Dynamic Mock Enginer(DME): User & Technical Manual

1. Project Intent

The Mock Logic Controller (MLC) is a high-performance, lightweight Node.js middleware specifically engineered for performance testing tasks. It functions as a dynamic "Data and Fault Injection" hub to simulate external dependencies during load tests.

Key Performance Benefits:

• Zero-Bottleneck Architecture: Built on a non-blocking event loop to handle high-concurrency traffic.
• Low Memory Footprint: Uses in-memory Map lookups ($O(1)$ complexity) for instant response matching.
• Persistent Configuration: Automatically saves all mocks to mocks.json, ensuring your configurations survive server restarts.
• Real-Time Agility: Allows adding, cloning, or editing mocks without server restarts, preventing test downtime.

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2. Code Breakdown & Logic

Understanding the internal logic is vital for debugging during a performance run:

A. Persistence & Recovery

The server utilizes an auto-save mechanism. Every time a mock is added, edited, or removed, the saveToDisk() function updates mocks.json. Upon startup, loadFromDisk() restores your entire test suite.

B. Round-Robin Data Cycling

mock.currentIndex = (mock.currentIndex + 1) % mock.csvData.length; This logic uses the Modulo operator to ensure a continuous data loop. If headers in your CSV match keys in your Response JSON, the engine injects that row's data into the response.

C. Jitter & Latency Logic

The engine calculates a unique delay for every request to mimic "network noise":
$Delay = AvgDelay + (RandomJitter \times Deviation)$

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3. Deployment & Setup

Step 1: Folder Structure

Ensure your directory is organized as follows:

• /your-folder
  • server.js (The Engine)
  • package.json (Project Manifest)
  • mocks.json (Auto-generated backup)
  • key.pem & cert.pem (SSL Certificates)
  • /public/index.html (The Dashboard)
  • /data (Your uploaded CSV files)

Step 2: SSL Setup

Open your terminal in the project folder and run this to generate self-signed certificates for HTTPS:

openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -sha256 -days 365 -nodes -subj "/CN=localhost"

Step 3: Launch

1. Install requirements: Run npm install express express-fileupload csv-parse to ensure all middleware is available.
2. Start server: Execute node server.js or use npx nodemon server.js for development mode.
3. Open Dashboard: Navigate to http://localhost:3000 in your browser.

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4. Validation Test Cases (CURL)

Use these commands to validate your mock configuration, data cycling, and payload capture.

A. Validate Round-Robin (GET)

Run this command multiple times to verify that the response data cycles through your test.csv rows in a loop:

curl -i -k -X GET "https://localhost:3443/api/v1/validate-cycle"

Issue	Probable Cause	Fix / Solution
"Insecure" Error	Browser does not trust the self-signed certificates.	Click "Advanced" -> "Proceed" or use -k in your curl commands.
CSV Not Loading	The path is incorrect or the folder is missing.	Ensure the path starts with data/ and the file is in the correct folder.
High Latency	Mac CPU is throttled or in "Low Power Mode."	Plug in your Mac; Node.js needs CPU cycles for accurate jitter math.
Mock 404 Error	Case sensitivity or trailing slashes in the URL.	Ensure the UI registration path exactly matches your request URL.

5. Summary of Administrative URLs

1. UI Dashboard: http://localhost:3000.List
2. System Health: http://localhost:3000/_admin/health — Built-in check to validate connectivity.
3. Active Mocks: GET http://localhost:3000/_admin/list.Secure
4. Mock Endpoint: https://localhost:3443/[your-path].