spawn: emit a 'skip' for tests that do nothing

Author: isaacs

lib/test.js

@@ -494,8 +494,15 @@ Test.prototype.spawn = function spawnTest (cmd, args, options, name, extra) {
     bailOnFail(this, child.stdout, parser)
 
   child.stdout.emit('data', '# Subtest: ' + name + '\n')
+  var sawOutput = false
+  child.stdout.once('data', function () {
+    sawOutput = true
+  })
 
   child.stdout.on('end', function () {
+    // if there's been literally no output, then emit the minimum viable tap
+    if (!sawOutput)
+      child.stdout.emit('data', '1..0\n')
     parser.end()
   })
 
@@ -517,14 +524,18 @@ Test.prototype.spawn = function spawnTest (cmd, args, options, name, extra) {
     extra.results = results
     var dur = process.hrtime(start)
     var time = Math.round(dur[0] * 1e6 + dur[1] / 1e3) / 1e3
-    name += ' # time=' + time + 'ms'
     if (code)
       extra.exitCode = code
     if (signal)
       extra.signal = signal
     extra.command = cmd
     extra.arguments = args
 
+    if (results.count === 0)
+      extra.skip = 'No tests found'
+    else
+      name += ' # time=' + time + 'ms'
+
     self.ok(results.ok && !code, name, extra)
     if (!self._ended)
       self.push('\n')

test/test/spawn-empty.js

@@ -0,0 +1,5 @@
+if (process.argv[2] === 'child')
+  return
+
+var t = require('../..')
+t.spawn(process.execPath, [__filename, 'child'])

test/test/spawn-empty.tap

@@ -0,0 +1,8 @@
+TAP version 13
+    # Subtest: ___/.*/~~~spawn-empty.js child
+    1..0
+ok 1 - ___/.*/~~~spawn-empty.js child # SKIP No tests found
+
+1..1
+___/# time=[0-9.]+(ms)?/~~~
+