24abd8312e
80dc829be7f8c3914074b85bb4c125baba18cb2c tests: Calculate fees more similarly to CFeeRate::GetFee (Andrew Chow)
ce2cc44afd51f3df4ee7f14ea05b8da229183923 tests: Test for assertion when feerate is rounded down (Andrew Chow)
0fbaef9676a1dcb84bcf95afd8d994831ab327b6 fees: Always round up fee calculated from a feerate (Andrew Chow)
Pull request description:
When calculating the fee for a feerate, it is possible that the final calculation will have fractional satoshis. Currently those are ignored via truncation which results in the absolute fee being rounded down. Rounding down is problematic because it results in a feerate that is slightly lower than the feerate represented by the `CFeeRate` object. A slightly lower feerate particularly causes issues for coin selection as it can trigger an assertion error. To avoid potentially underpaying the feerate (and the assertion), always round up the calculated fee.
A test is added for the assertion, along with a comment explaining what happens.
It is unlikely that a user can trigger this as it requires a very specific set of rounding errors to occur as well as the transaction not needing any change and being right on the lower bound of the exact match window. However I was able to trigger the assertion while running coin selection simulations, albeit after thousands of transactions and with some weird feerates.
ACKs for top commit:
ryanofsky:
Code review ACK 80dc829be7f8c3914074b85bb4c125baba18cb2c
promag:
Tested ACK 80dc829be7f8c3914074b85bb4c125baba18cb2c.
lsilva01:
tACK 80dc829
meshcollider:
utACK 80dc829be7f8c3914074b85bb4c125baba18cb2c
Tree-SHA512: fe26684c60f236cab48ea6a4600c141ce766dbe59504ec77595dcbd7fd0b34559acc617007f4f499c9155d8fda0a336954413410ba862b19c765c0cfac79d642
Unit tests
The sources in this directory are unit test cases. Boost includes a unit testing framework, and since Bitcoin Core already uses Boost, it makes sense to simply use this framework rather than require developers to configure some other framework (we want as few impediments to creating unit tests as possible).
The build system is set up to compile an executable called test_bitcoin
that runs all of the unit tests. The main source file for the test library is found in
util/setup_common.cpp.
Compiling/running unit tests
Unit tests will be automatically compiled if dependencies were met in ./configure
and tests weren't explicitly disabled.
After configuring, they can be run with make check.
To run the unit tests manually, launch src/test/test_bitcoin. To recompile
after a test file was modified, run make and then run the test again. If you
modify a non-test file, use make -C src/test to recompile only what's needed
to run the unit tests.
To add more unit tests, add BOOST_AUTO_TEST_CASE functions to the existing
.cpp files in the test/ directory or add new .cpp files that
implement new BOOST_AUTO_TEST_SUITE sections.
To run the GUI unit tests manually, launch src/qt/test/test_bitcoin-qt
To add more GUI unit tests, add them to the src/qt/test/ directory and
the src/qt/test/test_main.cpp file.
Running individual tests
test_bitcoin has some built-in command-line arguments; for
example, to run just the getarg_tests verbosely:
test_bitcoin --log_level=all --run_test=getarg_tests -- DEBUG_LOG_OUT
log_level controls the verbosity of the test framework, which logs when a
test case is entered, for example. The DEBUG_LOG_OUT after the two dashes
redirects the debug log, which would normally go to a file in the test datadir
(BasicTestingSetup::m_path_root), to the standard terminal output.
... or to run just the doubledash test:
test_bitcoin --run_test=getarg_tests/doubledash
Run test_bitcoin --help for the full list.
Adding test cases
To add a new unit test file to our test suite you need
to add the file to src/Makefile.test.include. The pattern is to create
one test file for each class or source file for which you want to create
unit tests. The file naming convention is <source_filename>_tests.cpp
and such files should wrap their tests in a test suite
called <source_filename>_tests. For an example of this pattern,
see uint256_tests.cpp.
Logging and debugging in unit tests
make check will write to a log file foo_tests.cpp.log and display this file
on failure. For running individual tests verbosely, refer to the section
above.
To write to logs from unit tests you need to use specific message methods
provided by Boost. The simplest is BOOST_TEST_MESSAGE.
For debugging you can launch the test_bitcoin executable with gdbor lldb and
start debugging, just like you would with any other program:
gdb src/test/test_bitcoin
Segmentation faults
If you hit a segmentation fault during a test run, you can diagnose where the fault
is happening by running gdb ./src/test/test_bitcoin and then using the bt command
within gdb.
Another tool that can be used to resolve segmentation faults is valgrind.
If for whatever reason you want to produce a core dump file for this fault, you can do
that as well. By default, the boost test runner will intercept system errors and not
produce a core file. To bypass this, add --catch_system_errors=no to the
test_bitcoin arguments and ensure that your ulimits are set properly (e.g. ulimit -c unlimited).
Running the tests and hitting a segmentation fault should now produce a file called core
(on Linux platforms, the file name will likely depend on the contents of
/proc/sys/kernel/core_pattern).
You can then explore the core dump using
gdb src/test/test_bitcoin core
(gbd) bt # produce a backtrace for where a segfault occurred