Add -J|--jobs-auto to automatically calculate cores

This PR allows you to pass in -J which will automatically calculate the
number of cores using `os.cpus.length()`

Fixes: #342
Fixes: #344

bin/run.js

@@ -13,6 +13,7 @@ var osHomedir = require('os-homedir')
 var yaml = require('js-yaml')
 var path = require('path')
 var exists = require('fs-exists-cached').sync
+var os = require('os');
 
 var coverageServiceTest = process.env.COVERAGE_SERVICE_TEST === 'true'
 
@@ -158,6 +159,7 @@ function parseArgs (args, defaults) {
 
   var singleOpts = {
     j: 'jobs',
+    J: 'jobs-auto',
     R: 'reporter',
     t: 'timeout',
     s: 'save'
@@ -240,6 +242,11 @@ function parseArgs (args, defaults) {
         options.jobs = +val
         continue
 
+      case '--jobs-auto':
+        val = os.cpus().length;
+        options.jobs = +val
+        continue
+
       case '--coverage-report':
         options.coverageReport = val || args[++i]
         if (options.coverageReport === 'html')

bin/usage.txt

@@ -23,6 +23,12 @@ Options:
                               cannot be reported, and older TAP
                               parsers may get upset.
 
+  -J --jobs-auto              Run test files in parallel (auto calculated)
+                              Note that this causes tests to be run in
+                              "buffered" mode, so line-by-line results
+                              cannot be reported, and older TAP
+                              parsers may get upset.
+
   -c --color                  Use colors (Default for TTY)
 
   -C --no-color               Do not use colors (Default for non-TTY)

test/runner-jobs.js

@@ -0,0 +1,33 @@
+var t = require('../')
+var spawn = require('child_process').spawn
+var expect = {
+  jobs: require('os').cpus().length
+}
+var node = process.execPath
+var run = require.resolve('../bin/run.js')
+
+var args = [
+  ['-J'],
+  ['--jobs=99999', '-J'],
+  ['--jobs-auto'],
+  ['--jobs=99999', '--jobs-auto']
+]
+
+t.plan(args.length)
+
+args.forEach(function (arg) {
+  t.test(arg.join(' '), function (t) {
+    var child = spawn(node, [run, '-J', '--dump-config'])
+    var out = ''
+    child.stdout.on('data', function (c) {
+      out += c
+    })
+    child.on('close', function (code, signal) {
+      t.notOk(code)
+      t.notOk(signal)
+      t.match(JSON.parse(out), expect)
+      t.end()
+    })
+  })
+})
+