In the new testing process, 4th option in the tools menu, now it is available a new test that checks if the example-normalized.jsonld is a valid NGSI LD file.
This process helps contributors to debug their data models before submit them officially (where there will be new tests before final approval)
The source code for the test is available at the repo.
Remember that if you want to improve / create a new test, just create a PR on the repo.