Tests recorded schema versions of early installed modules in the installer.
function testRequiredModuleSchemaVersions() {
$version = drupal_get_installed_schema_version('system', TRUE);
$this
->assertTrue($version > 0, 'System module version is > 0.');
$version = drupal_get_installed_schema_version('user', TRUE);
$this
->assertTrue($version > 0, 'User module version is > 0.');
}