title: Is there a way to make testthat search recursively?
body: <p>When my R package directory structure has R files directly in the tests folder</p>
  
  <pre><code>.
  +--Projroot
  +---- R
  |     -- routine1.R
  |     -- routine2.R
  +---- tests
        -- test_routine1.R
        -- test_routine2.R
  </code></pre>
  
  <p><code>testthat</code> catches the <code>test_*.R</code> files, but when the tests themselves depend on a multitude of files, it's cleaner to have test subdirectories</p>
  
  <pre><code>.
  +--Projroot
  +---- R
  |     -- routine1.R
  |     -- routine2.R
  +---- tests
        |
        +---- test_routine1
        |     -- test_routine1.R
        |     -- help_file11
        |     -- help_file12
        +---- test_routine2
              -- test_routine2.R
              -- help_file21
              -- help_file22
  </code></pre>
  
  <p>Just running <code>devtools::test()</code> does not catch the <code>test_*.R</code> files in inner directories.</p>
  
  <p>Is there a way to make <code>testthat</code> search recursively?</p>