An Introduction to Unit Testing: Reducing C/C++ bugs with Boost

An Introduction to Unit Testing: Reducing C/C++ bugs with Boost

Andrew McDonnell Software Engineer & Tech Problem Solver http://oldcomputerjunk.net [email protected] Twitter: @andymc73

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Overview ●

Software Testing

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Unit Testing

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Boost / Test

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Why Test? ●

All software has bugs

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To avoid embarrassment

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To save $$$

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Save your sanity!

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Attribution: http://www.flickr.com/photos/evelynishere/2841132210/ (CC-BY 2.0)

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In the beginning... (or not) ●

Compile and Run?

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Throw it to the users –

(the Apple Maps approach [1])

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[1] http://www.tomshardware.com/picturestory/607-ios-maps-fail.html Accessed: 22-Jan-2013

How should we Test? ●

Integration Testing

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Acceptance Testing / Feature walk throughs

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Managed alpha/beta testing

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Unit Testing

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Unit Testing Saves Hacking Time ●

Exercises low level software elements –

Classes, functions or API elements

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maintained with, and helps structure, code

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Is repeatable

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What about Open Coding...? ●

Project hackers

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Your API users

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“ If you don’t like unit testing your software, most likely your users won’t like to test it either. ”

--anonymous 8

Unit Test all the Things! (or not)

Attribution: http://xkcd.com/809 (CC-BY-NC 2.5) 9

Optimal Conditions ●

We want best bang for buck

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Wise selection of unit Test Coverage –

Comprehensive = high maintenance

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Focus on Risk areas ● ●

Complex algorithms Core modules

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Suitable Code ●

Algorithmic code

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Framework code

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Not as suitable / easy for UI elements

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Wont fix requirement defects

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Lessons Learned ●

Boost can save you a world of pain ...

Attribution:http://free-cartoons.sangrea.net/philosophy-cartoons.html (CCA-ND 2.5)

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Boost/Test ●

Boost/Test – part of the Boost C++ library

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Provides framework for expediting Unit Test

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Open source license (Boost License) http://www.boost.org/doc/libs/1_42_0/libs/test http://www.boost.org

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Boost/Test with C ●

Boost/Test is C++ –

But you can exercise C code

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Typically just wrap the C #include with ●

#ifdef __cplusplus (etc)

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There may be caveats, see online docs

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Installation ●

Installing on Linux (Debian 6, YMMV)

apt­get install libboost1.42­doc libboost­test1.42­dev

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Cross platform – also Windows, etc.

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Hello World is Easy... ●

Example Code:

#include “my_library.h” #define BOOST_TEST_MODULE HELLO_TEST #include  BOOST_AUTO_TEST_SUITE( hello_suite ) BOOST_AUTO_TEST_CASE( hello_case1 ) {   MyClass testClass(1,2);   BOOST_REQUIRE( sizeof(int) == 4 );  // specific platform   int rc = testClass.doSomething(4,5);   BOOST_CHECK_MSG( rc > 6, “Bad Value Return” ); } BOOST_AUTO_TEST_SUITE_END()

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So is Build... ●

Boost can be fully inline, simplfying linking: #include  g++ unittest.cxx ­o unittest

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This does compile much slower

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So you can also link with a library if needed ●

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Beware of #ifdefs

See also http://www.boost.org/doc/libs/1_44_0/libs/test/doc/html/faq.htm

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Header only is convient...

Attribution: http://xkcd.com/303/ (CC-BY-NC 2.5) 18

Key Features of Boost ●

Suites

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Fixtures

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Result checking

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Output Control

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Optional main()

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Test Suite ●

A means for grouping of related tests –

Provides a means of organisation

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And of identification

BOOST_AUTO_TEST_SUITE( hello_suite )

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Fixtures ●

Used to prepare generally for tests –

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e.g. (re)initialise a library

Execute before Start of all testing –

And/or Before each case

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Per Test Fixtures - example struct PerTestFixture {   PerTestFixture() { x = reset_stuff(); } // set up   ~PerTestFixture() { destroy(x); } // tear down   some_handle_t x; } BOOST_FIXTURE_TEST_CASE( case_blah, PerTestFixture) {   BOOST_CHECK(do_something()); } BOOST_FIXTURE_TEST_CASE( case_also PerTestFixture) {   BOOST_CHECK(do_something_else()); }

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The whole point - result checking ●

Running a test involves: ● ● ●

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calling code testing the output repeat the above

Use Boost macros to express expected output

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Boost has many result macros ●

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Examples: –

BOOST_CHECK(thing_is_true)

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BOOST_CHECK_GT(some_number)

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BOOST_EQUAL(a,b)

the doco is a bit confusing ●

Look under “Testing Tools / Reference”

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Control of checking ●

Three Levels –

CHECK

determines PASS or FAIL

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WARN

logs a warning

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REQUIRE

abort all tests on fail

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Choices: lots of output,or “Pass” ● ●

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Control of message detail by environment See just pass/fail, warnings, tests conducted, or detailed logs It is possible to automate and collect logs from a comprehensive suite –

And run nightly, etc.

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Where is my main() ? ●

Is hidden by test executive macros –

But you can use your own if needed

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Complementary to Unit Testing ●

Unit Testing wont find all bugs

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Source Code Inspection

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Automated linting tools, static analysis

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In Summary: ●

All software has bugs;

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You dont want to be up at 3am, so:

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(If you code in C++ (or C),)

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Use Boost/Test to Kill bugs first

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(Or any other Unit Test Framework!)

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(But Boost is Easy) 29

Credits & License ●

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Content by Andrew McDonnell @andymc73 [email protected] http://oldcomputerjunk.net http://au.linkedin.com/in/amcdonnell License: Creative Commons CC-BY-SA Images / cartoons attributed on slide

OpenOffice.org template by Raphaël Hertzog http://raphaelhertzog.com/go/ooo-template License: GPL-2+

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Test Input ●

Depends on scenario

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Generate comparison data by code in test

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Canned data

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Data generated by previous testing

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Alternative APIs

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Past good versions 31

All Software Has Bugs. (heading attribution: about three talks I attended at last years LCA !)

Attribution: 1986 BYTE Magazine Vol. 10 No. 11, p208 32

Unit Testing in Other Languages ●

Java : TestNG, JUnit

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Python : PyUnit

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PHP : PHPUnit

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Perl : Test::More

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Haskell : HUnit

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Testing doesnt fix everything ●

http://knowyourmeme.com/photos/475752tree-swing-cartoon-parodies Requirements issues ●

cheap to fix early, expensive later

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Moving on to Boost/Test ...

-

anonymous

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Obligatory Wikipedia Quote ●

According to the wisdom of the crowds [1]: “unit testing is a method by which individual units of source code, sets of one or more computer program modules together with associated control data, usage procedures, and operating procedures, are tested to determine if they are fit for use” [1] http://en.wikipedia.org/wiki/Unit_testing [Accessed 22-Jan-2013] 36