diff --git a/djangochildformtest/child/child/__init__.py b/djangochildformtest/child/child/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/djangochildformtest/child/child/asgi.py b/djangochildformtest/child/child/asgi.py
new file mode 100644
index 0000000..dc6397a
--- /dev/null
+++ b/djangochildformtest/child/child/asgi.py
@@ -0,0 +1,16 @@
+"""
+ASGI config for child project.
+
+It exposes the ASGI callable as a module-level variable named ``application``.
+
+For more information on this file, see
+https://docs.djangoproject.com/en/4.2/howto/deployment/asgi/
+"""
+
+import os
+
+from django.core.asgi import get_asgi_application
+
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "child.settings")
+
+application = get_asgi_application()
diff --git a/djangochildformtest/child/child/settings.py b/djangochildformtest/child/child/settings.py
new file mode 100644
index 0000000..70b9dbc
--- /dev/null
+++ b/djangochildformtest/child/child/settings.py
@@ -0,0 +1,124 @@
+"""
+Django settings for child project.
+
+Generated by 'django-admin startproject' using Django 4.2.
+
+For more information on this file, see
+https://docs.djangoproject.com/en/4.2/topics/settings/
+
+For the full list of settings and their values, see
+https://docs.djangoproject.com/en/4.2/ref/settings/
+"""
+
+from pathlib import Path
+
+# Build paths inside the project like this: BASE_DIR / 'subdir'.
+BASE_DIR = Path(__file__).resolve().parent.parent
+
+
+# Quick-start development settings - unsuitable for production
+# See https://docs.djangoproject.com/en/4.2/howto/deployment/checklist/
+
+# SECURITY WARNING: keep the secret key used in production secret!
+SECRET_KEY = "django-insecure-b%&^(izms=udbncurdg-k75dui-414*-$y^z@f7huacb@ibs3l"
+
+# SECURITY WARNING: don't run with debug turned on in production!
+DEBUG = True
+
+ALLOWED_HOSTS = []
+
+
+# Application definition
+
+INSTALLED_APPS = [
+    "django.contrib.admin",
+    "django.contrib.auth",
+    "django.contrib.contenttypes",
+    "django.contrib.sessions",
+    "django.contrib.messages",
+    "django.contrib.staticfiles",
+    "validate"
+]
+
+MIDDLEWARE = [
+    "django.middleware.security.SecurityMiddleware",
+    "django.contrib.sessions.middleware.SessionMiddleware",
+    "django.middleware.common.CommonMiddleware",
+    "django.middleware.csrf.CsrfViewMiddleware",
+    "django.contrib.auth.middleware.AuthenticationMiddleware",
+    "django.contrib.messages.middleware.MessageMiddleware",
+    "django.middleware.clickjacking.XFrameOptionsMiddleware",
+]
+
+ROOT_URLCONF = "child.urls"
+
+TEMPLATES = [
+    {
+        "BACKEND": "django.template.backends.django.DjangoTemplates",
+        "DIRS": [],
+        "APP_DIRS": True,
+        "OPTIONS": {
+            "context_processors": [
+                "django.template.context_processors.debug",
+                "django.template.context_processors.request",
+                "django.contrib.auth.context_processors.auth",
+                "django.contrib.messages.context_processors.messages",
+            ],
+        },
+    },
+]
+
+WSGI_APPLICATION = "child.wsgi.application"
+
+
+# Database
+# https://docs.djangoproject.com/en/4.2/ref/settings/#databases
+
+DATABASES = {
+    "default": {
+        "ENGINE": "django.db.backends.sqlite3",
+        "NAME": BASE_DIR / "db.sqlite3",
+    }
+}
+
+
+# Password validation
+# https://docs.djangoproject.com/en/4.2/ref/settings/#auth-password-validators
+
+AUTH_PASSWORD_VALIDATORS = [
+    {
+        "NAME": "django.contrib.auth.password_validation.UserAttributeSimilarityValidator",
+    },
+    {
+        "NAME": "django.contrib.auth.password_validation.MinimumLengthValidator",
+    },
+    {
+        "NAME": "django.contrib.auth.password_validation.CommonPasswordValidator",
+    },
+    {
+        "NAME": "django.contrib.auth.password_validation.NumericPasswordValidator",
+    },
+]
+
+
+# Internationalization
+# https://docs.djangoproject.com/en/4.2/topics/i18n/
+
+LANGUAGE_CODE = "en-us"
+
+TIME_ZONE = "UTC"
+
+USE_I18N = True
+
+USE_TZ = True
+
+
+# Static files (CSS, JavaScript, Images)
+# https://docs.djangoproject.com/en/4.2/howto/static-files/
+
+STATIC_URL = "static/"
+
+# Default primary key field type
+# https://docs.djangoproject.com/en/4.2/ref/settings/#default-auto-field
+
+DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"
diff --git a/djangochildformtest/child/child/urls.py b/djangochildformtest/child/child/urls.py
new file mode 100644
index 0000000..c025ae3
--- /dev/null
+++ b/djangochildformtest/child/child/urls.py
@@ -0,0 +1,22 @@
+"""
+URL configuration for child project.
