[REQ] Auto generated test samples, unit test, integration test

Is your feature request related to a problem? Please describe.

We would like to auto generate tests from open API specs. I can see there testCase holder in this test API file : https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/python/api_test.handlebars#L40
but it is not clear how this works.

I found in the code https://github.com/OpenAPITools/openapi-generator/blob/574a70c3152a6d137db37f4df908fc824d733cc5/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java#L95 that this may come from x-schema-test-examples but it is not clear how to add this to open API yaml

Could please add some example of open API specs that allow tests generation or explain this in the documentation

Describe the solution you'd like

Describe alternatives you've considered

Additional context

Start with modules/openapi-generator/src/main/resources/python/api_test.handlebars and the referenced DefaultCodegen.java location to understand how x-schema-test-examples is consumed. Add an OpenAPI specification example or documentation showing how to define these examples for generated unit and integration tests, and verify that the explanation matches the existing generation behavior.