public function testGetRegionCodesForCountryCode()
{
$regionCodesForNANPA = $this->phoneUtil->getRegionCodesForCountryCode(1);
$this->assertContains(RegionCode::US, $regionCodesForNANPA);
$this->assertContains(RegionCode::BS, $regionCodesForNANPA);
$this->assertContains(RegionCode::GB, $this->phoneUtil->getRegionCodesForCountryCode(44));
$this->assertContains(RegionCode::DE, $this->phoneUtil->getRegionCodesForCountryCode(49));
$this->assertContains(RegionCode::UN001, $this->phoneUtil->getRegionCodesForCountryCode(800));
// Test with invalid country calling code.
$this->assertEmpty($this->phoneUtil->getRegionCodesForCountryCode(-1));
}