[wp-trac] [WordPress Trac] #44351: Fix "Foreign key constraint is incorrectly formed" when running unit tests

[WordPress Trac]

#44351: Fix "Foreign key constraint is incorrectly formed" when running unit tests
------------------------------+-----------------------------
 Reporter:  conner_bw         |      Owner:  (none)
     Type:  enhancement       |     Status:  new
 Priority:  normal            |  Milestone:  Awaiting Review
Component:  Build/Test Tools  |    Version:  4.9.6
 Severity:  normal            |   Keywords:
  Focuses:                    |
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 I kept getting "Foreign key constraint is incorrectly formed" when running
 tests on my plugin. This drove me nuts for a few hours. The reason is
 [https://github.com/WordPress/wordpress-
 develop/blob/9e38c2847e5f3b94785378094d17f09577215d3c/tests/phpunit/includes/testcase.php#L335
 WP_UnitTestCase::start_transaction()]


 The WordPress testing framework changes all 'CREATE TABLE' queries to
 'CREATE TEMPORARY TABLE'.

 [https://dev.mysql.com/doc/refman/5.5/en/create-table-foreign-keys.html
 From the MYSQL manual]:

 > Foreign key relationships involve a parent table that holds the central
 data values, and a child table with identical values pointing back to its
 parent. The FOREIGN KEY clause is specified in the child table. The parent
 and child tables must use the same storage engine. **They must not be
 TEMPORARY tables**.

 Please add something like:

 {{{#!php
 <?php
 add_filter( 'query', [ $this, '_alter_temporary_tables' ] );
 // ... snip ...
 public function _alter_temporary_tables( $query ) {
     if ( 'ALTER TABLE' === substr( trim( $query ), 0, 11 ) && strpos(
 $query, 'ADD CONSTRAINT' ) !== false && strpos( $query, 'FOREIGN KEY' )
 !== false ) {
         return 'SELECT 1'; // Replace borken foreign key query with a fake
 query
     }
     return $query;
 }
 }}}

 To `WP_UnitTestCase::start_transaction()`

 Thank you for your consideration.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/44351>
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