Add more tests and Take method

generics.go

@@ -49,6 +49,7 @@ type ExecInterface[T any] interface {
 	Scan(ctx context.Context, r interface{}) error
 	First(context.Context) (T, error)
 	Last(ctx context.Context) (T, error)
+	Take(context.Context) (T, error)
 	Find(ctx context.Context) ([]T, error)
 	FindInBatches(ctx context.Context, batchSize int, fc func(data []T, batch int) error) error
 	Row(ctx context.Context) *sql.Row
@@ -232,6 +233,12 @@ func (g *execG[T]) Last(ctx context.Context) (T, error) {
 	return r, err
 }
 
+func (g *execG[T]) Take(ctx context.Context) (T, error) {
+	var r T
+	err := g.g.db.WithContext(ctx).Take(&r).Error
+	return r, err
+}
+
 func (g *execG[T]) Find(ctx context.Context) ([]T, error) {
 	var r []T
 	err := g.g.db.WithContext(ctx).Find(&r).Error

tests/generics_test.go

@@ -3,6 +3,8 @@ package tests_test
 import (
 	"context"
 	"fmt"
+	"reflect"
+	"sort"
 	"testing"
 
 	"gorm.io/gorm"
@@ -28,6 +30,12 @@ func TestGenericsCreate(t *testing.T) {
 		t.Errorf("found invalid user, got %v, expect %v", u, user)
 	}
 
+	if u, err := gorm.G[User](DB).Where("name = ?", user.Name).Take(ctx); err != nil {
+		t.Fatalf("failed to find user, got error: %v", err)
+	} else if u.Name != user.Name || u.ID != user.ID {
+		t.Errorf("found invalid user, got %v, expect %v", u, user)
+	}
+
 	if u, err := gorm.G[User](DB).Select("name").Where("name = ?", user.Name).First(ctx); err != nil {
 		t.Fatalf("failed to find user, got error: %v", err)
 	} else if u.Name != user.Name || u.Age != 0 {
@@ -50,7 +58,7 @@ func TestGenericsCreate(t *testing.T) {
 		t.Errorf("found invalid user, got %v, expect %v", result, user)
 	}
 
-	mapResult, err := gorm.G[map[string]interface{}](DB).Table("users").Where("name = ?", user.Name).MapColumns(map[string]string{"name": "user_name"}).First(ctx)
+	mapResult, err := gorm.G[map[string]interface{}](DB).Table("users").Where("name = ?", user.Name).MapColumns(map[string]string{"name": "user_name"}).Take(ctx)
 	if v := mapResult["user_name"]; fmt.Sprint(v) != user.Name {
 		t.Errorf("failed to find map results, got %v", mapResult)
 	}
@@ -302,4 +310,58 @@ func TestGenericsJoinsAndPreload(t *testing.T) {
 	}
 }
 
-// Distinct, Group, Having
+func TestGenericsDistinct(t *testing.T) {
+	ctx := context.Background()
+
+	batch := []User{
+		{Name: "GenericsDistinctDup"},
+		{Name: "GenericsDistinctDup"},
+		{Name: "GenericsDistinctUnique"},
+	}
+	if err := gorm.G[User](DB).CreateInBatches(ctx, &batch, len(batch)); err != nil {
+		t.Fatalf("CreateInBatches failed: %v", err)
+	}
+
+	results, err := gorm.G[User](DB).Where("name like ?", "GenericsDistinct%").Distinct("name").Find(ctx)
+	if err != nil {
+		t.Fatalf("Distinct Find failed: %v", err)
+	}
+
+	if len(results) != 2 {
+		t.Errorf("expected 2 distinct names, got %d", len(results))
+	}
+
+	var names []string
+	for _, u := range results {
+		names = append(names, u.Name)
+	}
+	sort.Strings(names)
+	expected := []string{"GenericsDistinctDup", "GenericsDistinctUnique"}
+	if !reflect.DeepEqual(names, expected) {
+		t.Errorf("expected names %v, got %v", expected, names)
+	}
+}
+
+func TestGenericsGroupHaving(t *testing.T) {
+	ctx := context.Background()
+
+	batch := []User{
+		{Name: "GenericsGroupHavingMulti"},
+		{Name: "GenericsGroupHavingMulti"},
+		{Name: "GenericsGroupHavingSingle"},
+	}
+	if err := gorm.G[User](DB).CreateInBatches(ctx, &batch, len(batch)); err != nil {
+		t.Fatalf("CreateInBatches failed: %v", err)
+	}
+
+	grouped, err := gorm.G[User](DB).Where("name like ?", "GenericsGroupHaving%").Group("name").Having("COUNT(*) > ?", 1).Find(ctx)
+	if err != nil {
+		t.Fatalf("Group+Having Find failed: %v", err)
+	}
+
+	if len(grouped) != 1 {
+		t.Errorf("expected 1 group with count>1, got %d", len(grouped))
+	} else if grouped[0].Name != "GenericsGroupHavingMulti" {
+		t.Errorf("expected group name 'GenericsGroupHavingMulti', got '%s'", grouped[0].Name)
+	}
+}