Add a second on writing tests, covering when to use Python and C, where to put the tests, etc. Add a link to the existing Python test documentation.
Signed-off-by: Simon Glass sjg@chromium.org ---
Changes in v4: - Add correct SPDX header
Changes in v2: - Add new patches to cover running an SPL test
doc/develop/index.rst | 1 + doc/develop/py_testing.rst | 3 +- doc/develop/testing.rst | 2 + doc/develop/tests_sandbox.rst | 7 + doc/develop/tests_writing.rst | 339 ++++++++++++++++++++++++++++++++++ 5 files changed, 351 insertions(+), 1 deletion(-) create mode 100644 doc/develop/tests_writing.rst
diff --git a/doc/develop/index.rst b/doc/develop/index.rst index 9208668a2d4..8f0a598b5f2 100644 --- a/doc/develop/index.rst +++ b/doc/develop/index.rst @@ -32,6 +32,7 @@ Testing
testing py_testing + tests_writing tests_sandbox
Refactoring diff --git a/doc/develop/py_testing.rst b/doc/develop/py_testing.rst index 7f01858cfda..c4cecc0a01b 100644 --- a/doc/develop/py_testing.rst +++ b/doc/develop/py_testing.rst @@ -13,7 +13,8 @@ results. Advantages of this approach are: U-Boot; there can be no disconnect. - There is no need to write or embed test-related code into U-Boot itself. It is asserted that writing test-related code in Python is simpler and more - flexible than writing it all in C. + flexible than writing it all in C. But see :doc:`tests_writing` for caveats + and more discussion / analysis. - It is reasonably simple to interact with U-Boot in this way.
Requirements diff --git a/doc/develop/testing.rst b/doc/develop/testing.rst index b181c2e2e41..ced13ac8bb4 100644 --- a/doc/develop/testing.rst +++ b/doc/develop/testing.rst @@ -117,6 +117,8 @@ or is covered sparingly. So here are some suggestions: is much easier to add onto a test - writing a new large test can seem daunting to most contributors.
+See doc:`tests_writing` for how to write tests. +
Future work ----------- diff --git a/doc/develop/tests_sandbox.rst b/doc/develop/tests_sandbox.rst index 8c2eac4c5f4..7e5cc84e43c 100644 --- a/doc/develop/tests_sandbox.rst +++ b/doc/develop/tests_sandbox.rst @@ -199,3 +199,10 @@ linker_list:: 000000000001f240 D _u_boot_list_2_dm_test_2_dm_test_of_plat_parent 000000000001f260 D _u_boot_list_2_dm_test_2_dm_test_of_plat_phandle 000000000001f280 D _u_boot_list_2_dm_test_2_dm_test_of_plat_props + + +Writing tests +------------- + +See :doc:`tests_writing` for how to write new tests. + diff --git a/doc/develop/tests_writing.rst b/doc/develop/tests_writing.rst new file mode 100644 index 00000000000..d926c00f6e1 --- /dev/null +++ b/doc/develop/tests_writing.rst @@ -0,0 +1,339 @@ +.. SPDX-License-Identifier: GPL-2.0+ +.. Copyright 2021 Google LLC +.. sectionauthor:: Simon Glass sjg@chromium.org + +Writing Tests +============= + +This describes how to write tests in U-Boot and describes the possible options. + +Test types +---------- + +There are two basic types of test in U-Boot: + + - Python tests, in test/py/tests + - C tests, in test/ and its subdirectories + +Python tests talk to U-Boot via the command line. They support both sandbox and +real hardware. They typically do not require building test code into U-Boot +itself. They are fairly slow to run, due to the command-line interface and there +being two separate processes. Python tests are fairly easy to write. They can +be a little tricky to debug sometimes due to the voluminous output of pytest. + +C tests are written directly in U-Boot. While they can be used on boards, they +are more commonly used with sandbox, as they obviously add to U-Boot code size. +C tests are easy to write so long as the required facilities exist. Where they +do not it can involve refactoring or adding new features to sandbox. They are +fast to run and easy to debug. + +Regardless of which test type is used, all tests are collected and run by the +pytest framework, so there is typically no need to run them separately. This +means that C tests can be used when it makes sense, and Python tests when it +doesn't. + + +This table shows how to decide whether to write a C or Python test: + +===================== =========================== ============================= +Attribute C test Python test +===================== =========================== ============================= +Fast to run? Yes No (two separate processes) +Easy to write? Yes, if required test Yes + features exist in sandbox +Needs code in U-Boot? Yes No, provided the test can be + executed and the result + determined using the command + line +Easy to debug? Yes Yes, but the amount of output can + sometimes require a bit of digging +Can use gdb? Yes, directly Yes, with --gdbserver +Can run on boards? Some can, but only if Yes + compiled in and not + dependent on sandboxau +===================== =========================== ============================= + + +Python or C +----------- + +Typically in U-Boot we encourage C test using sandbox for all features. This +allows fast testing, easy