fixed testing for lower versions of node

test/cli.js

@@ -1,18 +1,22 @@
 var test = require('tap').test
-var execSync = require('child_process').execSync
+var exec = require('child_process').exec
 
 test('the command line using pipes or arguments produces the same output', function (t) {
-  var exec = 'node ./bin/semver ';
-  [[exec+'-i 1.0.0', 'echo 1.0.0 | '+exec+'-i'],
-    [exec+'-i major 1.0.0', 'echo 1.0.0 | '+exec+'-i major'],
-    [exec+'-i prerelease 1.0.0', 'echo 1.0.0 | '+exec+'-i prerelease'],
-    [exec+'-i preminor 1.0.0', 'echo 1.0.0 | '+exec+'-i preminor'],
-    [exec+'-i prepatch --preid alpha 1.0.0', 'echo 1.0.0 | '+exec+'-i prepatch --preid alpha'],
-    [exec+'-r \\>1.0.0 0.8.0 1.1.1', 'echo 0.8.0 1.1.1 | '+exec+'-r \\>1.0.0']
+  t.plan(6);
+  var bin = 'node ./bin/semver ';
+  [[bin+'-i 1.0.0', 'echo 1.0.0 | '+bin+'-i'],
+    [bin+'-i major 1.0.0', 'echo 1.0.0 | '+bin+'-i major'],
+    [bin+'-i prerelease 1.0.0', 'echo 1.0.0 | '+bin+'-i prerelease'],
+    [bin+'-i preminor 1.0.0', 'echo 1.0.0 | '+bin+'-i preminor'],
+    [bin+'-i prepatch --preid alpha 1.0.0', 'echo 1.0.0 | '+bin+'-i prepatch --preid alpha'],
+    [bin+'-r \\>1.0.0 0.8.0 1.1.1', 'echo 0.8.0 1.1.1 | '+bin+'-r \\>1.0.0']
   ].forEach(function(tab) {
-    var resCli = execSync(tab[0]);
-    var resPipe = execSync(tab[1]);
-    t.assert(resCli.equals(resPipe));
+    exec(tab[0], function(error, stdout, stderr) {
+      var resCli = stdout + stderr;
+      exec(tab[1], function(error, stdout, stderr) {
+        var resPipe = stdout + stderr;
+        t.assert(resCli === resPipe);
+      });
+    });
   });
-  t.end()
 })