSeed opt is -1, means pick a memorable rand seed as default
+		// the docStrings for Option specify this should be 1-99999 (same as ruby Cucumber)
+		r := rand.New(rand.NewSource(time.Now().UTC().UnixNano()))
+		seed = r.Int63n(99998) + 1
+	}
+	if seed != 0 {
+		// init global rand module (concurrent safe) with our seed
+		rand.Seed(seed)
+	}
+
 	r := runner{
 		fmt:           formatter(suite, output),
 		initializer:   contextInitializer,
 		features:      features,
-		randomOrder:   opt.RandomOrder,
+		randomSeed:    seed,
 		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

@@ -50,7 +50,7 @@ type Suite struct {
 	fmt      Formatter
 
 	failed        bool
-	randomOrder   bool
+	randomSeed    int64
 	stopOnFailure bool
 
 	// suite event handlers
@@ -336,7 +336,7 @@ func (s *Suite) runFeature(f *feature) {
 	// 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 {
+	if s.randomSeed != 0 {
 		perm := rand.Perm(len(f.ScenarioDefinitions))
 		for i, v := range perm {
 			scenarios[v] = f.ScenarioDefinitions[i]