wp/tests/phpunit/tests/post/getLastPostDate.php

<?php

/**
 * @group post
 */
class Tests_Post_GetLastPostDate extends WP_UnitTestCase {

	/**
	 * @ticket 47777
	 */
	public function test_get_lastpostdate() {
		$post_post_date_first = '2020-01-30 16:09:28';
		$post_post_date_last  = '2020-02-28 16:09:28';

		$book_post_date_first = '2019-03-30 18:11:30';
		$book_post_date_last  = '2019-04-30 18:11:30';

		// Register book post type.
		register_post_type( 'book', array( 'has_archive' => true ) );

		// Create a simple post.
		$simple_post_id_first = self::factory()->post->create(
			array(
				'post_title' => 'Simple Post First',
				'post_type'  => 'post',
				'post_date'  => $post_post_date_first,
			)
		);

		$simple_post_id_last = self::factory()->post->create(
			array(
				'post_title' => 'Simple Post Last',
				'post_type'  => 'post',
				'post_date'  => $post_post_date_last,
			)
		);

		// Create custom type post.
		$book_cpt_id_first = self::factory()->post->create(
			array(
				'post_title' => 'Book CPT First',
				'post_type'  => 'book',
				'post_date'  => $book_post_date_first,
			)
		);

		$book_cpt_id_last = self::factory()->post->create(
			array(
				'post_title' => 'Book CPT Last',
				'post_type'  => 'book',
				'post_date'  => $book_post_date_last,
			)
		);

		$this->assertSame( $post_post_date_last, get_lastpostdate( 'blog', 'post' ) );
		$this->assertSame( $book_post_date_last, get_lastpostdate( 'blog', 'book' ) );
	}
}