allow additional context initializers to be passed to SuiteContext

enables developers to inject extra context into the test environment
when running suites in meta-tests.

features/formatter/cucumber.feature

@@ -257,7 +257,7 @@ Feature: cucumber json formatter
                   "name": "passing step",
                   "line": 7,
                   "match": {
-                    "location": "suite_context.go:56"
+                    "location": "suite_context.go:67"
                   },
                   "result": {
                     "status": "passed",
@@ -269,7 +269,7 @@ Feature: cucumber json formatter
                   "name": "a failing step",
                   "line": 8,
                   "match": {
-                    "location": "suite_context.go:39"
+                    "location": "suite_context.go:50"
                   },
                   "result": {
                     "status": "failed",
@@ -325,7 +325,7 @@ Feature: cucumber json formatter
                   "name": "passing step",
                   "line": 11,
                   "match": {
-                    "location": "suite_context.go:56"
+                    "location": "suite_context.go:67"
                   },
                   "result": {
                     "status": "passed",
@@ -347,7 +347,7 @@ Feature: cucumber json formatter
                   "name": "failing step",
                   "line": 12,
                   "match": {
-                    "location": "suite_context.go:39"
+                    "location": "suite_context.go:50"
                   },
                   "result": {
                     "status": "failed",
@@ -448,7 +448,7 @@ Feature: cucumber json formatter
                   "line": 8
                 },
                 "match": {
-                  "location": "suite_context.go:56"
+                  "location": "suite_context.go:67"
                 },
                 "result": {
                   "status": "passed",
@@ -501,7 +501,7 @@ Feature: cucumber json formatter
                   "name": "passing step",
                   "line": 7,
                   "match": {
-                    "location": "suite_context.go:56"
+                    "location": "suite_context.go:67"
                   },
                   "result": {
                     "status": "passed",
@@ -535,7 +535,7 @@ Feature: cucumber json formatter
                   "name": "passing step",
                   "line": 10,
                   "match": {
-                    "location": "suite_context.go:56"
+                    "location": "suite_context.go:67"
                   },
                   "result": {
                     "status": "skipped"

suite_context.go

@@ -16,9 +16,20 @@ import (
 
 // SuiteContext can be used for meta-testing of godog features/steps themselves.
 //
-// For an example, see godog's own `features/` and `suite_test.go`.
-func SuiteContext(s *Suite) {
-	c := &suiteContext{}
+// A typical user of the godog library should never need this, rather it is
+// provided for those developing add-on libraries for godog.
+//
+// For an example of how to use, see godog's own `features/` and `suite_test.go`.
+func SuiteContext(s *Suite, additionalContextInitializers ...func(suite *Suite)) {
+	c := &suiteContext{
+		extraCIs: additionalContextInitializers,
+	}
+
+	// apply any additional context intializers to modify the context that the
+	// meta-tests will be run in
+	for _, ci := range additionalContextInitializers {
+		ci(s)
+	}
 
 	s.BeforeScenario(c.ResetBeforeEachScenario)
 
@@ -89,6 +100,7 @@ type firedEvent struct {
 type suiteContext struct {
 	paths       []string
 	testedSuite *Suite
+	extraCIs    []func(suite *Suite)
 	events      []*firedEvent
 	out         bytes.Buffer
 }
@@ -99,7 +111,7 @@ func (s *suiteContext) ResetBeforeEachScenario(interface{}) {
 	s.paths = []string{}
 	s.testedSuite = &Suite{}
 	// our tested suite will have the same context registered
-	SuiteContext(s.testedSuite)
+	SuiteContext(s.testedSuite, s.extraCIs...)
 	// reset all fired events
 	s.events = []*firedEvent{}
 }