Unit testing with get request

Question

I am trying to create a unit test for one of my api.

In the frontend, I send it this way...

params = {
    participants: JSON.stringify(participants),
    section: JSON.stringify(section),
};
axios.get('/api/list', params)

while in the controller, it receives the params this way...

public function list(Request $request)
{
    $participants = json_decode($request->participants);
    $section = json_decode($request->section);

}

Now, I tried making a unit test out of this. by doing...

$params = [
    'participants' => ['id', 'name', 'rating'],
    'section' => ['id', 'code'],
];

$this->get('/api/list'.http_build_query($params))->assertStatus(200)
// $this->json('/api/list', $params)->assertStatus(200) // -> also tried this one
// $this->getJson('/api/list', $params)->assertStatus(200) // -> also tried this one
// $this->call('GET', '/api/list', $params)->assertStatus(200) // -> also tried this one

But none of them works, it always says TypeError: json_decode(): Argument #1 ($json) must be of type string, array given.

So, the way I built the url and the params must be all wrong,

so my question here is that, what's the correct way of building the url so that it provides a correct url string format and the controller will json_decode the params?