During work on a legacy codebase I started to write some tests.
Tests run with an underlying sqlite-DB.
I've encountered a problem where an empty model-value could easily be stored by a MariaDB (Prod-ENV) or MySQL (Staging-ENV) while it failed when using the sqlite3 test-database.
As the tables are created from migrtions, the same configuration is used in all three systems:

Schema::create('consumers', function (Blueprint $table) {
  $table->bigIncrements('id');
  $table->integer('type');
  $table->string('name', 512);
  $table->string('xd_number', 512);
  $table->string('guid', 512);
  $table->string('country_iso', 2);
  $table->string('language_iso', 5);
  $table->string('software_version', 128)->nullable();
  $table->integer('online_count')->default(0);
  $table->integer('download_count')->default(0);
  $table->boolean('is_locked')->default(false);
  $table->timestamp('locked_at')->nullable();
  $table->timestamp('last_online_at')->nullable();
  $table->timestamps();
});

The php-code which "produces" the data which is then filled up whith "empty-strings" (maybe, from whatever) is this one:

$consumer = new Consumer();

$consumer->type = $data['type'];
$consumer->xd_number = $login;
$consumer->guid = $this->_createGuid();
$consumer->country_iso = $data['country_iso'];
$consumer->language_iso = $this->_getLanguageIso($request);
$consumer->software_version = $request->input('softwareVersion') ? $request->input('softwareVersion') : null;

$consumer->save();

So, this is a fresh instance of the Model and the name -property is never called.
I also tried to insert a record with PhpMyAdmin, leaving the name column empty although it is set as NOT NULL.
Even that worked as PhpMyAdmin shows the resulting query with all empty string-columns set to '' (empty string):

INSERT INTO `consumers` (`id`, `type`, `name`, `xd_number`, `guid`, `country_iso`, `language_iso`, `software_version`, `online_count`, `download_count`, `is_locked`, `locked_at`, `last_online_at`, `auth_response`, `created_at`, `updated_at`)  
VALUES (NULL, '1', '', '', '', '', '', NULL, '0', '0', '0', NULL, NULL, NULL, NULL, NULL);

A model-property which is not set returns, as a normal php class property, NULL when called.
Am I guessing right, that this means, the NULL -value is turned into '' during the save? Probably by the database?
What do I miss, that MySQL and MariaDB both replace NULL by '' but SQLite tries to insert NULL into this column and complains about the integrity constraint violation?

Integrity constraint violation:  
19 NOT NULL constraint failed: consumers.name

insert into "consumers" ("type", "xd_number", "guid", "country_iso", "language_iso", "software_version", "updated_at", "created_at")  
values (1, FooBar, da55d74c10e1eb31503ec96767268cd0, DE, de-DE, ?, 2022-08-31 00:30:17, 2022-08-31 00:30:17)