Tests for supported Fortran features

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There is a proposal to add user-filterable tables to fortran-lang.org to show:

  1. The open/close code status
  2. Whether free / academic-free / paid
  3. Supported features (both standard and extensions)

and for tools, what they do - linter / formatter / migrator …

For the supported features we need lists of:

  1. The standard features which are not always fully supported
  2. The non-standard features which may not be supported

The proposal is to publish a simple test for each feature, and tests which stress the feature.
My question is which features should be tested?

For example, for non-standard features we could test:

%val
%ref
STRUCTURE/MAP/UNION
Embedded expressions in format specifications

Suggestions would be most welcome. So also would be test code!