How to do class mock, class apex and class test correctly ?

I consume a web servicio type REST.

1.- I create my class apex without fails.

2.- I create my class Test without fails, when execute the test it happen a fail with the web service.

3.- I create a class Mock but i thing is not correctly.

The Question is how to do relationship correctly between Class TEST and Class Mock ?

1.- This is Class Apex:
public static Map<String, Object> getEstatusSupPermanente(String accountId){
        String ctaFact;
        Map<String, Object> datos = new Map<String, Object>();
		datos.put('msj', 'OK');
        List<CuentaFactura__c> idBRM = [select Id, IdCuentaBRM__c from CuentaFactura__c where id = :accountId];
        for(CuentaFactura__c cf : idBRM){
            ctaFact = cf.IdCuentaBRM__c;
        }
        Http http = new Http();
        HttpRequest request = new HttpRequest();
        request.setEndpoint(EndPoint__c.getValues('StatusSupresionPermanente').URL__c);
        request.setMethod('POST');
        request.setHeader('Content-Type', 'application/json;charset=UTF-8');
        request.setHeader('Accept', 'application/json');
// Set the body as a JSON object
        request.setBody(datosCuenta);
        HttpResponse response;
        if (Test.isRunningTest()){
            Test.setMock(HttpCalloutMock.class, new movimientosCobranza_Mock());
            response = http.send(request);
        } else{
            response = http.send(request);
        }
        // PARSE THE JSON RESPONSE.
        if (response.getStatusCode() == 200) {
            datos = (Map<String, Object>)JSON.deserializeUntyped(response.getBody());
            List<Object> listax = (List<Object>) datos.get('ResponseBRM');
            datos.put('arreglo',listax[0]);
        } else {
            datos.put('msj', 'error');
            datos.put('response', response);
        }
        return datos;
    }
2.- This is Class Test:
        String idCtaFact;
        List<CuentaFactura__c> ctaFact = [SELECT Id, IdCuentaBRM__c FROM CuentaFactura__c LIMIT 1];
        for(CuentaFactura__c cf : ctaFact){
            idCtaFact = cf.Id;
        }
        Test.startTest();
        movimientosCobranza_CTRL.getEstatusSupPermanente(idCtaFact);
        Test.stopTest();
3.- This is Class Mock:
    global HTTPResponse respond(HTTPRequest request){
        String jsonTest = '{\n' +
            '"ResponseBRM":{\n' +
            '"AUTHORIZATION_ID":"SUSPO_A_X",\n' +
            '"VALUE":"1",\n' +
            '"CREATED_T":"2021-05-17T00:00:00"\n' +
            '},\n' +
            '}';
        HttpResponse response = new HttpResponse();
        response.setHeader('Content-Type', 'application/json');
        // response.setBody('{"ResponseBRM":"12345"}');
        response.setBody(jsonTest);
        response.setStatusCode(200);
        return response;
    }

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