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bpftrace Tests

There are four different types of tests: unit, self, runtime, and tool parsing.

Every contribution should (1) not break the existing tests and (2) introduce new tests if relevant.

Unit tests

Unit tests for individual components (semantic analyser, codegen, etc.) are based on the GoogleTest framework. These tests can be run with the bpftrace_test executable. Tests can be selected with the --gtest_filter flag or the GTEST_FILTER environment variable, see --help for more information. These are located in tests/*.cpp and are executed by <builddir>/tests/bpftrace_test.

Self tests

These are test: probes written to test core functionality, and standard library functionality. They can be found in tests/self and are run by a simple script.

  • Run: sudo <builddir>/tests/self-tests.sh
  • To debug a test, you can run an individual file directly, e.g. <builddir>src/bpftrace --test <builddir>/tests/<testfile>
  • To run only specific self tests, use --probe-filter REGEX to select tests by name, e.g. <builddir>src/bpftrace --test --probe-filter 'map_' <builddir>/tests/<testfile>

Runtime tests

Runtime tests will call the bpftrace executable. These are located in tests/runtime and are managed by a custom framework.

  • Run (non-Nix): sudo <builddir>/tests/runtime-tests.sh
  • Run (Nix): sudo --preserve-env=PATH --preserve-env=PYTHONPATH ./build/tests/runtime-tests.sh
  • Use the TEST_FILTER environment variable (or the --filter arg when running runtime-tests.sh) to only run a subset of the tests. The passed value should be a colon-separated list of positive and negative (starting with -) regex patterns. Only tests which match any of the positive patterns (by default .*) and none of the negative patterns will be executed. For example, sudo <builddir>/tests/runtime-tests.sh --filter="^uprobe.*:-list" will run all tests from the uprobe suite, except for tests for probe listing.
  • There are environment variables to override paths for the bpftrace executables, if necessary. See runtime-tests.sh for details.

Runtime tests are grouped into "suites". A suite is usually a single file. The name of the file is the name of the suite.

Runtime test directives

Each runtime testcase consists of multiple directives.

Required directives: NAME, (RUN or PROG), (one or more [EXPECT, EXPECT_NONE, EXPECT_REGEX, EXPECT_REGEX_NONE] or a single [EXPECT_FILE, EXPECT_JSON]).

  • AFTER: Run the command in a shell after running bpftrace (after the probes are attached). The command will be terminated after the testcase is over.
  • ARCH: Only run testcase on provided architectures. Supports | to logical OR multiple arches.
  • BEFORE: Run the command in a shell before running bpftrace. The command will run while bpftrace is running and be terminated after the test case finishes. Can be used multiple times, commands will run in parallel.
  • CLEANUP: Run the command in a shell after test is over. This holds any cleanup command to free resources after test completes.
  • ENV: Run bpftrace invocation with additional environment variables. Must be in format NAME=VALUE. Supports multiple values separated by spaces.
  • EXPECT: The expected output. Performs a literal match on an entire line of output. Multi-line EXPECT is supported by whitespace aligning subsequent lines to the beginning column of the first (same as PROG).
    • Example of multi-line EXPECT: 
      NAME multi-line
PROG begin { print("hello!"); print("world!") }
EXPECT hello!
       world!
  • EXPECT_FILE: A file containing the expected output, matched as plain text after stripping initial and final empty lines
  • EXPECT_JSON: A json file containing the expected output, matched after converting the output and the file to a dict (thus ignoring field order).
  • EXPECT_NONE: The negation of EXPECT.
  • EXPECT_REGEX: A python regular expression to match the expected output.
  • EXPECT_REGEX_NONE: The negation of EXPECT_REGEX.
  • MAX_KERNEL: Skip the test unless the host's kernel version is <= the provided kernel version. Try not to use this directive as kernel versions may be misleading (backported kernel features, for example).
  • MIN_KERNEL: Skip the test unless the host's kernel version is >= the provided kernel version. Try not to use this directive as kernel versions may be misleading (backported kernel features, for example).
  • NAME: Name of the test case. This field is required.
  • NEW_PIDNS: This will execute the BEFORE, the bpftrace (RUN or PROG), and the AFTER commands in a new pid namespace that mounts proc. At least one BEFORE is required.
  • PROG: Run the provided bpftrace program. This directive is preferred over RUN unless you must pass flags or create a shell pipeline. This XOR the RUN field is required. Multi-line program is supported by whitespace aligning subsequent lines to the beginning column of the first.
    • Example of multi-line program: 
      NAME multi-line
PROG begin { printf("hello ") }
     end { printf("world!\n") }
EXPECT hello world!
  • REQUIRES: Run a command in a shell. If it succeeds, run the testcase. Else, skip the testcase.
  • REQUIRES_FEATURE: Only run testcase if the following bpftrace feature is built in. See bpftrace --info and runtime/engine/runner.py for more details. Also supports negative features (by prefixing ! before feature).
  • RETURN_CODE: Require that bpftrace exit with specified return code.
  • RUN: Run the command in a shell. See "Runtime variables" below for available placeholders. This XOR the PROG field is required
  • SETUP: Run the command in a shell before the test is run. This differs from the BEFORE directive in that setup commands are expected to exit before bpftrace is executed.
  • SKIP_IF_ENV_HAS: Skip test case if specified environment variable is found and matches value provided. Accepted format is KEY=VALUE. Only a single key/value pair per test is accepted.
  • TIMEOUT: The timeout for the testcase (in seconds). This field is required.
  • WILL_FAIL: Mark that this test case will exit uncleanly (ie exit code != 0)
  • LOCALIZE_TIMESTAMPS: Before comparing actual output to expected output, format %H timestamp strings to match the local time zone. This currently only works with EXPECT_FILE.

