Add end-to-end tests and improve unit test quality

.changeset/plain-hands-tap.md

@@ -0,0 +1,5 @@
+---
+'@storybook/addon-mcp': patch
+---
+
+improve handling of disableTelemetry option

.github/copilot-instructions.md

@@ -95,9 +95,26 @@ The `@storybook/mcp` package (in `packages/mcp`) is framework-agnostic:
 
 **Testing:**
 
-- Only `packages/mcp` has tests (Vitest with coverage)
-- Run `pnpm test run --coverage` in mcp package
-- Prefer TDD when adding new tools
+- **Unit tests**: Both `packages/mcp` and `packages/addon-mcp` have unit tests (Vitest with coverage)
+  - Run `pnpm test run --coverage` in individual package directories
+  - Run `pnpm test:run` at root to run all unit tests
+  - Prefer TDD when adding new tools
+- **E2E tests**: `apps/internal-storybook/tests` contains E2E tests for the addon
+  - Run `pnpm test` in `apps/internal-storybook` directory
+  - Tests verify MCP endpoint works with latest Storybook prereleases
+  - Uses inline snapshots for response validation
+  - **When to update E2E tests**:
+    - Adding or modifying MCP tools (update tool discovery snapshots)
+    - Changing MCP protocol implementation (update session init tests)
+    - Modifying tool responses or schemas (update tool-specific tests)
+    - Adding new toolsets or changing toolset behavior (update filtering tests)
+  - **Running tests**:
+    - `pnpm test` in apps/internal-storybook - run E2E tests
+    - `pnpm vitest run -u` - update snapshots when responses change
+    - Tests start Storybook server automatically, wait for MCP endpoint, then run
+  - **Test structure**:
+    - `mcp-endpoint.e2e.test.ts` - MCP protocol and tool tests
+    - `check-deps.e2e.test.ts` - Storybook version validation
 
 **Type checking:**
 

apps/internal-storybook/package.json

@@ -6,6 +6,7 @@
 	"scripts": {
 		"build-storybook": "storybook build",
 		"storybook": "storybook dev --port 6006 --loglevel debug --no-open",
+		"test": "cd ../.. && pnpm vitest --project=e2e",
 		"typecheck": "tsc"
 	},
 	"devDependencies": {
@@ -18,6 +19,7 @@
 		"react": "^18.2.0",
 		"react-dom": "^18.2.0",
 		"storybook": "catalog:",
+		"tinyexec": "^1.0.2",
 		"vite": "catalog:"
 	}
 }

apps/internal-storybook/tests/check-deps.e2e.test.ts

@@ -0,0 +1,55 @@
+import { describe, it } from 'vitest';
+import { x } from 'tinyexec';
+
+const PACKAGES_TO_CHECK = [
+	'@storybook/addon-docs',
+	'@storybook/react-vite',
+	'storybook',
+];
+
+describe('Storybook Dependencies', () => {
+	it('should be using latest versions from registry', async () => {
+		const outdated: Array<{ pkg: string; current: string; latest: string }> =
+			[];
+
+		for (const pkg of PACKAGES_TO_CHECK) {
+			// Get local version
+			const listResult = await x('pnpm', ['list', pkg, '--json'], {
+				nodeOptions: { cwd: process.cwd() },
+			});
+			const listData = JSON.parse(listResult.stdout);
+			const currentVersion =
+				listData[0]?.devDependencies?.[pkg]?.version ||
+				listData[0]?.dependencies?.[pkg]?.version;
+
+			if (!currentVersion) {
+				continue;
+			}
+
+			// Get registry version for @next tag
+			const viewResult = await x('pnpm', ['view', `${pkg}@next`, 'version'], {
+				nodeOptions: { cwd: process.cwd() },
+			});
+			const latestVersion = viewResult.stdout.trim();
+
+			// Compare versions
+			if (currentVersion !== latestVersion) {
+				outdated.push({ pkg, current: currentVersion, latest: latestVersion });
+			}
+		}
+
+		// If there are outdated packages, fail the test with instructions
+		if (outdated.length > 0) {
+			const outdatedList = outdated
+				.map(({ pkg, current, latest }) => `  - ${pkg}: ${current} → ${latest}`)
+				.join('\n');
+
+			const currentVersion = outdated[0]!.current.replace(/\./g, '\\.');
+			const latestVersion = outdated[0]!.latest;
+
+			throw new Error(
+				`Storybook dependencies are outdated. Update the catalog in pnpm-workspace.yaml:\n\n  sed -i '' 's/${currentVersion}/${latestVersion}/g' pnpm-workspace.yaml && pnpm install\n\nOutdated packages:\n${outdatedList}`,
+			);
+		}
+	});
+});