Task Description (Required)

https://github.com/redhat-ai-dev/model-catalog-template/pull/2 defines a way that the model catalog template (and other Backstage nunjucks templates) can be tested in a CI system.

Currently, the test code and associated helper functions, lay in the same file, "test.ts". Since we know that we will likely consume this test framework in other model catalog projects, as well as other nunjucks templates we maintain (e.g. https://github.com/redhat-ai-dev/ai-lab-app), extracting out the common test functions ("RenderTemplates", "TestFileMatchesTemplates"), as well as the model catalog specific functions ("TestModelCatalogDefaults", "TestModelCatalogTechdocs"), into their module might be useful.