Fix and unify logic for checking mining fee

 - previous logic failed to detect incorrect fee if the capacity was higher than expected

eclair-core/src/test/scala/fr/acinq/eclair/channel/states/e/NormalSplicesStateSpec.scala

@@ -176,14 +176,9 @@ class NormalSplicesStateSpec extends TestKitBaseClass with FixtureAnyFunSuiteLik
 
  initiateSplice(f, spliceOut_opt = Some(SpliceOut(100_000 sat, defaultSpliceOutScriptPubKey)))
 
- val fundingTx1 = alice.stateData.asInstanceOf[DATA_NORMAL].commitments.latest.localFundingStatus.signedTx_opt.get
- val feerate = alice.nodeParams.onChainFeeConf.getFundingFeerate(alice.nodeParams.currentFeerates)
- val expectedMiningFee = Transactions.weight2fee(feerate, fundingTx1.weight())
- val actualMiningFee = 1_400_000.sat - alice.stateData.asInstanceOf[DATA_NORMAL].commitments.latest.capacity
- // fee computation is approximate
- assert(actualMiningFee - expectedMiningFee < 100.sat || expectedMiningFee - actualMiningFee < 100.sat)
  // initiator pays the fee
- assert(alice.stateData.asInstanceOf[DATA_NORMAL].commitments.latest.localCommit.spec.toLocal == 700_000_000.msat - actualMiningFee)
+ val fee = spliceOutFee(f, capacity = 1_400_000.sat)
+ assert(alice.stateData.asInstanceOf[DATA_NORMAL].commitments.latest.localCommit.spec.toLocal == 700_000_000.msat - fee)
  assert(alice.stateData.asInstanceOf[DATA_NORMAL].commitments.latest.localCommit.spec.toRemote == 700_000_000.msat)
  }
 
@@ -1521,13 +1516,13 @@ class NormalSplicesStateSpec extends TestKitBaseClass with FixtureAnyFunSuiteLik
  Seq((preimage1a, htlc1a), (preimage2a, htlc2a), (preimage1b, htlc1b), (preimage2b, htlc2b))
  }
 
- def spliceOutFee(f: FixtureParam): Satoshi = {
+ def spliceOutFee(f: FixtureParam, capacity: Satoshi): Satoshi = {
  import f._
 
- val fundingTx2 = alice.stateData.asInstanceOf[ChannelDataWithCommitments].commitments.latest.localFundingStatus.signedTx_opt.get
+ val fundingTx = alice.stateData.asInstanceOf[ChannelDataWithCommitments].commitments.latest.localFundingStatus.signedTx_opt.get
  val feerate = alice.nodeParams.onChainFeeConf.getFundingFeerate(alice.nodeParams.currentFeerates)
- val expectedMiningFee = Transactions.weight2fee(feerate, fundingTx2.weight())
- val actualMiningFee = 1_900_000.sat - alice.stateData.asInstanceOf[ChannelDataWithCommitments].commitments.latest.capacity
+ val expectedMiningFee = Transactions.weight2fee(feerate, fundingTx.weight())
+ val actualMiningFee = capacity - alice.stateData.asInstanceOf[ChannelDataWithCommitments].commitments.latest.capacity
  // fee computation is approximate
  assert(actualMiningFee >= 0.sat && abs(actualMiningFee - expectedMiningFee) < 100.sat)
  actualMiningFee
@@ -1548,7 +1543,7 @@ class NormalSplicesStateSpec extends TestKitBaseClass with FixtureAnyFunSuiteLik
  def resolveHtlcs(f: FixtureParam, htlcs: Seq[(ByteVector32, UpdateAddHtlc)], paySpliceOutFee: Boolean): Assertion = {
  import f._
 
- val fee = if (paySpliceOutFee) spliceOutFee(f) else 0 sat
+ val fee = if (paySpliceOutFee) spliceOutFee(f, capacity = 1_900_000.sat) else 0 sat
  val Seq((preimage1a, htlc1a), (preimage2a, htlc2a), (preimage1b, htlc1b), (preimage2b, htlc2b)) = htlcs
 
  checkPostSpliceState(f, fee)
@@ -1742,7 +1737,7 @@ class NormalSplicesStateSpec extends TestKitBaseClass with FixtureAnyFunSuiteLik
  // claim-main-delayed tx confirms
  watchConfirmedClaimMainDelayed2.replyTo ! WatchTxConfirmedTriggered(BlockHeight(400000), 42, claimMainDelayed2)
 
- checkPostSpliceState(f, spliceOutFee(f))
+ checkPostSpliceState(f, spliceOutFee(f, capacity = 1_900_000.sat))
 
  // done
  awaitCond(alice.stateName == CLOSED)