public class BankServiceTest{
  [Fact]
  public void GetBanks_Should_ReturnBankList()
  {
      //Arrange
      var bank = new Bank();
      bankId = 1;
      var service = new BankServices();

      //Act
      var sut = service.GetBank(bank);

      //Assert
      Assert.True(sut.Id = bank.Id);
  }
}

public class BankServices{
  public Bank GetBank(Bank bank)
  {
    return _context.Banks.FirstOrDefault(x => x.Id = bank.Id);
  }
}