Try and clean up a failed primary instance creation

pkg/game/world.go

@@ -47,6 +47,16 @@ func (w *World) CreateInstance() uuid.UUID {
 	return id
 }
 
+// Removes an instance from the game
+func (w *World) DestroyInstance(id uuid.UUID) error {
+	if _, ok := w.Instances[id]; ok {
+		delete(w.Instances, id)
+	} else {
+		return fmt.Errorf("no instance matching id")
+	}
+	return nil
+}
+
 // GetPosition returns the position of a given instance
 func (w World) GetPosition(id uuid.UUID) (Position, error) {
 	if i, ok := w.Instances[id]; ok {

pkg/game/world_test.go

@@ -2,6 +2,8 @@ package game
 
 import (
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestNewWorld(t *testing.T) {
@@ -24,3 +26,19 @@ func TestWorld_CreateInstance(t *testing.T) {
 		t.Errorf("Incorrect number of instances created")
 	}
 }
+
+func TestWorld_DestroyInstance(t *testing.T) {
+	world := NewWorld()
+	a := world.CreateInstance()
+	b := world.CreateInstance()
+
+	err := world.DestroyInstance(a)
+	assert.NoError(t, err, "Error returned from instance destroy")
+
+	// Basic duplicate check
+	if len(world.Instances) != 1 {
+		t.Error("Too many instances left in world")
+	} else if _, ok := world.Instances[b]; !ok {
+		t.Error("Remaining instance is incorrect")
+	}
+}