Add stdin test

test/cli.js

@@ -2,6 +2,7 @@ var path   = require('path'),
     assert = require('assert'),
     fs     = require('fs'),
     exec   = require('child_process').exec,
+    spawn  = require('child_process').spawn,
     assign = require('object-assign'),
     cli    = process.env.NODESASS_COVERAGE ? require('../lib-coverage/cli') : require('../lib/cli'),
     cliPath = path.resolve(__dirname, '../bin/node-sass'),
@@ -32,6 +33,19 @@ var sampleCssOutputPath = path.join(__dirname, '../sample.css');
 var sampleCssMapOutputPath = path.join(__dirname, '../sample.css.map');
 
 describe('cli', function() {
+  it('should read data from stdin', function(done) {
+    var src = fs.createReadStream(sampleScssPath);
+    var emitter = spawn(cliPath, ['--stdout']);
+
+    emitter.stdout.on('data', function(data) {
+      data = data.toString().trim();
+      assert.equal(data, expectedSampleNoComments.trim());
+      done();
+    });
+
+    src.pipe(emitter.stdin);
+  });
+
   it('should print help when run with no arguments', function(done) {
     var env = assign(process.env, { isTTY: true });
     exec('node ' + cliPath, {