NetBSD Wiki/tutorials/ Creating atf-based tests for NetBSD src

Contents

  1. Introduction
  2. Test programs vs. test cases
  3. Test case parts
  4. Running the test programs
  5. Adding a new test
  6. C test programs
  7. Shell test programs
  8. FAQ

Introduction

This quick tutorial provides a guideline on how to start creating new test programs and/or test cases, how these tests are tied to the NetBSD source tree and includes a short reference of the most commonly used functions.

You should start by reading the tests(7) manual page, which provides a user-level overview on how to run the tests included in NetBSD. While reading this tutorial, you may also want to refer to these pages on a need-to-know basis: atf-run(1), atf-report(1), atf-test-program(1), atf-c-api(3), atf-sh-api(3) and atf-check(1).

IMPORTANT: Do not take anything for granted, ESPECIALLY if you have previously worked with and/or have seen src/regress/. Your assumptions are most likely incorrect.

Test programs vs. test cases

So, what is what and how do you organize your tests?

A test case is a piece of code that exercises a particular functionality of another piece of code. Commonly, test cases validate the outcome of a particular source function or class method, the validity of the execution of a command with a particular combination of flags/arguments, etc. Test cases are supposed to be very concise, in the sense that they should just be testing one behavior.

A test program is a binary that collects and exposes a group of test cases. Typically, these test programs expose conceptually-related tests or all the tests for a particular source file.

In general, having many test programs with just one test case in them is wrong and smells from the previous layout of src/regress/. Think about some other organization. And don't blame atf for this separation: this is extremely common in (almost?) all other test frameworks and, when used wisely, becomes an invaluable classification.

For example, suppose you have the following fictitious source files for the ls tool:

Then, you could define the following test programs and test cases:

Try to keep your test case names as descriptive as possible so that they do not require comments to explain what they intend to test.

Test case parts

The head

The head is used for the sole purpose to define meta-data properties for the test case. (Eventually, this would not be specified programmatically, but is how we deal with the information right now.)

The following properties are commonly useful:

The body

The body is the actual meat of the test case. This is just a regular function that executes any code you want and calls special atf functions to report failures; see below.

In particular, be aware that the atf run-time isolates the execution of every test case to prevent side-effects (such as temporary file leftovers, in-memory data corruption, etc.). In particular:

Running the test programs

Do:

$ cd /usr/tests/
$ atf-run | atf-report

Why?

Test programs get installed into the /usr/tests/ hierarchy. The main reason for doing that is to allow any user to test his system and to be able to convince himself that everything is working correctly.

Imagine that you install NetBSD-current on a public-facing machine that has some particular hardware only supported in the bleeding-edge source tree. In this scenario, you, as the administrator, could just go into /usr/tests/, run the tests and know immediately if everything is working correctly in your software+hardware combination or not. No need to rely on promises from the vendor, no need to deal with a source tree, no need to have a compiler installed...

So, that's the theory. Now, how does this map to our source tree?

At the moment, the source test programs are located somewhere under src/tests/. Say, for example, that you have the src/tests/bin/ls/ui_test.c source file. This Makefile in src/tests/bin/ls/ will take this source file and generate a ui_test binary. The Makefile will also generate an Atffile. Both files (the ui_test binary and the Atffile) will later be installed to /usr/tests/bin/ls/

Executing a single test

In general, you do not want to run a test program by hand. If you do so, you do not take advantage of any of the isolation provided by the atf runtime. This means that the test program will probably leave some temporary files behind or will raise some false negatives.

To run a test, use atf-run. In general:

$ atf-run | atf-report  # To run all the test programs in a directory.
$ atf-run some_test | atf-report  # To run only the some_test program.

The only "legitimate" case in which you should be running test cases by hand is to debug them:

$ gdb --args ./some_test the_broken_test_case

... but be sure to clean up any leftover files if you do that.

Executing tests during development

When you are in a subdirectory of src/tests/, you can generally run "make test" to execute the tests of that particular subdirectory. This assumes that the tests have been installed into the destdir.

