diff --git a/tests/phpunit/tests/functions/WpMysqlWeek.php b/tests/phpunit/tests/functions/WpMysqlWeek.php
new file mode 100644
index 0000000000000..7fc33fa30060f
--- /dev/null
+++ b/tests/phpunit/tests/functions/WpMysqlWeek.php
@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * Tests for the _wp_mysql_week function.
+ *
+ * @group Functons.php
+ *
+ * @covers ::_wp_mysql_week
+ */
+class Tests_Functons_WpMysqlWeek extends WP_UnitTestCase {
+
+	/**
+	 * @ticket 59931
+	 *
+	 * @dataProvider data_test_wp_mysql_week
+	 */
+	public function test_wp_mysql_week( $date, $start_of_week, $expected_sql ) {
+
+		add_filter(
+			'pre_option_start_of_week',
+			static function ( $value ) use ( $start_of_week ) {
+				return $start_of_week ?? $value;
+			}
+		);
+
+		$this->assertSame( $expected_sql, _wp_mysql_week( 'col_name' ) );
+	}
+
+	/**
+	 * @return array[]
+	 */
+	public function data_test_wp_mysql_week() {
+		return array(
+			array( '1969-12-25', 0, 'WEEK( col_name, 0 )' ),
+			array( '1969-12-25', 1, 'WEEK( col_name, 1 )' ),
+			array( '1969-12-25', 2, 'WEEK( DATE_SUB( col_name, INTERVAL 2 DAY ), 0 )' ),
+			array( '1969-12-25', 3, 'WEEK( DATE_SUB( col_name, INTERVAL 3 DAY ), 0 )' ),
+			array( '1969-12-25', 4, 'WEEK( DATE_SUB( col_name, INTERVAL 4 DAY ), 0 )' ),
+			array( '1969-12-25', 5, 'WEEK( DATE_SUB( col_name, INTERVAL 5 DAY ), 0 )' ),
+			array( '1969-12-25', 6, 'WEEK( DATE_SUB( col_name, INTERVAL 6 DAY ), 0 )' ),
+			array( '1969-12-25', 9, 'WEEK( col_name, 0 )' ),
+		);
+	}
+}