This test is no longer relevant. It was introduced in 8c222dca4f961ad13ec64d690134a40d09b20813 to check the switch to 1MB blocks after the BDB too-many-locks issue back in 2013. The switching code has been long since removed. It also needs a specific data file that is hard to find. I've verified in #6320 that it still passes, however I think there is zero reason to keep it. Closes #6320.
Notes
The sources in this directory are unit test cases. Boost includes a unit testing framework, and since bitcoin 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 setup to compile an executable called "test_bitcoin" that runs all of the unit tests. The main source file is called test_bitcoin.cpp, which simply includes other files that contain the actual unit tests (outside of a couple required preprocessor directives). 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 examples of this pattern, examine uint160_tests.cpp and uint256_tests.cpp.
Add the source files to /src/Makefile.test.include to add them to the build.
For further reading, I found the following website to be helpful in explaining how the boost unit test framework works: http://www.alittlemadness.com/2009/03/31/c-unit-testing-with-boosttest/.
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
... or to run just the doubledash test:
test_bitcoin --run_test=getarg_tests/doubledash
Run test_bitcoin --help for the full list.