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AssertNoUniqueTextRector

Fixes deprecated AssertLegacyTrait::assertNoUniqueText() calls

-$this->assertNoUniqueText('Duplicated message');
+$page_text = $this->getSession()->getPage()->getText();
+$nr_found = substr_count($page_text, 'Duplicated message');
+$this->assertGreaterThan(1, $nr_found, "'Duplicated message' found more than once on the page");

Configure your rector.php:

<?php

use DrupalRector\Drupal9\Rector\Deprecation\AssertNoUniqueTextRector;
use Rector\Config\RectorConfig;

return RectorConfig::configure()
    ->withRules([
        AssertNoUniqueTextRector::class,
    ]);