A patch for geth that will cause it to mine every second. This is useful for accelerating unit test of solidity contracts. I will attempt to keep this patch up to date, no guarantees.

geth.patch

    diff --git a/eth/fetcher/fetcher.go b/eth/fetcher/fetcher.go
    index d88d919..f03fd30 100644
    --- a/eth/fetcher/fetcher.go
    +++ b/eth/fetcher/fetcher.go
    @@ -34,7 +34,7 @@ import (
     const (
        arriveTimeout = 500 * time.Millisecond // Time allowance before an announced block is explicitlrd
        gatherSlack   = 100 * time.Millisecond // Interval used to collate almost-expired announces witfs
    -   fetchTimeout  = 5 * time.Second        // Maximum alloted time to return an explicitly requestebk
    +   fetchTimeout  = 1 * time.Second        // Maximum alloted time to return an explicitly requestebk
        maxUncleDist  = 7                      // Maximum allowed backward distance from the chain head
        maxQueueDist  = 32                     // Maximum allowed distance from the chain head to queue
        hashLimit     = 256                    // Maximum number of unique blocks a peer may have annoued
    diff --git a/eth/peer.go b/eth/peer.go
    index 15ba22f..0201057 100644
    --- a/eth/peer.go
    +++ b/eth/peer.go
    @@ -41,7 +41,7 @@ var (
     const (
        maxKnownTxs      = 32768 // Maximum transactions hashes to keep in the known list (prevent DOS)
        maxKnownBlocks   = 1024  // Maximum block hashes to keep in the known list (prevent DOS)
    -   handshakeTimeout = 5 * time.Second
    +   handshakeTimeout = 1 * time.Second
     )
     
     // PeerInfo represents a short summary of the Ethereum sub-protocol metadata known
    diff --git a/miner/worker.go b/miner/worker.go
    index 754a6fc..2b62b59 100644
    --- a/miner/worker.go
    +++ b/miner/worker.go
    @@ -466,7 +466,7 @@ func (self *worker) commitNewWork() {
                tstamp = parent.Time().Int64() + 1
        }
        // this will ensure we're not going off too far in the future
    -   if now := time.Now().Unix(); tstamp > now+4 {
    +   if now := time.Now().Unix(); tstamp > now {
                wait := time.Duration(tstamp-now) * time.Second
                glog.V(logger.Info).Infoln("We are too far in the future. Waiting for", wait)
                time.Sleep(wait)
    diff --git a/p2p/rlpx.go b/p2p/rlpx.go
    index aaa7338..ce82eb7 100644
    --- a/p2p/rlpx.go
    +++ b/p2p/rlpx.go
    @@ -57,7 +57,7 @@ const (
     
        // total timeout for encryption handshake and protocol
        // handshake in both directions.
    -   handshakeTimeout = 5 * time.Second
    +   handshakeTimeout = 2 * time.Second
     
        // This is the timeout for sending the disconnect reason.
        // This is shorter than the usual timeout because we don't want
    diff --git a/params/protocol_params.go b/params/protocol_params.go
    index dcc17e0..21a49c5 100755
    --- a/params/protocol_params.go
    +++ b/params/protocol_params.go
    @@ -29,10 +29,10 @@ var (
        CallNewAccountGas      = big.NewInt(25000)  // Paid for CALL when the destination address didn'e.
        TxGas                  = big.NewInt(21000)  // Per transaction. NOTE: Not payable on data of cas.
        TxDataZeroGas          = big.NewInt(4)      // Per byte of data attached to a transaction that u.
    -   DifficultyBoundDivisor = big.NewInt(2048)   // The bound divisor of the difficulty, used in thep.
    +   DifficultyBoundDivisor = big.NewInt(1)      // The bound divisor of the difficulty, used in thep.
        QuadCoeffDiv           = big.NewInt(512)    // Divisor for the quadratic particle of the memoryo.
    -   GenesisDifficulty      = big.NewInt(131072) // Difficulty of the Genesis block.
    -   DurationLimit          = big.NewInt(13)     // The decision boundary on the blocktime duration e.
    +   GenesisDifficulty      = big.NewInt(1)      // Difficulty of the Genesis block.
    +   DurationLimit          = big.NewInt(1)      // The decision boundary on the blocktime duration e.
        SstoreSetGas           = big.NewInt(20000)  // Once per SLOAD operation.
        LogDataGas             = big.NewInt(8)      // Per byte in a LOG* operation's data.
        CallStipend            = big.NewInt(2300)   // Free gas given at beginning of call.
    @@ -57,7 +57,7 @@ var (
        CreateDataGas        = big.NewInt(200)    //
        Ripemd160Gas         = big.NewInt(600)    //
        Ripemd160WordGas     = big.NewInt(120)    //
    -   MinimumDifficulty    = big.NewInt(131072) // The minimum that the difficulty may ever be.
    +   MinimumDifficulty    = big.NewInt(1)      // The minimum that the difficulty may ever be.
        CallCreateDepth      = big.NewInt(1024)   // Maximum depth of call/create stack.
        ExpGas               = big.NewInt(10)     // Once per EXP instuction.
        LogGas               = big.NewInt(375)    // Per LOG* operation.

Note, I haven't actually run this on a private network, I've only run this as a single node. My goal is to adjust the timeouts such that on a dedicated LAN it should run as fast as possible. I suspect the 1 second timeouts might have to move to 2 seconds. We'll see.