bitcoin/src/test/README.md

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, which includes unit tests from subtrees, or make && make -C src check-unit for just the unit tests.

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 accepts the command line arguments from the boost framework. For example, to run just the getarg_tests suite of tests:

test_bitcoin --log_level=all --run_test=getarg_tests

log_level controls the verbosity of the test framework, which logs when a test case is entered, for example.

test_bitcoin also accepts some of the command line arguments accepted by bitcoind. Use -- to separate these sets of arguments:

test_bitcoin --log_level=all --run_test=getarg_tests -- -printtoconsole=1

The -printtoconsole=1 after the two dashes sends debug logging, which normally goes only to debug.log within the data directory, also to the standard terminal output.

... or to run just the doubledash test:

test_bitcoin --run_test=getarg_tests/doubledash

test_bitcoin creates a temporary working (data) directory with a randomly generated pathname within test_common_Bitcoin Core/, which in turn is within the system's temporary directory (see temp_directory_path). This data directory looks like a simplified form of the standard bitcoind data directory. Its content will vary depending on the test, but it will always have a debug.log file, for example.

The location of the temporary data directory can be specified with the -testdatadir option. This can make debugging easier. The directory path used is the argument path appended with /test_common_Bitcoin Core/<test-name>/datadir. The directory path is created if necessary. Specifying this argument also causes the data directory not to be removed after the last test. This is useful for looking at what the test wrote to debug.log after it completes, for example. (The directory is removed at the start of the next test run, so no leftover state is used.)

$ test_bitcoin --run_test=getarg_tests/doubledash -- -testdatadir=/somewhere/mydatadir
Test directory (will not be deleted): "/somewhere/mydatadir/test_common_Bitcoin Core/getarg_tests/doubledash/datadir
Running 1 test case...

*** No errors detected
$ ls -l '/somewhere/mydatadir/test_common_Bitcoin Core/getarg_tests/doubledash/datadir'
total 8
drwxrwxr-x 2 admin admin 4096 Nov 27 22:45 blocks
-rw-rw-r-- 1 admin admin 1003 Nov 27 22:45 debug.log

If you run an entire test suite, such as --run_test=getarg_tests, or all the test suites (by not specifying --run_test), a separate directory will be created for each individual test.

Run test_bitcoin --help for the full list of tests.

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 gdb or 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