test: test add and remove for lib/domain

test/parallel/test-domain-add-remove.js

@@ -0,0 +1,26 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const domain = require('domain');
+const EventEmitter = require('events');
+
+const d = new domain.Domain();
+const e = new EventEmitter();
+const e2 = new EventEmitter();
+
+d.add(e);
+assert.strictEqual(e.domain, d);
+
+// Adding the same event to a domain should not change the member count
+let previousMemberCount = d.members.length;
+d.add(e);
+assert.strictEqual(previousMemberCount, d.members.length);
+
+d.add(e2);
+assert.strictEqual(e2.domain, d);
+
+previousMemberCount = d.members.length;
+d.remove(e2);
+assert.notStrictEqual(e2.domain, d);
+assert.strictEqual(previousMemberCount - 1, d.members.length);