Define adapter interfaces and fake implementations

internal/adapters/notify/fake.go

@@ -0,0 +1,40 @@
+package notify
+
+import "context"
+
+// NoopSender is a deterministic no-op notifier.
+type NoopSender struct{}
+
+// Send returns a placeholder successful result.
+func (n *NoopSender) Send(ctx context.Context, _ SendRequest) (SendResult, error) {
+	if err := ctx.Err(); err != nil {
+		return SendResult{}, err
+	}
+	return SendResult{ProviderMessageID: "noop", Metadata: map[string]any{"placeholder": true}}, nil
+}
+
+// FakeSender captures send requests and returns deterministic responses.
+type FakeSender struct {
+	Requests []SendRequest
+	Err      error
+	Result   SendResult
+}
+
+// Send records request and returns configured response.
+func (f *FakeSender) Send(ctx context.Context, req SendRequest) (SendResult, error) {
+	if err := ctx.Err(); err != nil {
+		return SendResult{}, err
+	}
+	f.Requests = append(f.Requests, req)
+	if f.Err != nil {
+		return SendResult{}, f.Err
+	}
+	res := f.Result
+	if res.ProviderMessageID == "" {
+		res.ProviderMessageID = "fake"
+	}
+	if res.Metadata == nil {
+		res.Metadata = map[string]any{"fake": true}
+	}
+	return res, nil
+}

internal/adapters/notify/fake_test.go

@@ -0,0 +1,31 @@
+package notify
+
+import (
+	"context"
+	"errors"
+	"testing"
+)
+
+func TestFakeSenderCapturesRequestAndReturnsResult(t *testing.T) {
+	fake := &FakeSender{}
+	req := SendRequest{Subject: "done", Body: "body"}
+
+	res, err := fake.Send(context.Background(), req)
+	if err != nil {
+		t.Fatalf("Send() error = %v", err)
+	}
+	if len(fake.Requests) != 1 || fake.Requests[0].Subject != "done" {
+		t.Fatalf("requests = %#v, want captured request", fake.Requests)
+	}
+	if res.ProviderMessageID == "" {
+		t.Fatal("provider message id should be set")
+	}
+}
+
+func TestFakeSenderError(t *testing.T) {
+	fake := &FakeSender{Err: errors.New("boom")}
+	_, err := fake.Send(context.Background(), SendRequest{})
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}

internal/adapters/notify/sender.go

@@ -3,13 +3,20 @@ package notify
 
 import "context"
 
-// Sender is a placeholder adapter interface for notifications.
+// Sender is the adapter boundary for notifications.
 type Sender interface {
-	Send(ctx context.Context, msg Message) error
+	Send(ctx context.Context, req SendRequest) (SendResult, error)
 }
 
-// Message is a placeholder notification payload.
-type Message struct {
-	Subject string
-	Body    string
+// SendRequest describes one notification request.
+type SendRequest struct {
+	Subject  string
+	Body     string
+	Metadata map[string]string
+}
+
+// SendResult describes notification send outcome metadata.
+type SendResult struct {
+	ProviderMessageID string
+	Metadata          map[string]any
 }