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Trackly SMS does not have a sandbox or test mode — all API calls send real messages. Use these practices to test safely and cost-effectively.

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Use Your Own Numbers

Send test messages to phone numbers you control. This lets you verify delivery, formatting, and opt-out handling without affecting real contacts. 
curl -X POST https://app.tracklysms.com/api/v2/send \
  -H "X-Api-Key: trk_your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "+1YOUR_OWN_NUMBER",
    "list_number": "+18005551234",
    "body": "Test message from integration. Ref: {{messageId}}"
  }'

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Leverage the Free Tier

Every account includes 500 free messages per month. Use this allowance for integration testing before committing to paid volume.

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Create Dedicated Test API Keys

Generate a separate API key for testing in Dashboard > Settings > API Keys. Label it clearly (e.g., “Development - Test Only”). This makes it easy to:
  • Revoke test keys without affecting production
  • Track test usage separately in billing
  • Prevent accidental production sends from development environments

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Test Opt-Out Flow

Verify that STOP keyword handling works correctly:
  1. Send a test message to your own number
  2. Reply with STOP
  3. Confirm the contact is marked as unsubscribed in the dashboard
  4. Attempt to send another message — it should be blocked
  5. Reply with START to re-subscribe (if your account supports it)

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Test Webhooks

Use a webhook inspection tool to verify event delivery before building your handler:
  1. Set up a temporary endpoint using a service like webhook.site or RequestBin
  2. Configure the URL in Dashboard > Settings > Webhooks
  3. Send a test message and verify you receive the delivery event
  4. Check that the X-Trackly-Signature header is present
Then implement your handler and verify signature verification works: 
import hmac
import hashlib

def verify_webhook(payload_body, signature_header, webhook_secret):
    expected = hmac.new(
        webhook_secret.encode(),
        payload_body,
        hashlib.sha256
    ).hexdigest()
    return hmac.compare_digest(f"sha256={expected}", signature_header)

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Test Bulk Operations

Start with small batches before scaling up:
  1. 5 contacts — verify the request format and response structure
  2. 50 contacts — check partial failure handling (include one invalid number)
  3. 500 contacts — validate performance and error handling at moderate scale
import requests

# Test with a small batch including one invalid number
response = requests.post(
    "https://app.tracklysms.com/api/v2/send/bulk",
    headers={"X-Api-Key": "trk_your_test_key"},
    json={
        "list_number": "+18005551234",
        "messages": [
            {"to": "+1YOUR_NUMBER", "body": "Test 1"},
            {"to": "invalid_number", "body": "Test 2"},  # Expect this to fail
        ]
    }
)

data = response.json()
print(f"Queued: {data['queued_count']}, Errors: {data['error_count']}")
print(f"Error details: {data.get('errors', [])}")

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Test Checklist

  • Single message sends and receives successfully
  • Bulk send handles partial failures correctly
  • Webhook events are received and verified
  • STOP keyword triggers unsubscribe
  • Error responses are parsed and handled
  • Transient error (5xx) retry logic works
  • Link tracking redirects correctly (if using offers)
  • Contact creation and journey enrollment works

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Next Steps

Going to Production

Launch your integration

Error Codes

Handle all error scenarios