feat: support --fake for aerich upgrade (#398)

* feat: support `--fake` for aerich upgrade

* Add `--fake` to downgrade

* tests: check --fake result for aerich upgrade and downgrade

* Update readme

* Fix unittest failed because of `db_field_types` changed

* refactor: improve type hints and document

conftest.py

@@ -1,27 +1,26 @@
 import asyncio
-import contextlib
 import os
 from typing import Generator
 
 import pytest
-from tortoise import Tortoise, expand_db_url, generate_schema_for_client
+from tortoise import Tortoise, expand_db_url
 from tortoise.backends.asyncpg.schema_generator import AsyncpgSchemaGenerator
 from tortoise.backends.mysql.schema_generator import MySQLSchemaGenerator
 from tortoise.backends.sqlite.schema_generator import SqliteSchemaGenerator
 from tortoise.contrib.test import MEMORY_SQLITE
-from tortoise.exceptions import DBConnectionError, OperationalError
 
 from aerich.ddl.mysql import MysqlDDL
 from aerich.ddl.postgres import PostgresDDL
 from aerich.ddl.sqlite import SqliteDDL
 from aerich.migrate import Migrate
+from tests._utils import init_db
 
 db_url = os.getenv("TEST_DB", MEMORY_SQLITE)
 db_url_second = os.getenv("TEST_DB_SECOND", MEMORY_SQLITE)
 tortoise_orm = {
     "connections": {
-        "default": expand_db_url(db_url, True),
-        "second": expand_db_url(db_url_second, True),
+        "default": expand_db_url(db_url, testing=True),
+        "second": expand_db_url(db_url_second, testing=True),
     },
     "apps": {
         "models": {"models": ["tests.models", "aerich.models"], "default_connection": "default"},
@@ -55,24 +54,7 @@ def event_loop() -> Generator:
 
 @pytest.fixture(scope="session", autouse=True)
 async def initialize_tests(event_loop, request) -> None:
-    # Placing init outside the try block since it doesn't
-    # establish connections to the DB eagerly.
-    await Tortoise.init(config=tortoise_orm)
-    with contextlib.suppress(DBConnectionError, OperationalError):
-        await Tortoise._drop_databases()
-    await Tortoise.init(config=tortoise_orm, _create_db=True)
-    try:
-        await generate_schema_for_client(Tortoise.get_connection("default"), safe=True)
-    except OperationalError as e:
-        if (s := "IF NOT EXISTS") not in str(e):
-            raise e
-        # MySQL does not support `CREATE INDEX IF NOT EXISTS` syntax
-        client = Tortoise.get_connection("default")
-        generator = client.schema_generator(client)
-        schema = generator.get_create_schema_sql(safe=True)
-        schema = schema.replace(f" INDEX {s}", " INDEX")
-        await generator.generate_from_string(schema)
-
+    await init_db(tortoise_orm)
     client = Tortoise.get_connection("default")
     if client.schema_generator is MySQLSchemaGenerator:
         Migrate.ddl = MysqlDDL(client)