fix: use explicit futuresMarket endpoint in shared WS functions and fix flaky checkFields test

Shared functions (candles, ticker, allTickers, aggTrades) now explicitly
route futures variator to endpoints.futuresMarket instead of relying on
endpoints.futures coincidentally pointing to /market/ws.

Also fix checkFields to use `field in object` instead of `t.truthy(value)`
so fields with valid falsy values like `trades: 0` don't cause failures.

Author: pcriadoperez

src/websocket.js

@@ -222,7 +222,11 @@ const candles = (payload, interval, cb, transform = true, variator) => {
     const cache = (Array.isArray(payload) ? payload : [payload]).map(symbol => {
         const w = openWebSocket(
             `${
-                variator ? endpoints[variator] : endpoints.base
+                variator === 'futures'
+                    ? endpoints.futuresMarket
+                    : variator === 'delivery'
+                      ? endpoints.delivery
+                      : endpoints.base
             }/${symbol.toLowerCase()}@kline_${interval}`,
         )
         w.onmessage = msg => {
@@ -378,7 +382,7 @@ const ticker = (payload, cb, transform = true, variator) => {
         const w = openWebSocket(
             `${
                 variator === 'futures'
-                    ? endpoints.futures
+                    ? endpoints.futuresMarket
                     : variator === 'delivery'
                       ? endpoints.delivery
                       : endpoints.base
@@ -411,7 +415,7 @@ const allTickers = (cb, transform = true, variator) => {
     const w = new openWebSocket(
         `${
             variator === 'futures'
-                ? endpoints.futures
+                ? endpoints.futuresMarket
                 : variator === 'delivery'
                   ? endpoints.delivery
                   : endpoints.base
@@ -561,7 +565,7 @@ const aggTrades = (payload, cb, transform = true, variator) => {
         const w = openWebSocket(
             `${
                 variator === 'futures'
-                    ? endpoints.futures
+                    ? endpoints.futuresMarket
                     : variator === 'delivery'
                       ? endpoints.delivery
                       : endpoints.base

test/utils.js

@@ -2,7 +2,7 @@ import http from 'http'
 
 export const checkFields = (t, object, fields) => {
     fields.forEach(field => {
-        t.truthy(object[field])
+        t.truthy(field in object)
     })
 }