improve tests of wallet
improve tests of wallet

MetacoSA/NBitcoin,NicolasDorier/NBitcoin,dangershony/NStratis,MetacoSA/NBitcoin,HermanSchoenfeld/NBitcoin,stratisproject/NStratis,thepunctuatedhorizon/BrickCoinAlpha.0.0.1,lontivero/NBitcoin,bitcoinbrisbane/NBitcoin