How do I inject a controller into another controller in AngularJS

I'm new to Angular and trying to figure out how to do things...

Using AngularJS, how can I inject a controller to be used within another controller?

I have the following snippet:

var app = angular.module("testApp", ['']);

app.controller('TestCtrl1', ['$scope', function ($scope) {
    $scope.myMethod = function () {
        console.log("TestCtrl1 - myMethod");
    }
}]);

app.controller('TestCtrl2', ['$scope', 'TestCtrl1', function ($scope, TestCtrl1) {
    TestCtrl1.myMethod();
}]);

When I execute this, I get the error:

Error: [$injector:unpr] Unknown provider: TestCtrl1Provider <- TestCtrl1
http://errors.angularjs.org/1.2.21/$injector/unpr?p0=TestCtrl1Provider%20%3C-%20TestCtrl1

Should I even be trying to use a controller inside of another controller, or should I make this a service?