tests: add a test for closing a channel with LND

Not sure if we should add this as the Dispose() method
of the test class actually:
https://stackoverflow.com/a/33516224/544947

tests/CommonTests.cs

@@ -536,5 +536,26 @@ public void CanParseLightningURL()
 			Assert.True(LightningConnectionString.TryParse("type=charge;server=http://api-token:[email protected]:54938/;allowinsecure=true", out conn));
 			Assert.Equal("type=charge;server=http://127.0.0.1:54938/;api-token=foiewnccewuify;allowinsecure=true", conn.ToString());
 		}
+
+		[Fact(Timeout = Timeout)]
+		public async Task CanCloseLndChannel()
+		{
+			// TODO: test in all LN implementations, not just LND
+			//foreach (var test in Tester.GetTestedPairs())
+			//{
+				var test = Tester.GetTestedLndPair();
+				await EnsureConnectedToDestinations(test);
+				var customer = (ILightningClient)test.Customer;
+				var senderChannel = (await customer.ListChannels()).First();
+
+				var senderInfo = await customer.GetInfo();
+				var closeChannelRequest = new CloseChannelRequest()
+				{
+					NodeInfo = senderInfo.NodeInfoList.First(),
+					ChannelPointOutputIndex = senderChannel.ChannelPoint.N
+				};
+				await test.Merchant.CloseChannel(closeChannelRequest, CancellationToken.None);
+			//}
+		}
 	}
 }

tests/Tester.cs

@@ -87,11 +87,18 @@ public static LndClient CreateLndClientDest()
 			yield return ("Eclair (Client)", CreateEclairClient());
 		}
 
+		private static (string Name, ILightningClient Customer, ILightningClient Merchant) GetTestedCLightningPair()
+			=> ("C-Lightning", CreateCLightningClient(), CreateCLightningClientDest());
+		internal static (string Name, LndClient Customer, LndClient Merchant) GetTestedLndPair()
+			=> ("LND", CreateLndClient(), CreateLndClientDest());
+		private static (string Name, ILightningClient Customer, ILightningClient Merchant) GetTestedEclairPair()
+			=> ("Eclair", CreateEclairClient(), CreateEclairClientDest());
+
 		public static IEnumerable<(string Name, ILightningClient Customer, ILightningClient Merchant)> GetTestedPairs()
 		{
-			yield return ("C-Lightning", CreateCLightningClient(), CreateCLightningClientDest());
-			yield return ("LND", CreateLndClient(), CreateLndClientDest());
-			yield return ("Eclair", CreateEclairClient(), CreateEclairClientDest());
+			yield return GetTestedCLightningPair();
+			yield return GetTestedLndPair();
+			yield return GetTestedEclairPair();
 		}
 	}
 }