From 53d2c477c606bcf91dacb4e2a520e1038b898935 Mon Sep 17 00:00:00 2001
From: tochemey <tochemey@hotmail.com>
Date: Sat, 7 Oct 2023 21:40:57 +0000
Subject: [PATCH] refactor: add unit test for entity

---
 engine.go      | 11 ++++++++++-
 entity.go      | 25 +++++++++++++++++++++++++
 entity_test.go | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 entity_test.go

diff --git a/engine.go b/engine.go
index 50b30c6..57866e5 100644
--- a/engine.go
+++ b/engine.go
@@ -24,6 +24,7 @@ type Engine struct {
 	discoveryConfig   discovery.Config       // discoveryConfig is the discovery provider config for clustering
 	telemetry         *telemetry.Telemetry   // telemetry is the observability engine
 	partitionsCount   uint64                 // partitionsCount specifies the number of partitions
+	started           atomic.Bool
 }
 
 // NewEngine creates an instance of Engine
@@ -40,6 +41,7 @@ func NewEngine(name string, eventsStore eventstore.EventsStore, opts ...Option)
 	for _, opt := range opts {
 		opt.Apply(e)
 	}
+	e.started.Store(false)
 	return e
 }
 
@@ -71,10 +73,17 @@ func (x *Engine) Start(ctx context.Context) error {
 		return err
 	}
 	// start the actor system
-	return x.actorSystem.Start(ctx)
+	if err := x.actorSystem.Start(ctx); err != nil {
+		return err
+	}
+	// set the started to true
+	x.started.Store(true)
+	return nil
 }
 
 // Stop stops the ego engine
 func (x *Engine) Stop(ctx context.Context) error {
+	// set the started to false
+	x.started.Store(false)
 	return x.actorSystem.Stop(ctx)
 }
diff --git a/entity.go b/entity.go
index 7ad02d1..0830a8b 100644
--- a/entity.go
+++ b/entity.go
@@ -10,6 +10,15 @@ import (
 	"github.com/tochemey/goakt/actors"
 )
 
+var (
+	// ErrEngineRequired is returned when the eGo engine is not set
+	ErrEngineRequired = errors.New("eGo engine is not defined")
+	// ErrEngineNotStarted is returned when the eGo engine has not started
+	ErrEngineNotStarted = errors.New("eGo engine has not started")
+	// ErrUndefinedEntity is returned when sending a command to an undefined entity
+	ErrUndefinedEntity = errors.New("eGo entity is not defined")
+)
+
 // Entity defines the event sourced persistent entity
 // This handles commands in order
 type Entity[T State] struct {
@@ -18,6 +27,15 @@ type Entity[T State] struct {
 
 // NewEntity creates an instance of Entity
 func NewEntity[T State](ctx context.Context, behavior EntityBehavior[T], engine *Engine) (*Entity[T], error) {
+	// check whether the ego engine is defined
+	if engine == nil {
+		return nil, ErrEngineRequired
+	}
+	// check whether the eGo engine has started or not
+	if !engine.started.Load() {
+		return nil, ErrEngineNotStarted
+	}
+
 	// create the instance of the actor
 	pid, err := engine.actorSystem.Spawn(ctx, behavior.ID(), newActor(behavior, engine.eventsStore))
 	// return the error in case there is one
@@ -34,7 +52,14 @@ func NewEntity[T State](ctx context.Context, behavior EntityBehavior[T], engine
 // 2. nil when there is no resulting state or no event persisted
 // 3. an error in case of error
 func (x Entity[T]) SendCommand(ctx context.Context, command Command) (resultingState T, revision uint64, err error) {
+	// define a nil state
 	var nilT T
+
+	// check whether the underlying actor is set and running
+	if x.actor == nil || !x.actor.IsRunning() {
+		return nilT, 0, ErrUndefinedEntity
+	}
+
 	// send the command to the actor
 	reply, err := actors.Ask(ctx, x.actor, command, time.Second)
 	// handle the error
diff --git a/entity_test.go b/entity_test.go
new file mode 100644
index 0000000..3b482f0
--- /dev/null
+++ b/entity_test.go
@@ -0,0 +1,49 @@
+package ego
+
+import (
+	"context"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/tochemey/ego/eventstore/memory"
+	samplepb "github.com/tochemey/ego/example/pbs/sample/pb/v1"
+)
+
+func TestNewEntity(t *testing.T) {
+	t.Run("With engine not defined", func(t *testing.T) {
+		ctx := context.TODO()
+		behavior := NewAccountBehavior(uuid.NewString())
+		// create an entity
+		entity, err := NewEntity[*samplepb.Account](ctx, behavior, nil)
+		require.Error(t, err)
+		require.Nil(t, entity)
+		assert.EqualError(t, err, ErrEngineRequired.Error())
+	})
+	t.Run("With engine not started", func(t *testing.T) {
+		ctx := context.TODO()
+		// create the event store
+		eventStore := memory.NewEventsStore()
+		// create the ego engine
+		engine := NewEngine("Sample", eventStore)
+		behavior := NewAccountBehavior(uuid.NewString())
+		// create an entity
+		entity, err := NewEntity[*samplepb.Account](ctx, behavior, engine)
+		require.Error(t, err)
+		require.Nil(t, entity)
+		assert.EqualError(t, err, ErrEngineNotStarted.Error())
+	})
+}
+
+func TestSendCommand(t *testing.T) {
+	t.Run("With entity not defined", func(t *testing.T) {
+		ctx := context.TODO()
+		entity := &Entity[*samplepb.Account]{}
+		resultingState, revision, err := entity.SendCommand(ctx, new(samplepb.CreateAccount))
+		require.Nil(t, resultingState)
+		require.Zero(t, revision)
+		require.Error(t, err)
+		assert.EqualError(t, err, ErrUndefinedEntity.Error())
+	})
+}