Error encountered: Mocha - The property '$scope' cannot be read as it is undefined

I encountered an issue:

Error: Type Error - Cannot read property '$scope' of undefined
at $controller (angular/angular.js:10327:28)
at angular-mocks/angular-mocks.js:2221:12
at Context. (src/client/app/peer-review/post-visit.controller.spec.js:11:18)

This error occurs when conducting tests on an angularJS controller using mocha and karma.

The test initialization that triggers this error is as follows:

describe('PostVisitController', function () {
      var controller;

      beforeEach(function () {
        bard.appModule('app.peer-review');
        bard.inject('$controller', '$log');
        controller = $controller('PostVisitController');
      });

      bard.verifyNoOutstandingHttpRequests();

      it('should be created successfully', function () {
        expect(controller).to.be.defined;
      });
    });

Note: The controller being tested does not require $scope, and tests on other controllers within the same module are passing without any issues.

javascriptangularjskarma-mocha

Answer №1

This error message is deceiving.

During the instantiation of the controller in Angular, the code below is executed to verify if the controller is among the listed defined controllers:

    return function $controller(expression, locals, later, ident) {
      var instance, match, constructor, identifier;
      later = later === true;
      if (ident && isString(ident)) {
        identifier = ident;
      }

      if (isString(expression)) {
        match = expression.match(CNTRL_REG);
        if (!match) {
          throw $controllerMinErr('ctrlfmt',
            "Improperly formatted controller string '{0}'. " +
            "Must match `__name__ as __id__` or `__name__`.", expression);
        }
        constructor = match[1],
        identifier = identifier || match[3];
        expression = controllers.hasOwnProperty(constructor)  <———————— HERE
            ? controllers[constructor]
            : getter(locals.$scope, constructor, true) ||
                (globals ? getter($window, constructor, true) : undefined);

        assertArgFn(expression, constructor, true);
      }

If the controller is not found in the array, a getter is used which attempts to access $scope from the 'locals' variable (which may be null).

If the controller is missing from the array, it means it has not been included in the index file for your tests. Adding the file will fix the problem.

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