test(09-05): add failing tests for deterministic bulk delete

- Empty selections are 422 and duplicates run once in primary-key order
- A completed retry and an all-absent selection delete nothing and skip hooks
- Mixed, hook, cancel, and concurrent requests keep the batch atomic

cabana/crud_test.go

@@ -7,10 +7,10 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"strings"
+	"sync"
 	"testing"
-	"time"
-
 	"testing/fstest"
+	"time"
 
 	"gorm.io/gorm"
 )
@@ -118,10 +118,23 @@ func (r *crudRow) AfterUpdate(tx *gorm.DB) error {
 
 func (r *crudRow) BeforeDelete(tx *gorm.DB) error {
 	ctx := txContext(tx)
+	if _, ok := ctx.Value(bulkSlowKey{}).(bool); ok {
+		time.Sleep(300 * time.Millisecond)
+	}
 	recordHook(ctx, "before_delete")
+	appendDeletedID(ctx, r.ID)
 	if fail, _ := ctx.Value(failDeleteKey{}).(bool); fail {
 		return errors.New("secret-hook-boom")
 	}
+	if ids, ok := ctx.Value(failIDsKey{}).(map[uint]bool); ok && ids[r.ID] {
+		return errors.New("secret-hook-boom")
+	}
+	if id, ok := ctx.Value(cancelOnKey{}).(uint); ok && r.ID == id {
+		if cancel, ok := ctx.Value(cancelKey{}).(context.CancelFunc); ok {
+			cancel()
+		}
+		return context.Canceled
+	}
 	return nil
 }
 
@@ -132,6 +145,13 @@ func (r *crudRow) AfterDelete(tx *gorm.DB) error {
 
 type hookSinkKey struct{}
 type failDeleteKey struct{}
+type failIDsKey struct{}
+type idSinkKey struct{}
+type bulkSlowKey struct{}
+type cancelOnKey struct{}
+type cancelKey struct{}
+
+var hookMu sync.Mutex
 
 func txContext(tx *gorm.DB) context.Context {
 	if tx != nil && tx.Statement != nil && tx.Statement.Context != nil {
@@ -144,6 +164,8 @@ func recordHook(ctx context.Context, name string) {
 	if ctx == nil {
 		return
 	}
+	hookMu.Lock()
+	defer hookMu.Unlock()
 	sink, _ := ctx.Value(hookSinkKey{}).(*[]string)
 	if sink == nil {
 		return
@@ -151,6 +173,19 @@ func recordHook(ctx context.Context, name string) {
 	*sink = append(*sink, name)
 }
 
+func appendDeletedID(ctx context.Context, id uint) {
+	if ctx == nil {
+		return
+	}
+	hookMu.Lock()
+	defer hookMu.Unlock()
+	sink, _ := ctx.Value(idSinkKey{}).(*[]uint)
+	if sink == nil {
+		return
+	}
+	*sink = append(*sink, id)
+}
+
 type crudNoRules struct {
 	ID   uint   `gorm:"column:id;primaryKey"`
 	Name string `gorm:"column:name"`