development and allows contributors to make changes +without needing dozens of boards to test with. + +When a test requires setup or interaction with the running host (such as to +generate images and then running U-Boot to check that they can be loaded), or +cannot be run on sandbox, Python tests should be used. These should typically +NOT rely on running with sandbox, but instead should function correctly on any +board supported by U-Boot. + + +How slow are Python tests? +-------------------------- + +Under the hood, Python tests work by starting a sandbox test and connecting to +it via a pipe. Each interaction with the U-Boot process requires at least a +context switch to handle the pipe interaction. The test sends a command to +U-Boot, which then reacts and shows some output, then the test sees that and +continues. Of course on real hardware, communications delays (e.g. with a serial +console) make this slower. + +For comparison, consider a test that checks the 'md' (memory dump). All times +below are approximate, as measured on an AMD 2950X system. Here is is the test +in Python:: + + @pytest.mark.buildconfigspec('cmd_memory') + def test_md(u_boot_console): + """Test that md reads memory as expected, and that memory can be modified + using the mw command.""" + + ram_base = u_boot_utils.find_ram_base(u_boot_console) + addr = '%08x' % ram_base + val = 'a5f09876' + expected_response = addr + ': ' + val + u_boot_console.run_command('mw ' + addr + ' 0 10') + response = u_boot_console.run_command('md ' + addr + ' 10') + assert(not (expected_response in response)) + u_boot_console.run_command('mw ' + addr + ' ' + val) + response = u_boot_console.run_command('md ' + addr + ' 10') + assert(expected_response in response) + +This runs a few commands and checks the output. Note that it runs a command, +waits for the response and then checks it agains what is expected. If run by +itself it takes around 800ms, including test collection. For 1000 runs it takes +19 seconds, or 19ms per run. Of course 1000 runs it not that useful since we +only want to run it once. + +There is no exactly equivalent C test, but here is a similar one that tests 'ms' +(memory search):: + + /* Test 'ms' command with bytes */ + static int mem_test_ms_b(struct unit_test_state *uts) + { + u8 *buf; + + buf = map_sysmem(0, BUF_SIZE + 1); + memset(buf, '\0', BUF_SIZE); + buf[0x0] = 0x12; + buf[0x31] = 0x12; + buf[0xff] = 0x12; + buf[0x100] = 0x12; + ut_assertok(console_record_reset_enable()); + run_command("ms.b 1 ff 12", 0); + ut_assert_nextline("00000030: 00 12 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................"); + ut_assert_nextline("--"); + ut_assert_nextline("000000f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 12 ................"); + ut_assert_nextline("2 matches"); + ut_assert_console_end(); + + ut_asserteq(2, env_get_hex("memmatches", 0)); + ut_asserteq(0xff, env_get_hex("memaddr", 0)); + ut_asserteq(0xfe, env_get_hex("mempos", 0)); + + unmap_sysmem(buf); + + return 0; + } + MEM_TEST(mem_test_ms_b, UT_TESTF_CONSOLE_REC); + +This runs the command directly in U-Boot, then checks the console output, also +directly in U-Boot. If run by itself this takes 100ms. For 1000 runs it takes +660ms, or 0.66ms per run. + +So overall running a C test is perhaps 8 times faster individually and the +interactions are perhaps 25 times faster. + +It should also be noted that the C test is fairly easy to debug. You can set a +breakpoint on do_mem_search(), which is what implements the 'ms' command, +single step to see what might be wrong, etc. That is also possible with the +pytest, but requires two terminals and --gdbserver. + + +Why does speed matter? +---------------------- + +Many development activities rely on running tests: + + - 'git bisect run make qcheck' can be used to find a failing commit + - test-driven development relies on quick iteration of build/test + - U-Boot's continuous integration (CI) systems make use of tests. Running + all sandbox tests typically takes 90 seconds and running each qemu test + takes about 30 seconds. This is currently dwarfed by the time taken to + build all boards + +As U-Boot continues to grow its feature set, fast and reliable tests are a +critical factor factor in developer productivity and happiness. + + +Writing C tests +--------------- + +C tests are arranged into suites which are typically executed by the 'ut' +command. Each suite is in its own file. This section describes how to accomplish +some common test tasks. + + +Add a new driver model test +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Use this when adding a test for a new or existing uclass, adding new operations +or features to a uclass, adding new ofnode or dev_read_() functions, or anything +else related to driver model. + +Find a suitable place for your test, perhaps near other test functions in +existing code, or in a new file. Each uclass should have its own test