my ajax function somehow not covered by istanbul

[fikri2992]

I have a question I have this function

    authAnonymous: function (callback) {
    rest
      .post(wso2config.token.host + "/" + wso2config.token.path, {
        username: wso2config.clientId,
        password: wso2config.clientSecret,
        data: {
          username: wso2config.anonymousUser.username,
          password: wso2config.anonymousUser.password,
          grant_type: "password",
          redirect_uri: wso2config.redirect_uri,
          scope: "somescope:thisisit"
        }
      })
      .on("complete", function (data) {
        if (data.error) callback(data, null);
        else {
          data.anonym = true;
          callback(null, {
            openid_data: data
          });
        }
      });
  },

so i want to code coverage this function and i make some unit test using Jest here's the unit test code

test("do login using authAnonymous", done => {
  openID.authAnonymous(function (error, data) {
    if (!error) {
      expect(data.anonym).toBeTruthy();
    } else {
      //expect(data.anonym).toBe(false);
    }
  });
  done();
});

somehow this unit test is working as I expected but code coverage says the statement is not covered

this says the statement is not covered

as i understand my code works fine and unit test is working as expected why jest code coverage says this statement not covered can anyone explain how this statement covered works ? and why mine is not covered, i believe this is my fault but i don't know what to investigate here

--- update ---

this my silly mistake, it only needs to mock the post and chaining on function like this

  post: function() {
    return {
      on: function(event, callback) {
        callback('data', 'response');
      }
    }
  }
}