sample.js

  var runCommand       = require('../helpers/run-command');
  var childProcess = require('child_process');
  
  function ifHasGit(callback) {
    return new Promise(function(resolve) {
      childProcess.exec('git --version', function(error){
        if (!!error) {
          callback();
        }
      })
    })
  }
  it('calls git init when git is present', function() {
    return ifHasGit(function(){
      // do your actual assertions here
    })
  });