setTestRtb method
Forces paid (RTB) recommendations into fetch responses, so the disclosure-icon handling can be tested without a live campaign. Process-wide; set it before fetch. Remove before release.
Requires TeadsSdk.setTestMode: native only sends the forced-RTB parameters while test mode is on, so without it this is silently a no-op. Verified on Android 6.2.2 and 6.2.3 (bytecode, and on an emulator); iOS gates it the same way per the SDK team, not re-verified here.
Set-only: Android's native setTestRTB has no getter.
Implementation
@override
Future<void> setTestRtb(bool enabled) async {
testRtb = enabled;
}