test: add test for workers thread-safety issues fix

Author: rmnilin

test/test-worker-imports.js

@@ -0,0 +1,19 @@
+// Test for thread-safety issues caused by subsequent imports of the module
+// in worker threads: https://github.com/mscdex/ssh2/issues/1393.
+// Each subsequent worker increases probability of abnormal termination.
+// The probability of a false pass due to zero response becomes negligible
+// for 4 consecutive workers.
+'use strict';
+
+const { Worker, isMainThread } = require('worker_threads');
+require('../lib/index.js');
+
+if (isMainThread) {
+  async function runWorker() {
+    return new Promise((r) => new Worker(__filename).on("exit", r));
+  }
+  runWorker()
+    .then(runWorker)
+    .then(runWorker)
+    .then(runWorker);
+}