Set up comprehensive frontend testing infrastructure

- Install Jest for unit testing with React Testing Library
- Install Playwright for end-to-end testing
- Configure Jest with proper TypeScript support and module mapping
- Create test setup files and utilities for both unit and e2e tests

Components:
* Jest configuration with coverage thresholds
* Playwright configuration with browser automation
* Unit tests for LoginForm, AuthContext, and useSocketIO hook
* E2E tests for authentication, dashboard, and agents workflows
* GitHub Actions workflow for automated testing
* Mock data and API utilities for consistent testing
* Test documentation with best practices

Testing features:
- Unit tests with 70% coverage threshold
- E2E tests with API mocking and user journey testing
- CI/CD integration for automated test runs
- Cross-browser testing support with Playwright
- Authentication system testing end-to-end

🚀 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/node_modules/@sinonjs/commons/lib/value-to-string.test.js

@@ -0,0 +1,20 @@
+"use strict";
+
+var assert = require("@sinonjs/referee-sinon").assert;
+var valueToString = require("./value-to-string");
+
+describe("util/core/valueToString", function () {
+    it("returns string representation of an object", function () {
+        var obj = {};
+
+        assert.equals(valueToString(obj), obj.toString());
+    });
+
+    it("returns 'null' for literal null'", function () {
+        assert.equals(valueToString(null), "null");
+    });
+
+    it("returns 'undefined' for literal undefined", function () {
+        assert.equals(valueToString(undefined), "undefined");
+    });
+});