If you need to run a test program to probe (eg, uprobe/USDT), you can use the BEFORE clause. The test scripts will wait for the test program to have a pid.

The BEFORE clause will block up to the TIMEOUT waiting for a PID matching the basename of the last space-separated token. For instance, if the BEFORE clause is ./testprogs/usdt_test, it will wait for a processed called usdt_test. If it is ./testprogs/mountns_wrapper usdt_test it will also wait for a process called usdt_test. This approach is invalidated if a test program requires arguments in the future, but so far test programs are simple and separate minimal programs to test tracing functionality, and argument passing hasn't been required. If test programs need arguments, a more sophisticated approach will be necessary.

Comments

Lines starting with a # character are treated as comments and are ignored by the test framework. This allows you to add explanatory notes or documentation within your test files without affecting test execution.

Trailing comments are are not supported.

Runtime variables

Runtime variables are placeholders that the runtime test engine will fill out before running the test. These exist b/c the values of the variables are generally not known until test time. The following runtime variables are available for the RUN directive:

  • {{BPFTRACE}}: Path to bpftrace executable
  • {{BEFORE_PID}}: Process ID of the process in the first BEFORE directive

Test programs

You can add test programs for your runtime tests by placing a .c or .cpp file corresponding to your test program in tests/testprogs.

You can add test libraries for your runtime tests by placing a .c or .cpp file corresponding to your test library in tests/testlibs.

The test file tests/testprogs/my_test.c will result in an executable that you can call and probe in your runtime test at ./testprogs/my_test

This is intended to be useful for testing uprobes and USDT probes, or using uprobes to verify some other behavior in bpftrace. It can also be used to tightly control what code paths are triggered in the system.

Tool parsing tests

Tools parsing tests run every tool in the tools/ directory and ensure that the tools shipped with bpftrace are valid and can run. The validity of tools outputs is not checked at the moment.

Tests can be executed by: sudo <builddir>/tests/tools-parsing-test.sh

Flags and variables

The following environment variables can be set to modify the behaviour of the test suite

  • BPFTRACE_EXECUTABLE: location of the bpftrace executable, if left unset the script attempts to autodetect it.
  • TOOLS_TEST_DISABLE: comma separated list of tools to skip, e.g. vfscount.bt,swapin.bt
  • TOOLS_TEST_OLDVERSION: tests the tools/old version of these tools instead.