There really isn't actually a "test" for severe depression or any other kind of depression. Those tests are designed by statisticians, and statistics can prove anything you want them to. They are a tool, but only a tool. Anyone who has taken a basic statistics course finds those tests obvious and laughable. I know, I've taken my share, and there's nobody on Earth who couldn't be diagnosed with a mental illness if those tests were what we went by. Severe depression is diagnosed by how you're feeling. If you are obsessed with depressed thinking, you're depressed. If you're not, you aren't. Sadness and grief and general malaise aren't depression. You don't say how you're feeling, but if you truly feel you are depressed the person to see for diagnosis is a psychologist. They study the most psychology. If they think you're too depressed for therapy they will refer you to a psychiatrist, who can also diagnose depression but again, they study a lot less psychology than a psychologist does. So while you can't self-diagnose, you can see someone who can.
I'm just speaking as a parent, here. Forget about the online tests, or any "test" for that matter. Try approaching your parents, or at least the one you're closest to, and tell them you're concerned that you might be struggling with depression and you feel like you need to talk to a counselor. Telling them how you feel, and what you're experiencing, is going to be a lot more personal and persuasive than the results of an online test.
If you absolutely cannot talk to your parents, talk to another trusted adult - another relative, a teacher, a school nurse/counselor - who can point you in the right direction. Hiding your problems from your parents isn't going to help you get the treatment you may need, in the long run. If you do have depression, you are going to want and need your parents to be partners with you in your treatment.
You could always tell them that you'd like to speak with a counselor about bad feelings you've been having. Personally, I wouldn't try to hide it from them. That puts more stress on yourself, and your parents can help support you in this if you let them know.
Hi there. I have a son that I worry about, also a teen. I understand. It's hard. But a parents job is to help you. Sometimes our own fear and whatnot will make us react in strange ways but ultimately, your parents will want to help you. I look at depression like this, it's something anyone can have from time to time. We all get in a funk or the blues. But if it is lasting for days and days and really impacting things OR if you have any thoughts of harming yourself in any way, then it is time to seek help. They do give you questionnaires that you may be terming test as part of the diagnostic procedure. You could do one online to see if you are checking boxes but just know that when a doctor does it, it is just part of the protocol and they are trained to read them accurately and use the information to help you. We don't want to self treat or self diagnose! Therapists can be really helpful at your age. They listen, they offer suggestions, they tell you when things are at a point of needing to move to adding in other treatment options like medicine. So, please talk to your parents, one or both. And hopefully this will get better soon. I tell my son baby steps still move you forward.