Please note that this is only provided for convenience but it is completely unsupported. Tests run this way may fail mysteriously, and that is perfectly fine as long as they work from their canonical locations in /usr/tests.

Adding a new test

To add a new test case to the source tree, look for any test program in src/tests/ that can assimilate it. If you find such a program, just add the test case to it: no other changes are required so your life is easy. Otherwise, you will have to create a new test program.

To add a new test program to the source tree:

  1. Locate the appropriate subdirectory in which to put your test program. It is OK (and expected) to have multiple test programs into the same directory. Restrain yourself from creating one directory per test program.

If the subdirectory exists:

  1. Choose a sane name for the test program; the name must not be so specific that it restricts the addition of future test cases into it.

  2. Create the test program source file using one of the templates below. E.g. src/tests/tutorial/sample_test.c.

  3. Add the new test program to the Makefile.

If the subdirectory does not exist:

  1. Do the same as above.

  2. Create the Makefile for the directory using the templates below.

  3. Edit the parent Makefile to recurse into the new subdirectory.

  4. Edit src/etc/mtree/NetBSD.dist.tests to register the new subdirectory. Your test will be installed under /usr/tests/.

  5. Edit src/distrib/sets/lists/tests/mi to register the new test program. Do not forget to add .debug entries if your test program is a C/C++ binary.

Makefile template

Follow this template to create your Makefile:

.include <bsd.own.mk>

# This must always be defined.
TESTSDIR= ${TESTSBASE}/bin/ls

# These correspond to the test programs you have in the directory.
TESTS_C+= c1_test c2_test  # Correspond to c1_test.c and c2_test.c.
TESTS_SH+= sh1_test sh2_test  # Correspond to sh1_test.c and sh2_test.c

# Define only if your tests need any data files.
FILESDIR= ${TESTSDIR}
FILES= testdata1.txt testdata2.bin  # Any necessary data files.

.include <bsd.test.mk>

Atffile template

Atffiles are automatically generated by bsd.test.mk, so in general you will not have to deal with them.

What is an Atffile? An Atffile is the atf-run counterpart of a "Makefile". Given that atf tests do not rely on a toolchain, they cannot use make(1) to script their execution as the old tests in src/regress/ did.

The Atffiles, in general, just provide a list of test programs in a particular directory and the list of the subdirectories to descend into.

If you have to provide an Atffile explicitly because the automatic generation does not suit your needs, follow this format:

Content-Type: application/X-atf-atffile; version="1"

prop: test-suite = NetBSD

tp: first_test
tp: second_test
tp-glob: optional_*_test
tp: subdir1
tp: subdir2

C test programs

Template

The following code snippet provides a C test program with two test cases. The specific details as to how this works follow later:

#include <atf-c.h>

ATF_TC(tc, my_test_case);
ATF_TC_HEAD(tc, my_test_case)
{
    atf_tc_set_md_var(tc, "descr", "This test case ensures that...");
}
ATF_TC_BODY(tc, my_test_case)
{
    ATF_CHECK(true); /* Success; continue execution. */
    ATF_CHECK(false); /* Failure; continue execution. */

    ATF_CHECK_EQ(5, 2 + 2); /* Failure; continue execution. */
    ATF_REQUIRE_EQ(5, 2 + 2); /* Failure; abort execution. */

    if (!condition)
        atf_tc_fail("Condition not met!"); /* Abort execution. */
}

ATF_TC(tc, another_test_case);
ATF_TC_HEAD(tc, another_test_case)
{
    atf_tc_set_md_var(tc, "descr", "This test case ensures that...");
}
ATF_TC_BODY(tc, another_test_case)
{
    /* Do more tests here... */
}

ATF_TP_ADD_TCS(tp)
{
    ATF_TP_ADD_TC(tp, my_test_case);
    ATF_TP_ADD_TC(tp, another_test_case);
}

This program needs to be built with the Makefile shown below. Once built, the program automatically gains a main() method that provides a consistent user interface to all test programs. You are simply not intended to provide your own main method, nor to deal with the command-line of the invocation.

