import { writeFileSync, readFileSync, existsSync, mkdirSync } from 'fs';
import { join, dirname } from 'path';
import { expect } from 'vitest';
/**
* Snapshot testing for tool schemas
* Prevents unintended changes to MCP tool definitions
*/
export async function snapshotTest(
toolName: string,
toolDefinition: any,
snapshotDir: string = '__snapshots__'
): Promise<void> {
const snapshotPath = join(
process.cwd(),
'test',
snapshotDir,
`${toolName}.json`
);
const shouldUpdate = process.env.UPDATE_SNAPSHOTS === 'true';
// Ensure snapshot directory exists
if (!existsSync(dirname(snapshotPath))) {
mkdirSync(dirname(snapshotPath), { recursive: true });
}
// Serialize tool definition (excluding function, only schema)
const schemaOnly = {
name: toolDefinition.name,
title: toolDefinition.title,
description: toolDefinition.description,
scopes: toolDefinition.scopes,
inputSchema: toolDefinition.inputSchema,
};
const currentSnapshot = JSON.stringify(schemaOnly, null, 2);
// Update mode: overwrite snapshot
if (shouldUpdate) {
writeFileSync(snapshotPath, currentSnapshot, 'utf-8');
console.log(`✓ Updated snapshot for ${toolName}`);
return;
}
// Test mode: compare against saved snapshot
if (!existsSync(snapshotPath)) {
throw new Error(
`Snapshot not found for ${toolName}.\n` +
`Run: UPDATE_SNAPSHOTS=true npm test`
);
}
const savedSnapshot = readFileSync(snapshotPath, 'utf-8');
expect(currentSnapshot).toBe(savedSnapshot);
}
