cltester: Block Control

The test_chain class gives you control over block production, including control over time.

start_block

At any point, you can start producing a new block:

chain.start_block();

This finishes producing the current block (if one is being produced), then starts producing a new one. All transactions after this point go into the new block.

You can skip time:

chain.start_block(2000); // skip 2000ms-worth of blocks

0 skips nothing; the new block is 500ms after the current block being produced (if any), or 500ms after the previous block.
500 skips 1 block
1000 skips 2 blocks

You can also skip to a specific time:

chain.start_block("2020-07-03T15:29:59.500");

eosio::time_point t = ...;
chain.start_block(t);

Note when skipping time: start_block creates an empty block immediately before the new one. This allows TAPoS to operate correctly after skipping large periods of time.

finish_block

At any point, you can stop producing the current block:

chain.finish_block();

After you call finish_block, the system is in a state where no blocks are being produced. The following cause the system to start producing a new block:

using start_block
pushing a transaction
using finish_block again. This causes the system to start a new block then finish it.

Getting the head block time

This gets the head block time as a time_point:

auto t = chain.get_head_block_info().timestamp.to_time_point();

Note: the head block is not the block that's currently being produced. Instead, it's the last block which was finished.

You can display the time:

std::cout << convert_to_json(t) << "\n";

You can also do arithmetic on time:

chain.start_block(
   chain.get_head_block_info().timestamp.to_time_point() +
   eosio::days(8) + eosio::hours(1));

Fixing duplicate transactions

It's easy to create a test which tries to push duplicate transactions. Call start_block before the duplicate transaction to solve this.

Fixing full blocks

It's easy to overfill a block, causing a test failure. Use start_block to solve this.

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