Writing a mock function for testing a login application - authentication

Question

I am making the authentication of my android application, I want to send the entered password & email in json format then my web service is going to test if they are correct then it will return the result in json format also.
But before doing this, I want to make a mock function that replace my webservice and do this just to test before .
Here is the code
After making the validation of interface(Email & password are valid )
mock class
if(fault==false)
//new AttemptLogin().execute();
new GetUser().execute();
My class GetUser is here (the mock class that will replace my web service )
private class GetUser extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Please wait...");
pDialog.setCancelable(false);
pDialog.show();
}
#Override
protected Void doInBackground(Void... arg0) {
String e2=email.getText().toString();
String p2=password.getText().toString();
if (e2 != null && p2!=null) {
try {
JSONObject jsonObj1 = new JSONObject(e2);
JSONObject jsonObj2 =new JSONObject(p2);
UserEmail=jsonObj1.getJSONObject(TAG_Email);
UserPassword=jsonObj2.getJSONObject(TAG_Password);
Toast.makeText(getApplicationContext(),"hi",
Toast.LENGTH_LONG).show();
String c=checkLogin(UserEmail, UserPassword);
Toast.makeText(getApplicationContext(),c,
Toast.LENGTH_LONG).show();
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
protected void onPostExecute(String result) {
// dismiss the dialog once product deleted
if (pDialog.isShowing())
pDialog.dismiss();
if (result != null){
Toast.makeText(MainActivity.this, result, Toast.LENGTH_LONG).show();
}
And this is the method checkLogin that check if the user has logged with the right email & password .
protected String checkLogin(JSONObject UserEmail,JSONObject UserPassword) {
String e ;
String p;
String r="";
try {
e= UserEmail.getString(TAG_Email);
p = UserPassword.getString(TAG_Password);
if (e.equals("exemple.android#yahoo.fr") &&
p.equals("123456")) {
Toast.makeText(getApplicationContext(), "Hello imene!",
Toast.LENGTH_SHORT).show();
r="ok";
} else {
Toast.makeText(getApplicationContext(), "Seems like you 're not imene!",
Toast.LENGTH_LONG).show();
numberOfRemainingLoginAttempts--;
Toast.makeText(getApplicationContext(), "number of Remaining login Attemts ="+numberOfRemainingLoginAttempts,
Toast.LENGTH_LONG).show();
if (numberOfRemainingLoginAttempts == 0) {
validate.setEnabled(false);
Toast.makeText(getApplicationContext(), "Login Locked!",
Toast.LENGTH_LONG).show();
r="ko";
}
}
} catch (JSONException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
return r;
}`
But ,i don't have any result .Can any one tell me where is the problem in my code .