public function testGetEmailWhenBillingAddressNotExist()
 {
     $quoteMock = $this->getMock('Magento\\Quote\\Model\\Quote', [], [], '', false);
     $quoteMock->expects($this->once())->method('getBillingAddress')->willReturn(null);
     $this->model->setQuote($quoteMock);
     $this->assertEquals('', $this->model->getEmail());
 }