How to build

To build a C test program, append the name of the test program (without the .c extension) to the TESTS_C variable in the Makefile.

For example:

.include <bsd.own.mk>

TESTSDIR= ${TESTSBASE}/bin/ls

TESTS_C+= fs_test ui_test

.include <bsd.test.mk>

Common functions

The following functions are commonly used from within a test case body:

Shell test programs

Template

The following code snippet provides a shell test program with two test cases. The details on how this works are provided later:

atf_test_case my_test_case
my_test_case_head() {
    atf_set "descr" "This test case ensures that..."
}
my_test_case_body() {
    touch file1 file2

    cat >expout <<EOF
file1
file2
EOF
    # The following call validates that the 'ls' command returns an
    # exit code of 0, that its stdout matches exactly the contents
    # previously stored in the 'expout' file and that its stderr is
    # completely empty.  See atf-check(1) for details, which is the
    # auxiliary tool invoked by the atf_check wrapper function.
    atf_check -s eq:0 -o file:expout -e empty 'ls'

    atf_check_equal 4 $((2 + 2))

    if [ 'a' != 'b' ]; then
        atf_fail "Condition not met!"  # Explicit failure.
    fi
}

atf_test_case another_test_case
another_test_case_head() {
    atf_set "descr" "This test case ensures that..."
}
another_test_case_body() {
    # Do more tests...
}

atf_init_test_cases() {
    atf_add_test_case my_test_case
    atf_add_test_case another_test_case
}

This program needs to be built with the Makefile shown below. The program automatically gains an entry point that provides a consistent user interface to all test programs. You are simply not intended to provide your own "main method", nor to deal with the command-line of the invocation.

How to build

To build a shell test program, append the name of the test program (without the .sh extension) to the TESTS_SH variable in the Makefile.

For example:

.include <bsd.own.mk>

TESTSDIR= ${TESTSBASE}/bin/ls

TESTS_SH+= integration_test something_else_test

.include <bsd.test.mk>

If you want to run the test program yourself, you should know that shell-based test programs are processed with the atf-sh interpreter. atf-sh is just a thin wrapper over /bin/sh that loads the shared atf code and then delegates execution to your source file.

Common functions

The following functions are commonly used from within a test case body:

FAQ

How do I atfify a plain test program?

Let's suppose you have a program to exercise a particular piece of code. Conceptually this implements a test but it does not use atf at all. For example:

#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* This test program exercises the snprintf function. */

int main(void)
{
    char buf[1024];

    printf("Testing integers");
    snprintf(buf, sizeof(buf), "%d", 3);
    if (strcmp(buf, "3") != 0)
        errx(EXIT_FAILURE, "%d failed");
    snprintf(buf, sizeof(buf), "a %d b", 5);
    if (strcmp(buf, "a 5 b") != 0)
        errx(EXIT_FAILURE, "%d failed");

    printf("Testing strings");
    snprintf(buf, sizeof(buf), "%s", "foo");
    if (strcmp(buf, "foo") != 0)
        errx(EXIT_FAILURE, "%s failed");
    snprintf(buf, sizeof(buf), "a %s b", "bar");
    if (strcmp(buf, "a bar b") != 0)
        errx(EXIT_FAILURE, "%s failed");

    return EXIT_SUCCESS;
}

To convert this program into an atf test program, use the template above and keep this in mind:

The result would look like:

