curl -X POST https://api2.ecomailapp.cz/campaigns/1/send-test \
  -H "key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "emails": ["test@foo.cz", "qa@foo.cz"],
    "merge": {
      "first_name": "Foo"
    }
  }'

$campaignId = 1;
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://api2.ecomailapp.cz/campaigns/{$campaignId}/send-test");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode([
    'emails' => ['test@foo.cz', 'qa@foo.cz'],
    'merge' => [
        'first_name' => 'Foo',
    ],
]));
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'key: YOUR_API_KEY',
    'Content-Type: application/json',
]);
$response = curl_exec($ch);
curl_close($ch);

{
  "campaign_id": 1,
  "sent_emails_count": 2
}

{
  "errors": ["You can not do this because you have a blocked account"]
}

{
  "errors": ["Only draft campaigns can be tested."]
}

{
  "errors": {
    "emails": ["The emails field is required."]
  }
}

{
  "errors": ["You have exceeded daily limit of sent test emails of 50."]
}