+
+The `urlpatterns` list routes URLs to views. For more information please see:
+    https://docs.djangoproject.com/en/4.2/topics/http/urls/
+Examples:
+Function views
+    1. Add an import:  from my_app import views
+    2. Add a URL to urlpatterns:  path('', views.home, name='home')
+Class-based views
+    1. Add an import:  from other_app.views import Home
+    2. Add a URL to urlpatterns:  path('', Home.as_view(), name='home')
+Including another URLconf
+    1. Import the include() function: from django.urls import include, path
+    2. Add a URL to urlpatterns:  path('blog/', include('blog.urls'))
+"""
+from django.contrib import admin
+from django.urls import path
+
+urlpatterns = [
+    path("admin/", admin.site.urls),
+]
diff --git a/djangochildformtest/child/child/wsgi.py b/djangochildformtest/child/child/wsgi.py
new file mode 100644
index 0000000..1594fed
--- /dev/null
+++ b/djangochildformtest/child/child/wsgi.py
@@ -0,0 +1,16 @@
+"""
+WSGI config for child project.
+
+It exposes the WSGI callable as a module-level variable named ``application``.
+
+For more information on this file, see
+https://docs.djangoproject.com/en/4.2/howto/deployment/wsgi/
+"""
+
+import os
+
+from django.core.wsgi import get_wsgi_application
+
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "child.settings")
+
+application = get_wsgi_application()
diff --git a/djangochildformtest/child/db.sqlite3 b/djangochildformtest/child/db.sqlite3
new file mode 100644
index 0000000..d69aa07
Binary files /dev/null and b/djangochildformtest/child/db.sqlite3 differ
diff --git a/djangochildformtest/child/manage.py b/djangochildformtest/child/manage.py
new file mode 100755
index 0000000..02eeb0d
--- /dev/null
+++ b/djangochildformtest/child/manage.py
@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+"""Django's command-line utility for administrative tasks."""
+import os
+import sys
+
+
+def main():
+    """Run administrative tasks."""
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "child.settings")
+    try:
+        from django.core.management import execute_from_command_line
+    except ImportError as exc:
+        raise ImportError(
+            "Couldn't import Django. Are you sure it's installed and "
+            "available on your PYTHONPATH environment variable? Did you "
+            "forget to activate a virtual environment?"
+        ) from exc
+    execute_from_command_line(sys.argv)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/djangochildformtest/child/validate/__init__.py b/djangochildformtest/child/validate/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/djangochildformtest/child/validate/admin.py b/djangochildformtest/child/validate/admin.py
new file mode 100644
index 0000000..0c47342
--- /dev/null
+++ b/djangochildformtest/child/validate/admin.py
@@ -0,0 +1,32 @@
+from django import forms
+from django.contrib import admin
+from django.core.exceptions import ValidationError
+
+from .models import Child
+from .models import Parent
+
+
+class ChildInlineFormset(forms.models.BaseInlineFormSet):
+    def clean(self):
+        sum = 0
+        for form in self.forms:
+            if (
+                form.is_valid()
+                and "proportion" in form.cleaned_data
+                and not form.cleaned_data["DELETE"]
+            ):
+                sum += form.cleaned_data["proportion"]
+        print(f">>> total proportion: {sum}")
+
+        if sum > 100:
+            raise ValidationError("Invalid proportion")
+
+
+class ChildAdmin(admin.TabularInline):
+    model = Child
+    formset = ChildInlineFormset
+
+
+@admin.register(Parent)
+class ParentAdmin(admin.ModelAdmin):
+    inlines = [ChildAdmin]
diff --git a/djangochildformtest/child/validate/apps.py b/djangochildformtest/child/validate/apps.py
new file mode 100644
index 0000000..4984cc1
--- /dev/null
+++ b/djangochildformtest/child/validate/apps.py
@@ -0,0 +1,6 @@
+from django.apps import AppConfig
+
+
+class ValidateConfig(AppConfig):
+    default_auto_field = "django.db.models.BigAutoField"
+    name = "validate"
diff --git a/djangochildformtest/child/validate/migrations/0001_initial.py b/djangochildformtest/child/validate/migrations/0001_initial.py
new file mode 100644
index 0000000..8452abc
--- /dev/null
+++ b/djangochildformtest/child/validate/migrations/0001_initial.py
@@ -0,0 +1,51 @@
+# Generated by Django 4.2 on 2023-04-25 18:14
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name="Parent",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("name", models.CharField(max_length=256)),
+            ],
+        ),
+        migrations.CreateModel(
+            name="Child",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("name", models.CharField(max_length=256)),
+                ("proportion", models.FloatField()),
+                (
+                    "parent",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        to="validate.parent",
+                    ),
+                ),
+            ],
+        ),
+    ]
diff --git a/djangochildformtest/child/validate/migrations/__init__.py b/djangochildformtest/child/validate/migrations/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/djangochildformtest/child/validate/models.py b/djangochildformtest/child/validate/models.py
new file mode 100644
index 0000000..3206936
--- /dev/null
+++ b/djangochildformtest/child/validate/models.py
@@ -0,0 +1,11 @@
+from django.db import models
+
+
+class Parent(models.Model):
+    name = models.CharField(max_length=256)
+
+
+class Child(models.Model):
+    name = models.CharField(max_length=256)
+    parent = models.ForeignKey(Parent, on_delete=models.CASCADE)
+    proportion = models.FloatField()
diff --git a/djangochildformtest/child/validate/tests.py b/djangochildformtest/child/validate/tests.py
new file mode 100644
index 0000000..7ce503c
--- /dev/null
+++ b/djangochildformtest/child/validate/tests.py
@@ -0,0 +1,3 @@
+from django.test import TestCase
+
+# Create your tests here.
diff --git a/djangochildformtest/child/validate/views.py b/djangochildformtest/child/validate/views.py
new file mode 100644
index 0000000..91ea44a
--- /dev/null
+++ b/djangochildformtest/child/validate/views.py
@@ -0,0 +1,3 @@
+from django.shortcuts import render
+
+# Create your views here.