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
+}