Support custom properties file formats in `@TestPropertySource`

[sbrannen]

Overview

In Spring Framework 4.3, we introduced the PropertySourceFactory SPI for use with @PropertySource. This issue aims to introduce the same support in @TestPropertySource.

Related Issues

• Allow the use of custom PropertySource annotations in @Configuration classes [SPR-8963] #13603
• Improve @PropertySource loading support [SPR-12116] #16732
• Add support for property file encoding in @TestPropertySource #30982
• @TestPropertySource not recognizing yaml files spring-boot#33434

[snicoll]

Reopening as the deprecation of MergedContextConfiguration#getPropertySourceLocations requires to use MergedContextConfiguration#getPropertySourceDescriptors which doesn't have any equivalent in TestPropertySourceUtils.

There is a method that could work but it's private at the moment.