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Thu Sep 2 22:59:38 2010 UTC (3 years, 7 months ago) by jmmv
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Some more content and tiny improvements.  Still not done!

# Creating atf-based tests for NetBSD src

This quick tutorial is an attempt to workaround the lack of proper documentation
in atf.  The 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 a short reference of the most commonly used functions.

You should start by reading the
[tests(7)](http://netbsd.gw.com/cgi-bin/man-cgi?tests++NetBSD-current) manual
page, which is probably the only sane document in the whole documentation.  Any
other attempts at reading the atf-* manual pages are probably doomed unless you
are already familiar with atf itself and its internals.  Still, you may be able
to get some useful information out of
[atf-run(1)](http://netbsd.gw.com/cgi-bin/man-cgi?atf-run++NetBSD-current),
[atf-report(1)](http://netbsd.gw.com/cgi-bin/man-cgi?atf-report++NetBSD-current),
[atf-test-program(1)](http://netbsd.gw.com/cgi-bin/man-cgi?atf-test-program++NetBSD-current),
[atf-c-api(3)](http://netbsd.gw.com/cgi-bin/man-cgi?atf-c-api++NetBSD-current)
and
[atf-sh-api(3)](http://netbsd.gw.com/cgi-bin/man-cgi?atf-sh-api++NetBSD-current).

**IMPORTANT: Do not take anything for granted, SPECIALLY 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:

* bin/ls/fs.c: Provides the list_files() and stat_files() functions.

* bin/ls/ui.c: Provides the format_columns() function.

* bin/ls/main.c: The main method for ls.

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

* bin/ls/fs_test.c: Provides test cases for list_files and stat_files.  These
  would be named list_files__empty_directory, list_files__one_file,
  list_files__multiple_files, stat_files__directory, stat_files__symlink, etc.

* bin/ls/ui_test.c: Provides test cases for the format_columns function.  These
  would be named format_columns__no_files, format_columns__multiple_files, etc.

* bin/ls/integration_test.sh: Provides "black box" test cases for the binary
  itself.  These would be named lflag, lflag_and_Fflag, no_flags, no_files, etc.

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.

## Installation of test programs: the why and the where

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/

## 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.

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

1. Add the new test program to the Makefile.

If the subdirectory does not exist:

1. Do the same as above.

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

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

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

1. 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

    # $NetBSD: atf.mdwn,v 1.2 2010/09/02 22:59:38 jmmv Exp $

    .include <bsd.own.mk>

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

    # Define only the variables you actually need for 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

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.

Atffiles are automatically generated by bsd.test.mk, so in general you will not
have to deal with them.  However, if you have to provide one explicitly, they
follow the following 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:

    #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(returns_a_boolean()); /* Non-fatal test. */
        ATF_REQUIRE(returns_a_boolean()); /* Non-fatal test. */

        ATF_CHECK_EQ(4, 2 + 2); /* Non-fatal test. */
        ATF_REQUIRE_EQ(4, 2 + 2); /* Fatal test. */

        if (!condition)
            atf_tc_fail("Condition not met!"); /* Explicit failure. */
    }

    ATF_TC_WITHOUT_HEAD(tc, another_test_case);
    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 linked against libatf-c as described below.  Once
linked, the program automatically gains a main() method that provides a
consistent user interface to all test programs.  You are simply not inteded 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>

## Shell test programs

### Template

The following code snippet provides a shell test program with two test cases:

    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
        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_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 be executed with the atf-sh(1) interpreter as described
below.  The program automatically gains an entry point that provides a
consistent user interface to all test programs.  You are simply not inteded 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.

## 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:

* Split the whole main function into separate test cases.  In this scenario, the
  calls to printf(3) delimit a good granularity for the test cases: one for the
  integer formatter, one for the string formatter, etc.

* Use the ATF_CHECK* and/or atf_tc_fail functions to do the comparisons and
  report errors.  errx should not be used.

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:

    $ ./snprintf_test integer_formatter
    $ ./snprintf_test string_formatter
    $ atf-run snprintf_test | atf-report

### 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.

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