Calls text_summary() and asserts that the expected teaser is returned.
function callTextSummary($text, $expected, $format = NULL, $size = NULL) {
$summary = text_summary($text, $format, $size);
$this
->assertIdentical($summary, $expected, t('Generated summary "@summary" matches expected "@expected".', array(
'@summary' => $summary,
'@expected' => $expected,
)));
}