`Chain.GetHeaders` steps by `1 + Skip` in the forward branch but by `1 -
Skip` in the reverse branch. `Skip` is a `uint64`, so the reverse stride
is wrong for every `Skip > 0`:
| Skip | reverse step | result |
| --- | --- | --- |
| 0 | `-= 1` | correct |
| 1 | `-= 0` | block number never moves, the same header is returned
`Amount` times |
| >= 2 | `1 - Skip` underflows | walks *forward* instead of back (`Skip
= 2` on block 100 lands on 101) |
Per the `GetBlockHeadersRequest` definition, `Skip` is "Blocks to skip
between consecutive headers", so the stride is `Skip + 1` in whichever
direction the query runs. Subtracting `1 + Skip` makes the reverse
branch mirror the forward one.
The existing table test covers forward + `Skip: 1` and reverse + `Skip:
0` (which works by accident, since `1 - 0 == 1`). Added the missing
reverse + `Skip: 1` case; it fails on master:
```
--- FAIL: TestChainGetHeaders/3
Test: TestChainGetHeaders/3
FAIL github.com/ethereum/go-ethereum/cmd/devp2p/internal/ethtest
```
and passes with the fix (4/4).
No caller sends a reverse request with `Skip > 0` today, so nothing is
broken in the current suite. The helper computes the expected headers
that responses are checked against, though, so the moment a reverse+skip
case is added it would silently assert the wrong headers rather than
fail loudly.
Here we update the eth and snap protocol test suites with a new test chain,
created by the hivechain tool. The new test chain uses proof-of-stake. As such,
tests using PoW block propagation in the eth protocol are removed. The test suite
now connects to the node under test using the engine API in order to make it
accept transactions.
The snap protocol test suite has been rewritten to output test descriptions and
log requests more verbosely.
---------
Co-authored-by: Felix Lange <fjl@twurst.com>
This PR replaces the old test genesis.json and chain.rlp files in the testdata
directory for the eth protocol test suite, and also adds documentation for
running the eth test suite locally.
It also improves the test output text and adds more timeouts.
Co-authored-by: Felix Lange <fjl@twurst.com>
