instantiate required controller using $controller service

var tms2 = angular.module('tms2', ['tms_sub']);
    tms2.controller("mCtrl", ["$scope","$controller", function ($scope,$controller) {
    var mainCtrl =  $controller('mainCtrl');
    $scope.test = "a1";
    $scope.testClick = function () {
        mainCtrl.testClick1();
       }
    }]);

Tip: Create separate service for common methods and inject it on both controllers.

Tip: Create separate service for common methods and inject into both controllers.