fix flaky debug-logs test

Total luxury problem.  There are too many cores on my laptop, so
commands kick off and complete too quickly, resulting in not properly
demonstrating the behavior that this test is looking for.

test/tap/debug-logs.js

@@ -66,16 +66,28 @@ test('example', function (t) {
       t.matches(path.relative(cachedir, logfile), /^_logs/, 'debug log is inside the cache in _logs')
     }
 
-    // we run a bunch concurrently, this will actually create > than our limit as the check is done
-    // when the command starts
-    var todo = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
+    // we run a bunch concurrently, this will actually create > than our limit
+    // as the check is done when the command starts
+    //
+    // It has to be > the log count (10) but also significantly higher than
+    // the number of cores on the machine, or else some might be able to get
+    // to the log folder pruning logic in parallel, resulting in FEWER files
+    // than we expect being present at the end.
+    var procCount = Math.max(require('os').cpus().length * 2, 12)
+    var todo = new Array(procCount).join(',').split(',').map((v, k) => k)
     asyncMap(todo, function (num, next) {
+      // another way would be to just simulate this?
+      // var f = path.join(cachedir, '_logs', num + '-debug.log')
+      // require('fs').writeFile(f, 'log ' + num, next)
       common.npm(['run', '--logs-max=10', 'false'], conf, function (err, code) {
         if (err) throw err
         t.is(code, 1, 'run #' + num + ' errored as expected')
         next()
       })
     }, function () {
+      var files = glob.sync(path.join(cachedir, '_logs', '*'))
+      t.ok(files.length > 10, 'there should be more than 10 log files')
+
       // now we do one more and that should clean up the list
       common.npm(['run', '--logs-max=10', 'false'], conf, function (err, code) {
         if (err) throw err