multiple arguments and implementation

[satheesh6789]

I have the requirement in feature file as below,

Given User launches application
And User verifies "" "" displayed successfully

Examples:
| firstname | lastname |
| JOHN| SMITH |

in step-definition file:
Then(/^User verifies "([^"])" "([^"])" displayed successfully$/,firstname,lastname =>{
return client
.assert.containsText('/body',firstname)
}

getting below error:
eferenceError: firstname is not defined
at Object. (C:\Users\Desktop\nightwatch\step-definitions\UserApp_CreateNewAppAndVerify.js:189:71)