Test support package version 1.3.0 was released.

New version adds implementation of PSR logger that accumulates all the logged messages and can return these as array:

$logger = new Yiisoft\Test\Support\Log\SimpleLogger();

$logger->emergency('Emergency message', ['key' => 'value']);
$logger->alert('Alert message', ['key' => 'value']);
$logger->critical('Critical message', ['key' => 'value']);
$logger->error('Error message', ['key' => 'value']);
$logger->warning('Warning message', ['key' => 'value']);
$logger->notice('Notice message', ['key' => 'value']);
$logger->info('Info message', ['key' => 'value']);
$logger->debug('Debug message', ['key' => 'value']);

$messages = $logger->getMessages();