Using HttpAgent for sending request to PicJs Server

I'm developing this standard ICRC-112.

I want to send a request from client to PicJS server when I run unit test

This is my code

const agent = await HttpAgent.create({ host: process.env.PIC_URL });

The error I got

 The canister call cannot be executed: AgentHTTPResponseError [AgentError]: Server returned an error:
        Code: 404 (Not Found)
        Body: 

The reason I ask this because I want to test making canister call as a signer to canister while testing

Signer have to send this kind of request to canister instead using actor

   {
          "canisterId": "eeddf-fqaaa-aaaao-a2hlq-ca",
          "method": "icrc2_approve",
          "arg": "RElETARte24AbAKzsNrDA2ithsqDBQFsA/vKAQKi3pTrBgHYo4yoDX0BAwEdV+ztKgq7E4l1ffuTuwEmw8AtYSjlrJ+WLO5ofQIAAMgB"
        }

Start by reviewing the HttpAgent.create call using process.env.PIC_URL and the unit-test scenario described in the issue. Reproduce the 404 from the PicJS server, then compare the intended signer request with the shown canister-call JSON. Done means the request path and expected testing approach are established or the issue is documented as unsupported.