the module description of only the prod module. And the prod module doesn't inherit all
            the modules that the test module classes use, so we get errors.

            The good news is that, despite ignoring errors here, GWT does fail if any errors affect
            classes that are actually used in the module under test.

            Some tests need reflective access to the internals of these packages. It is only the
            tests themselves and not the code being tested that needs that access, though there's no
            obvious way to ensure that.

            We could consider arranging things so that only the tests we know need this would get
            the add-opens. Right now that doesn't seem worth the effort, though.
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