chore: tests for connection error handler

Author: himanshusinghs

src/mcp/mcpConnectionErrorHandler.ts

@@ -53,7 +53,7 @@ export const createMCPConnectionErrorHandler = (
             content: [
               {
                 type: 'text',
-                text: `MCP server is having trouble connecting to the ${activeConnectionName ?? 'selected connection in the MongoDB VSCode extension'}.`,
+                text: `MCP server is having trouble connecting to ${activeConnectionName ? activeConnectionName : 'the selected connection in the MongoDB VSCode extension'}.`,
               },
               ...resolutionGuidance.map<{ type: 'text'; text: string }>(
                 (text) => ({ type: 'text', text }),

src/mcp/mcpConnectionManager.ts

@@ -31,10 +31,10 @@ export class MCPConnectionManager extends ConnectionManager {
   connect(): Promise<AnyConnectionState> {
     return Promise.reject(
       new Error(
-        [
-          'MongoDB MCP Server in MongoDB VSCode extension makes use of the connection that the MongoDB VSCode extension is connected to.',
-          "To connect, choose a connection from MongoDB VSCode extensions's sidepanel - https://www.mongodb.com/docs/mongodb-vscode/connect/#connect-to-your-mongodb-deployment",
-        ].join(' '),
+        // MCP runs in node process
+        // eslint-disable-next-line no-multi-str
+        "MongoDB MCP Server in MongoDB VSCode extension makes use of the connection that the MongoDB VSCode extension is connected to.\
+        To connect, choose a connection from MongoDB VSCode extensions's sidepanel - https://www.mongodb.com/docs/mongodb-vscode/connect/#connect-to-your-mongodb-deployment",
       ),
     );
   }

src/test/suite/mcp/mcpConnectionErrorHandler.test.ts

@@ -0,0 +1,97 @@
+import sinon from 'sinon';
+import { expect } from 'chai';
+import { afterEach, beforeEach } from 'mocha';
+import { createMCPConnectionErrorHandler } from '../../../mcp/mcpConnectionErrorHandler';
+import ConnectionController from '../../../connectionController';
+import { ExtensionContextStub } from '../stubs';
+import { StorageController } from '../../../storage';
+import { TelemetryService } from '../../../telemetry';
+import { StatusView } from '../../../views';
+import type {
+  ConnectionErrorHandled,
+  ConnectionErrorHandlerContext,
+} from '@himanshusinghs/mongodb-mcp-server';
+import { ErrorCodes } from '@himanshusinghs/mongodb-mcp-server';
+
+class MongoDBError extends Error {
+  constructor(
+    public code:
+      | ErrorCodes.NotConnectedToMongoDB
+      | ErrorCodes.MisconfiguredConnectionString,
+    message: string,
+  ) {
+    super(message);
+  }
+}
+
+const sandbox = sinon.createSandbox();
+suite('mcpConnectionErrorHandler suite', () => {
+  let connectionController: ConnectionController;
+  beforeEach(() => {
+    const extensionContext = new ExtensionContextStub();
+    const testStorageController = new StorageController(extensionContext);
+    const testTelemetryService = new TelemetryService(
+      testStorageController,
+      extensionContext,
+    );
+    connectionController = new ConnectionController({
+      statusView: new StatusView(extensionContext),
+      storageController: testStorageController,
+      telemetryService: testTelemetryService,
+    });
+  });
+
+  afterEach(() => {
+    sandbox.reset();
+    sandbox.restore();
+  });
+
+  test('should handle NotConnectedToMongoDB error', () => {
+    const handler = createMCPConnectionErrorHandler(connectionController);
+    const result = handler(
+      new MongoDBError(
+        ErrorCodes.NotConnectedToMongoDB,
+        'Not connected to MongoDB',
+      ),
+      {} as ConnectionErrorHandlerContext,
+    ) as ConnectionErrorHandled;
+
+    expect(result.errorHandled).to.be.true;
+    expect(result.result.content).to.deep.contain({
+      type: 'text',
+      text: 'You need to connect to a MongoDB instance before you can access its data.',
+    });
+  });
+
+  test('should handle MisconfiguredConnectionString error', () => {
+    const handler = createMCPConnectionErrorHandler(connectionController);
+    const result = handler(
+      new MongoDBError(
+        ErrorCodes.MisconfiguredConnectionString,
+        'Misconfigured MongoDB string',
+      ),
+      {} as ConnectionErrorHandlerContext,
+    ) as ConnectionErrorHandled;
+
+    expect(result.errorHandled).to.be.true;
+    expect(result.result.content).to.deep.contain({
+      type: 'text',
+      text: 'MCP server is having trouble connecting to the selected connection in the MongoDB VSCode extension.',
+    });
+  });
+
+  test('should not handle any other errors', () => {
+    const handler = createMCPConnectionErrorHandler(connectionController);
+    expect(
+      handler(
+        new MongoDBError(ErrorCodes.ForbiddenCollscan as any, 'Some error'),
+        {} as any,
+      ),
+    ).to.deep.equal({
+      errorHandled: false,
+    });
+    expect(handler(new Error('Some error') as any, {} as any)).to.deep.equal({
+      errorHandled: false,
+    });
+  });
+});