/**
     * Got EPC token and ret as global variables;
     */
    var res = JSON.parse(responseBody);

    pm.globals.set("apiToken", res.egPrincipalToken);
    pm.globals.set("egPrincipalToken", res.egPrincipalToken);
    console.log(res);   

    //  assert test
    pm.test("api response test", function() {
        console.log("aaa");
        pm.expect(pm.response.text()).to.include("apiToken");
        pm.expect(pm.response.text()).to.include("egPrincipalToken");
    })

Refer: https://www.cnblogs.com/ZhengYing0813/p/11693785.html