Fix unit tests by updating domain and PHPUnit versions

[rmccue]

feelingrestful.com was decommissioned.

This should 🤞 fix the tests and allow other PRs to be merged.

[codecov-io]

Codecov Report

Merging #351 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #351   +/-   ##
=========================================
  Coverage     92.11%   92.11%           
  Complexity      760      760           
=========================================
  Files            21       21           
  Lines          1762     1762           
=========================================
  Hits           1623     1623           
  Misses          139      139

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[rmccue]

This should pass now, as all tests are passing except nightly (although it was incorrectly ignored previously). I've incorporated @datagutten's changes from #345 to fix the PHPUnit classes (thanks!).

Once that's done, @jrfnl's #346 should fix the failures on "nightly" (we're actually missing 7.3 as well; this will likely fix that too).

[rmccue]

Tests are now passing; I had to restart a couple due to the usual transient failures from external servers.

[rmccue]

Thanks @ntwb!