test: Fix intermittent issues in feature_assumevalid.py #34571

1. 
   maflcko commented at 10:29 AM on February 12, 2026: member

   The test has many issues:

   • The send_blocks_until_disconnected seems to imply to wait until a disconnect happens. However, in reality it will blindly send all blocks and then return early, when done or when a disconnect happens. This will cause test failures when python is running faster than Bitcoin Core, for example when using sanitizers.
   • The assert_debug_log scopes are bloated, which makes finding the above issue harder. This is, because a test failure will basically print the 1000+ line debug log excerpt twice, with the second instance stripped of useful python test logs. Also, the checks are less precise, if they happen over a larger scope/snippet.

   Fix all issues, by:

   • Removing send_blocks_until_disconnected and just sending the blocks that are needed to get the disconnect and then explicitly waiting for the disconnect.
   • Reduce the scopes of the debug log checks. This can be reviewed with the git options --color-moved=dimmed-zebra --color-moved-ws=ignore-all-space.
2. test: Fix intermittent issues in feature_assumevalid.py fa90d44a22
3. DrahtBot added the label Tests on Feb 12, 2026
4. 
   DrahtBot commented at 10:29 AM on February 12, 2026: contributor

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5. 
   maflcko commented at 10:36 AM on February 12, 2026: member

   Locally, I can reproduce the intermittent issue via while ./bld-cmake/test/functional/feature_assumevalid.py --timeout-factor=4 --valgrind ; do echo >> /tmp/runs_fa ; done.

   An alternative could be:

   diff --git a/src/validationinterface.cpp b/src/validationinterface.cpp
   index c7be6abc3a..aacb7b6563 100644
   --- a/src/validationinterface.cpp
   +++ b/src/validationinterface.cpp
   @@ -14,2 +14,3 @@
    #include <primitives/transaction.h>
   +#include <random.h>
    #include <util/check.h>
   @@ -156,2 +157,4 @@ void ValidationSignals::SyncWithValidationInterfaceQueue()
    
   +static FastRandomContext g_rnd{};
   +
    // Use a macro instead of a function for conditional logging to prevent
   @@ -166,2 +169,3 @@ void ValidationSignals::SyncWithValidationInterfaceQueue()
                LOG_EVENT(fmt, local_name, __VA_ARGS__);           \
   +            if(g_rnd.randrange(2)<1)UninterruptibleSleep(15ms);\
                event();                                           \
   

   <!-- [#32975 (review)](/bitcoin-bitcoin/32975/#discussion_r2240783171)

6. fanquake added this to the milestone 31.0 on Feb 12, 2026
7. 
   maflcko commented at 1:24 PM on February 17, 2026: member

   cc @l0rinc as the author of the code, you may be qualified to review this

8. fanquake referenced this in commit 9e4567b17a on Feb 18, 2026
9. 
   l0rinc commented at 5:35 PM on February 18, 2026: contributor

   ACK fa90d44a22838591e47eec206c23f87d69ad842a

   The test has many issues

   As the author of this test with many issues, thanks for the ping and for fixing the racy tests.

   I had to separate the change into smaller commits to understand what was being changed. I pushed it to https://github.com/l0rinc/bitcoin/pull/120/commits in case you decide to take anything from it:

   • send the first 103 blocks explicitly, then wait for disconnect
   • convert inline comments to logs
   • move-only P2P/header/chain setup outside the assert to minimize scope
   • check the first block explicitly, then process the rest
   • replace residual wait_until polling with synchronized sends and direct assert_equal
   • add the missing node2 invalid-chaintip assertion, and simplify the node1 height check to avoid an unnecessary RPC call

   I can confirm this passes with the UninterruptibleSleep hack for cmake -B build -DCMAKE_BUILD_TYPE=Debug && cmake --build build -j && build/test/functional/test_runner.py feature_assumevalid.py, and fails reliably without these fixes.

10. 
    maflcko commented at 8:49 AM on February 19, 2026: member

    Thanks. I think I'll leave it as-is for now, but reviewers are welcome to review your branch instead, if that is easier for them. Afterward, they can confirm there is no diff ($ git diff fa90d44a22838591e47eec206c23f87d69ad842a de739aaa8a3d4ae9218cf808efe9de73c47b6087 -- test/functional/feature_assumevalid.py) and ack the single commit here.

11. 
    achow101 commented at 10:03 PM on February 19, 2026: member

    ACK fa90d44a22838591e47eec206c23f87d69ad842a

12. achow101 merged this on Feb 20, 2026
13. achow101 closed this on Feb 20, 2026

    ---

14. maflcko deleted the branch on Feb 20, 2026

Milestone
31.0