Complete Guide to USSD Simulation and Testing | Free USSD Simulator

Request/Response Cycle

The simulator handles the complete request/response cycle:

// Initial Request
{
  "sessionId": "sim_abc123",
  "phoneNumber": "+233540000000",
  "text": "",
  "serviceCode": "*123#"
}

// Your Response
{
  "message": "Welcome\n1. Balance\n2. Transfer",
  "continueSession": true
}

// Next Request (user selected 1)
{
  "sessionId": "sim_abc123",
  "phoneNumber": "+233540000000",
  "text": "1",
  "serviceCode": "*123#"
}

Choosing the Right USSD Simulation Tool

Key Features to Look For

1. Multiple Gateway Formats: Support for Africa's Talking, Arkesel, Nalo, Wigal, and custom formats
2. Real-time Testing: Instant feedback as you interact with your app
3. Detailed Logging: View complete request/response history
4. Session Management: Proper handling of session state and timeouts
5. Network Simulation: Test different network operators
6. Easy Setup: No complex configuration required

USSD Playground: The Complete Solution

USSD Playground is a free, professional-grade USSD simulator that offers:

• ✅ Support for 7+ gateway formats
• ✅ Real-time phone emulator interface
• ✅ Comprehensive session logging
• ✅ Custom gateway builder for any provider
• ✅ No installation required - works in browser
• ✅ Free for unlimited testing

Setting Up Your First USSD Simulation

Step 1: Prepare Your Endpoint

Ensure your USSD endpoint is accessible. For local development:

• Use ngrok or similar tools to expose localhost
• Or deploy to a staging server
• Or use USSD Playground's test endpoint

Step 2: Configure Your Project

In USSD Playground:

1. Create a new project
2. Enter your endpoint URL
3. Set your USSD code (e.g., *123#)
4. Choose your gateway format
5. Select session mode (Implicit/Explicit/Hybrid)

Step 3: Start Testing

Use the phone emulator to:

1. Dial your USSD code
2. Navigate through menus
3. Test different user inputs
4. View real-time logs

Testing Different Session Scenarios

Happy Path Testing

Test the expected user journey:

• User dials code → sees main menu
• Selects option 1 → sees submenu
• Completes action → sees confirmation
• Session ends gracefully

Edge Case Testing

Test unusual scenarios:

• Invalid inputs: Letters when numbers expected
• Out of range: Selecting option 9 when only 1-3 exist
• Empty inputs: User presses send without typing
• Special characters: Testing with symbols
• Very long inputs: Testing character limits

Error Scenario Testing

Simulate error conditions:

• Endpoint unavailable (timeout)
• Invalid response format
• Server errors (500 status)
• Network interruptions

Simulating Multiple Networks

Different mobile networks may behave differently. Test with:

MTN

• Typically uses standard USSD format
• Session timeout: ~90 seconds
• Character limit: 182 characters

Vodafone

• May have different timeout settings
• Test with Vodafone-specific codes

AirtelTigo

• Verify compatibility with your gateway
• Test network-specific features

Debugging with Simulation Logs

Understanding Log Entries

Each log entry shows:

• Step Number: Position in the session flow
• Request Payload: What was sent to your endpoint
• Response Data: What your endpoint returned
• Timestamp: When the interaction occurred
• Session State: Whether session continues or ends

Common Issues and Solutions

Issue: Session ends unexpectedly
Solution: Check your continueSession flag or CON/END prefix

Issue: Menu not displaying correctly
Solution: Verify newline characters (\n) in your message

Issue: User input not received
Solution: Check sessionId consistency and text field parsing

Best Practices for USSD Simulation

1. Test Early, Test Often: Don't wait until deployment to start testing
2. Create Test Scenarios: Document common user flows and edge cases
3. Use Realistic Data: Test with actual phone numbers and realistic inputs
4. Monitor Session State: Verify session management at each step
5. Test Timeouts: Ensure your app handles session expiration gracefully
6. Validate All Inputs: Never trust user input - always validate
7. Test Error Handling: Verify your app recovers from errors properly
8. Check Character Limits: Ensure messages fit within 182 characters

Common Simulation Pitfalls

1. Not Testing Edge Cases

Don't just test the happy path. Users will do unexpected things.

2. Ignoring Session Timeouts

Real networks timeout after 30-90 seconds. Test this behavior.

3. Assuming Perfect Network

Networks can be slow or unreliable. Test with delays and errors.

4. Not Testing Different Devices

While simulators are great, occasional testing on real devices is valuable.

5. Skipping Load Testing

Your app might work for one user but fail under load.

Advanced Simulation Techniques

Automated Testing

Create automated test scripts that:

• Run through common user flows
• Verify expected responses
• Check for regressions
• Generate test reports

Load Testing

Simulate multiple concurrent users to:

• Identify performance bottlenecks
• Test session management under load
• Verify database connection pooling
• Ensure scalability

Integration Testing

Test your USSD app with:

• Payment gateways
• Database systems
• External APIs
• Third-party services

Using USSD Playground Simulator Features

Phone Emulator

Realistic phone interface that mimics actual USSD experience on mobile devices.

Session Logs

Detailed logs showing every request/response with expandable details.

Multiple Gateway Support

Test with different providers without changing your code.

Custom Gateway Builder

Configure custom request/response formats for any USSD provider.

Real-time Testing

See results instantly as you interact with your application.

Conclusion

USSD simulation is essential for efficient USSD development. By using a professional USSD simulator like USSD Playground, you can:

• Save time and money
• Test thoroughly before deployment
• Debug issues quickly
• Ensure quality user experience
• Deploy with confidence

Ready to start simulating? Try USSD Playground - the free, professional USSD simulator trusted by developers across Africa.