test(services): add unit tests for getSendDelay rate-based logic

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: AchoArnold

api/pkg/services/message_service_test.go

@@ -0,0 +1,105 @@
+package services
+
+import (
+	"testing"
+	"time"
+
+	"github.com/NdoleStudio/httpsms/pkg/events"
+	"github.com/NdoleStudio/httpsms/pkg/telemetry"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"go.opentelemetry.io/otel/trace"
+)
+
+func TestGetSendDelay_WithSendAt_ReturnsTimeUntil(t *testing.T) {
+	service := &MessageService{}
+	logger := &noopLogger{}
+
+	sendAt := time.Now().UTC().Add(5 * time.Minute)
+	params := MessageSendParams{SendAt: &sendAt}
+	payload := events.MessageAPISentPayload{MessageID: uuid.New()}
+
+	delay := service.getSendDelay(logger, payload, params, 10)
+
+	// Should be approximately 5 minutes (within 2 seconds tolerance)
+	assert.InDelta(t, float64(5*time.Minute), float64(delay), float64(2*time.Second))
+}
+
+func TestGetSendDelay_WithSendAtInPast_ReturnsZero(t *testing.T) {
+	service := &MessageService{}
+	logger := &noopLogger{}
+
+	sendAt := time.Now().UTC().Add(-5 * time.Minute)
+	params := MessageSendParams{SendAt: &sendAt}
+	payload := events.MessageAPISentPayload{MessageID: uuid.New()}
+
+	delay := service.getSendDelay(logger, payload, params, 10)
+
+	assert.Equal(t, time.Duration(0), delay)
+}
+
+func TestGetSendDelay_BulkIndex_RateBasedDelay(t *testing.T) {
+	service := &MessageService{}
+	logger := &noopLogger{}
+
+	params := MessageSendParams{Index: 3}
+	payload := events.MessageAPISentPayload{MessageID: uuid.New()}
+
+	// 10 messages per minute = 6 seconds interval
+	delay := service.getSendDelay(logger, payload, params, 10)
+
+	expected := time.Duration(3) * (time.Minute / time.Duration(10))
+	assert.Equal(t, expected, delay)
+}
+
+func TestGetSendDelay_BulkIndex_ZeroRate_ReturnsZero(t *testing.T) {
+	service := &MessageService{}
+	logger := &noopLogger{}
+
+	params := MessageSendParams{Index: 5}
+	payload := events.MessageAPISentPayload{MessageID: uuid.New()}
+
+	delay := service.getSendDelay(logger, payload, params, 0)
+
+	assert.Equal(t, time.Duration(0), delay)
+}
+
+func TestGetSendDelay_IndexZero_ReturnsZero(t *testing.T) {
+	service := &MessageService{}
+	logger := &noopLogger{}
+
+	params := MessageSendParams{Index: 0}
+	payload := events.MessageAPISentPayload{MessageID: uuid.New()}
+
+	delay := service.getSendDelay(logger, payload, params, 10)
+
+	assert.Equal(t, time.Duration(0), delay)
+}
+
+func TestGetSendDelay_NoSendAtNoIndex_ReturnsZero(t *testing.T) {
+	service := &MessageService{}
+	logger := &noopLogger{}
+
+	params := MessageSendParams{}
+	payload := events.MessageAPISentPayload{MessageID: uuid.New()}
+
+	delay := service.getSendDelay(logger, payload, params, 10)
+
+	assert.Equal(t, time.Duration(0), delay)
+}
+
+// noopLogger implements telemetry.Logger for testing
+type noopLogger struct{}
+
+var _ telemetry.Logger = (*noopLogger)(nil)
+
+func (l *noopLogger) Error(_ error)                                 {}
+func (l *noopLogger) WithService(_ string) telemetry.Logger         { return l }
+func (l *noopLogger) WithString(_, _ string) telemetry.Logger       { return l }
+func (l *noopLogger) WithSpan(_ trace.SpanContext) telemetry.Logger { return l }
+func (l *noopLogger) Trace(_ string)                                {}
+func (l *noopLogger) Info(_ string)                                 {}
+func (l *noopLogger) Warn(_ error)                                  {}
+func (l *noopLogger) Debug(_ string)                                {}
+func (l *noopLogger) Fatal(_ error)                                 {}
+func (l *noopLogger) Printf(_ string, _ ...interface{})             {}