feat: add unit test framework

.github/workflows/code_health.yaml

@@ -19,3 +19,17 @@ jobs:
               run: npm ci
             - name: Run style check
               run: npm run check
+
+    run-tests:
+        runs-on: ubuntu-latest
+        steps:
+            - uses: GitHubSecurityLab/actions-permissions/monitor@v1
+            - uses: actions/checkout@v4
+            - uses: actions/setup-node@v4
+              with:
+                  node-version-file: package.json
+                  cache: "npm"
+            - name: Install dependencies
+              run: npm ci
+            - name: Run tests
+              run: npm test

CONTRIBUTING.md

@@ -57,6 +57,25 @@ This project implements a Model Context Protocol (MCP) server for MongoDB and Mo
 
 4. Commit your changes with a descriptive commit message
 
+## Adding tests to the MCP Server
+
+When adding new features or fixing bugs, please ensure that you also add tests to cover your changes. This helps maintain the quality and reliability of the codebase.
+
+## Running Tests
+
+The tests can be found in the `__tests__` directory.
+
+You can run tests using the following npm scripts:
+
+- `npm test`: Run all tests
+
+To run a specific test file or directory:
+
+```bash
+npm test -- path/to/test/file.test.ts
+npm test -- path/to/directory
+```
+
 ## Troubleshooting
 
 ### Restart Server

__tests__/unit/index.test.ts

@@ -0,0 +1,27 @@
+import { describe, it } from "@jest/globals";
+import { runServer } from "../../src/index";
+import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio";
+
+// mock the StdioServerTransport
+jest.mock("@modelcontextprotocol/sdk/server/stdio");
+// mock Server class and its methods
+jest.mock("../../src/server.ts", () => {
+    return {
+        Server: jest.fn().mockImplementation(() => {
+            return {
+                connect: jest.fn().mockImplementation((transport) => {
+                    return new Promise((resolve) => {
+                        resolve(transport);
+                    });
+                }),
+            };
+        }),
+    };
+});
+
+describe("Server initialization", () => {
+    it("should create a server instance", async () => {
+        await runServer();
+        expect(StdioServerTransport).toHaveBeenCalled();
+    });
+});

jest.config.js

@@ -0,0 +1,19 @@
+/** @type {import('ts-jest').JestConfigWithTsJest} **/
+export default {
+    preset: "ts-jest/presets/default-esm",
+    testEnvironment: "node",
+    extensionsToTreatAsEsm: [".ts"],
+    moduleNameMapper: {
+        "^(\\.{1,2}/.*)\\.js$": "$1", // Map .js to real paths for ESM
+    },
+    transform: {
+        "^.+\\.tsx?$": [
+            "ts-jest",
+            {
+                useESM: true,
+                tsconfig: "tsconfig.jest.json", // Use specific tsconfig file for Jest
+            },
+        ],
+    },
+    moduleFileExtensions: ["ts", "tsx", "js", "jsx", "json", "node"],
+};