What do underscores in _servicename_ mean in AngularJS tests?

Question

In the following test example, the provider’s original name is APIEndpointProvider, but for the introduction of injections and maintenance, the agreement seems to be entered with underscores wrapping it. Why is this?

'use strict'; describe('Provider: APIEndpointProvider', function () { beforeEach(module('myApp.providers')); var APIEndpointProvider; beforeEach(inject(function(_APIEndpointProvider_) { APIEndpointProvider = _APIEndpointProvider_; })); it('should do something', function () { expect(!!APIEndpointProvider).toBe(true); }); }); 

What are the agreements? Am I missing a better explanation?

Answer 1

The underscore is a convenient trick that we can use to enter a service under a different name so that we can locally assign a local variable with the same name as the service.

That is, if we could not do this, we would need to use a different name for the local service:

 beforeEach(inject(function(APIEndpointProvider) { AEP = APIEndpointProvider; // <-- we can't use the same name! })); it('should do something', function () { expect(!!AEP).toBe(true); // <-- this is more confusing }); 

$injector used in testing can simply remove the underscores to provide us with the module we need. It does nothing but reuse the same name.

More details in Angular docs