#include <atf-c.h>
#include <stdio.h>

ATF_TC(tc, integer_formatter);
ATF_TC_HEAD(tc, integer_formatter)
{
    atf_tc_set_md_var(tc, "descr", "Validates the %d formatter");
}
ATF_TC_BODY(tc, integer_formatter)
{
    char buf[1024];

    snprintf(buf, sizeof(1024), "%d", 3);
    ATF_CHECK_STREQ("3", buf);

    snprintf(buf, sizeof(1024), "a %d b", 5);
    ATF_CHECK_STREQ("a 5 b", buf);
}

ATF_TC(tc, string_formatter);
ATF_TC_HEAD(tc, string_formatter)
{
    atf_tc_set_md_var(tc, "descr", "Validates the %s formatter");
}
ATF_TC_BODY(tc, string_formatter)
{
    char buf[1024];

    snprintf(buf, sizeof(1024), "%s", "foo");
    ATF_CHECK_STREQ("foo", buf);

    snprintf(buf, sizeof(1024), "a %s b", "bar");
    ATF_CHECK_STREQ("a bar b", buf);
}

ATF_TP_ADD_TCS(tp)
{
    ATF_TP_ADD_TC(tp, integer_formatter);
    ATF_TP_ADD_TC(tp, string_formatter);
}

Which can later be invoked as any of:

$ atf-run snprintf_test | atf-report  # Normal execution method.
$ ./snprintf_test integer_formatter  # For DEBUGGING only.
$ ./snprintf_test string_formatter  # For DEBUGGING only.

How do I write a test case for an unfixed PR?

Use the "expectations" mechanism to define part of the test case as faulty, crashy, etc. This is for two reasons:

For example, suppose we have PR lib/1 that reports a condition in which snprintf() does the wrong formatting when using %s, and PR lib/2 that mentions that another snprintf() call using %d with number 5 causes a segfault. We could do:

#include <atf-c.h>
#include <signal.h>
#include <stdio.h>

ATF_TC(tc, integer_formatter);
ATF_TC_HEAD(tc, integer_formatter)
{
    atf_tc_set_md_var(tc, "descr", "Tests the %d formatter for snprintf");
}
ATF_TC_BODY(tc, integer_formatter)
{
    char buf[1024];

    snprintf(buf, sizeof(buf), "Hello %d\n", 1);
    ATF_CHECK_STREQ("Hello 1", buf);

    atf_tc_expect_signal(SIGSEGV, "PR lib/2: %%d with 5 causes a crash");
    snprintf(buf, sizeof(buf), "Hello %d\n", 5);
    atf_tc_expect_pass();
    ATF_CHECK_STREQ("Hello 5", buf);
}

ATF_TC(tc, string_formatter);
ATF_TC_HEAD(tc, string_formatter)
{
    atf_tc_set_md_var(tc, "descr", "Tests the %s formatter for snprintf");
}
ATF_TC_BODY(tc, string_formatter)
{
    char buf[1024];

    snprintf(buf, sizeof(buf), "Hello %s\n", "world!");
    atf_tc_expect_failure("PR lib/1: %%s does not work");
    ATF_CHECK_STREQ("Hello world!", buf);
    atf_tc_expect_pass();
}

ATF_TP_ADD_TCS(tp)
{
    ATF_TP_ADD_TC(tp, integer_formatter);
    ATF_TP_ADD_TC(tp, string_formatter);
}

Do I need to remove temporary files?

No. atf-run does this automatically for you, because it runs every test program in its own temporary subdirectory.

When do I use ATF_CHECK and when ATF_REQUIRE?

ATF_CHECK logs errors but does not abort the execution of the test program. ATF_REQUIRE logs errors in a similar way but immediately terminates the execution.

You can use this distinction in the following way: use ATF_REQUIRE to check the code that "prepares" your test case. Use ATF_CHECK to do the actual functionality tests once all the set up has been performed. For example:

ATF_TC_BODY(getline) {
    FILE *f;
    char buf[1024];

    /* Opening the file is not part of the functionality under test, but it
     * must succeed before we actually test the relevant code. */
    ATF_REQUIRE((f = fopen("foo")) != NULL);

    ATF_CHECK(getline(f, buf, sizeof(buf)) > 0);
    ATF_CHECK_STREQ("line 1", buf);

    ATF_CHECK(getline(f, buf, sizeof(buf)) > 0);
    ATF_CHECK_STREQ("line 2", buf);
}
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Last edited Wednesday afternoon, September 9th, 2020
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