file. + +Declare the test with:: + + /* Test that ... */ + static int dm_test_uclassname_what(struct unit_test_state *uts) + { + /* test code here */ + + return 0; + } + DM_TEST(dm_test_uclassname_what, UT_TESTF_SCAN_FDT); + +Replace 'uclassname' with the name of your uclass, if applicable. Replace 'what' +with what you are testing. + +The flags for DM_TEST() are defined in test/test.h and you typically want +UT_TESTF_SCAN_FDT so that the devicetree is scanned and all devices are bound +and ready for use. The DM_TEST macro adds UT_TESTF_DM automatically so that +the test runner knows it is a driver model test. + +Driver model tests are special in that the entire driver model state is +recreated anew for each test. This ensures that if a previous test deletes a +device, for example, it does not affect subsequent tests. Driver model tests +also run both with livetree and flattree, to ensure that both devicetree +implementations work as expected. + +Example commit: c48cb7ebfb4 ("sandbox: add ADC unit tests") [1] + +[1] https://gitlab.denx.de/u-boot/u-boot/-/commit/c48cb7ebfb4 + + +Add a C test to an existing suite +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Use this when you are adding to or modifying an existing feature outside driver +model. An example is bloblist. + +Add a new function in the same file as the rest of the suite and register it +with the suite. For example, to add a new mem_search test:: + + /* Test 'ms' command with 32-bit values */ + static int mem_test_ms_new_thing(struct unit_test_state *uts) + { + /* test code here*/ + + return 0; + } + MEM_TEST(mem_test_ms_new_thing, UT_TESTF_CONSOLE_REC); + +Note that the MEM_TEST() macros is defined at the top of the file. + +Example commit: 9fe064646d2 ("bloblist: Support relocating to a larger space") [1] + +[1] https://gitlab.denx.de/u-boot/u-boot/-/commit/9fe064646d2 + + +Add a new test suite +~~~~~~~~~~~~~~~~~~~~ + +Each suite should focus on one feature or subsystem, so if you are writing a +new one of those, you should add a new suite. + +Create a new file in test/ or a subdirectory and define a macro to register the +suite. For example:: + + #include <common.h> + #include <console.h> + #include <mapmem.h> + #include <dm/test.h> + #include <test/ut.h> + + /* Declare a new wibble test */ + #define WIBBLE_TEST(_name, _flags) UNIT_TEST(_name, _flags, wibble_test) + + /* Tetss go here */ + + /* At the bottom of the file: */ + + int do_ut_wibble(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[]) + { + struct unit_test *tests = UNIT_TEST_SUITE_START(wibble_test); + const int n_ents = UNIT_TEST_SUITE_COUNT(wibble_test); + + return cmd_ut_category("cmd_wibble", "wibble_test_", tests, n_ents, argc, argv); + } + +Then add new tests to it as above. + +Register this new suite in test/cmd_ut.c by adding to cmd_ut_sub[]:: + + /* Within cmd_ut_sub[]... */ + + U_BOOT_CMD_MKENT(wibble, CONFIG_SYS_MAXARGS, 1, do_ut_wibble, "", ""), + +and adding new help to ut_help_text[]:: + + "ut wibble - Test the wibble feature\n" + +If your feature is conditional on a particular Kconfig, then you can use #ifdef +to control that. + +Finally, add the test to the build by adding to the Makefile in the same +directory:: + + obj-$(CONFIG_$(SPL_)CMDLINE) += wibble.o + +Note that CMDLINE is never enabled in SPL, so this test will only be present in +U-Boot proper. See below for how to do SPL tests. + +As before, you can add an extra Kconfig check if needed:: + + ifneq ($(CONFIG_$(SPL_)WIBBLE),) + obj-$(CONFIG_$(SPL_)CMDLINE) += wibble.o + endif + + +Example commit: 919e7a8fb64 ("test: Add a simple test for bloblist") [1] + +[1] https://gitlab.denx.de/u-boot/u-boot/-/commit/919e7a8fb64 + + +Making the test run from pytest +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +All C tests must run from pytest. Typically this is automatic, since pytest +scans the U-Boot executable for available tests to run. So long as you have a +'ut' subcommand for your test suite, it will run. The same applies for driver +model tests since they use the 'ut dm' subcommand. + +See test/py/tests/test_ut.py for how unit tests are run. + + +Add a C test for SPL +~~~~~~~~~~~~~~~~~~~~ + +Note: C tests are only available for sandbox_spl at present. There is currently +no mechanism in other boards to existing SPL tests even if they are built into +the image. + +SPL tests cannot be run from the 'ut' command since there are no commands +available in SPL. Instead, sandbox (only) calls ut_run_list() on start-up, when +the -u flag is given. This runs the available unit tests, no matter what suite +they are in. + +To create a new SPL test, follow the same rules as above, either adding to an +existing suite or creating a new one. + +An example SPL test is spl_test_load(). + + +Writing Python tests +-------------------- + +See :doc:`py_testing` for brief notes how to write Python tests. You +should be able to use the existing tests in test/py/tests as examples.