Hi,

The attached patch adds the module (ice-9 doctests) along with tests
(integrated into the test-suite) and texinfo documentation.

This provides doctests in the convenient style known from Python or
Haskell or jsdoc-tests or rustdoc tests - but without parsing strings,
so it does not inherit many of the problems in most other doctests.

A minimal looks like this:

    (define (tested-minimal)
      #((tests (test-equal #f (tested-with-doc))))
      #f)

This reduces the barrier to adopting test-driven-development, especially
for small procedures.

(ice-9 doctests) uses standard srfi-64 tests in the background, and it
does not aim to be a full replacement of all tests, but to reduce the
overhead for unit tests and to keep them close to the implementation.

Best wishes,
Arne