inAppBilling and phonegap

Question

I'm tryin to implement in-app Billing in my phonegap/cordova app and use this plugin: https://github.com/poiuytrez/AndroidInAppBilling

Code:

function successBy (data) {
  alert("by success")
  alert(data)
}
function failBy (data) {
  alert("by error")
  alert(data)
}
if ("inappbilling" in window) {
  inappbilling.init(function (data) {
    alert("init success")
    alert(data)
    inappbilling.buy(successBy, failBy, "android.test.purchased")
  }, function (err) {
    alert("init error")
    alert(err)
  });
}

confix.xml:

<gap:plugin name="com.smartmobilesoftware.inappbilling">
  <param name="BILLING_KEY" value="Here is my billing key..." />
</gap:plugin>

When i launch app, I got the init error alert with text

Failed to query inventory: labResult: Error refreshing inventory (querying owned 
items). (response: -1003: Purchase signature verification failed)

What am I doing wrong and how can I fix it?