feat(backend): Migrate to vitest (#4296)

Author: jacekradko

.changeset/modern-chicken-crash.md

@@ -0,0 +1,2 @@
+---
+---

.vscode/launch.json

@@ -21,6 +21,19 @@
         "request": "launch",
         "command": "npm start",
         "cwd": "${workspaceFolder}/playground/express"
+      },
+      {
+        "name": "Debug Vitest",
+        "type": "node",
+        "request": "launch",
+        "program": "${workspaceFolder}/scripts/vitest-debug.mjs",
+        "args": ["${file}"],
+        "cwd": "${workspaceFolder}",
+        "console": "integratedTerminal",
+        "internalConsoleOptions": "neverOpen",
+        "autoAttachChildProcesses": true,
+        "smartStep": true,
+        "skipFiles": ["<node_internals>/**", "**/node_modules/**"]
       }
     ]
   }

docs/CONTRIBUTING.md

@@ -37,7 +37,6 @@ The current monorepo setup is based on:
 - [GitHub Actions](https://docs.github.com/en/actions), used for quality checks and automated release orchestration.
 - [Yalc](https://github.com/wclr/yalc), used for to publish packages locally and test them in other local projects.
 - [Jest](https://jestjs.io/), used for running unit tests.
-- [QUnit](https://qunitjs.com/), used for tests inside `@clerk/backend`.
 - [Playwright](https://playwright.dev/), used for running the [integration](../integration/) test suite.
 
 All packages of the monorepo are inside [packages](../packages). For package specific details on installation, architecture and usage, you can refer to the package's README file.