BitcoindComparisonTool.jar is a tool that uses the bitcoinj library
to generate very-low-difficulty blockchains that test edge-cases in
block chain logic.

Full implementations of the Bitcoin protocol can use it to help
test that their logic for handling valid/invalid blocks matches
the reference implementation.

Improvements are welcome; the source code used to generate the blocks
is in FullBlockTestGenerator.java. The source that drives the tool can
be found at
https://github.com/TheBlueMatt/bitcoinj/blob/blocktester/core/src/test/java/org/bitcoinj/core/BitcoindComparisonTool.java