mutants killer - pit: state of the art of mutation testing system
TRANSCRIPT
PIT: state of the art of mutation testing system
MUTANTS KILLER
by Tàrin Gamberìni - CC BY-NC-SA 4.0
Lavora da sempre con tecnologie Java-based free e Open Source presso la Regione Emilia-Romagna
Si interessa di Object Oriented Design, Design Patterns, Build Automation, Testing e Continuous Integration
TÀRIN GAMBERÌNI
Partecipa attivamenteal Java User GroupPadova
Unit Testing
Test-Driven Development (TDD)
Continuous Integration
Code Coverage
Mutation Testing
DEVELOPMENT
UNIT TESTING & TDD
The proof of working code
Refactor with confidence (regression)
Improve code design
Living documentation
TDD extremely valuable in some context
CONTINUOUS INTEGRATION
Maintain a single source repository
Automate the build
Cheap statics for code quality
Automate unit & integration tests
Catch problems fast
LINE COVERAGE
Is a measure of tested source code
line, statement, branch, … , coverage
LINE COVERAGE 100%
Only able to identify not tested code
Doesn't check tests are able to detect faults
Measures only which code is executed by tests
WEAK TESTS
public static String foo( boolean b ) { if ( b ) { performVitallyImportantBusinessFunction(); return "OK"; } return "FAIL";}
@Testpublic void shouldFailWhenGivenFalse() { assertEquals("FAIL", foo( false ));}
@Testpublic void shouldBeOkWhenGivenTrue() { assertEquals("OK", foo( true ));}
The untested side effect
WEAK TESTS
public static String foo( boolean b ) { if ( b ) { performVitallyImportantBusinessFunction(); return "OK"; } return "FAIL";}
@Testpublic void shouldFailWhenGivenFalse() { assertEquals("FAIL", foo( false ));}
@Testpublic void shouldBeOkWhenGivenTrue() { assertEquals("OK", foo( true ));}
The untested side effect
WEAK TESTS
public static String foo( int i ) { if ( i >= 0 ) { return "foo"; } else { return "bar"; }}
@Testpublic void shouldReturnBarWhenGiven1() { assertEquals("bar", foo( 1 ));}
@Testpublic void shouldReturnFooWhenGivenMinus1() { assertEquals("foo", foo( -1 ));}
The missing boundary test
WEAK TESTS
public static String foo( int i ) { if ( i >= 0 ) { return "foo"; } else { return "bar"; }}
@Testpublic void shouldReturnBarWhenGiven1() { assertEquals("bar", foo( 1 ));}
@Testpublic void shouldReturnFooWhenGivenZero() { assertEquals("foo", foo( 0 ));}
@Testpublic void shouldReturnFooWhenGivenMinus1() { assertEquals("foo", foo( -1 ));}
The missing boundary test
WEAK TESTS
public static String foo(Collaborator c, boolean b) { if ( b ) { return c.performAction(); } return "FOO";} @Test
public void shouldPerformActionWhenGivenTrue() { foo(mockCollaborator,true); verify(mockCollaborator).performAction(); }
@Testpublic void shouldNotPerformActionWhenGivenFalse() { foo(mockCollaborator,false); verify(never(),mockCollaborator).performAction(); }
The myopic mockist
WEAK TESTS
public static String foo(Collaborator c, boolean b) { if ( b ) { return c.performAction(); } return "FOO";} @Test
public void shouldPerformActionWhenGivenTrue() { String result = foo(mockCollaborator,true); verify(mockCollaborator).performAction(); assertEquals("MOCK", result);}
@Testpublic void shouldNotPerformActionWhenGivenFalse() { String result = foo(mockCollaborator,false); verify(never(),mockCollaborator).performAction(); assertEquals("FOO", result);}
The myopic mockist
WHO TESTS THE TESTS ?
MUTATION TESTING
● originally proposed by Richard Lipton as a student in 1971
● 1st implementation tool was a PhD work in 1980
● recent availability of massive computing power has led to a resurgence
● expose weaknesses in tests (quality)
MUTATION TESTING
● originally proposed by Richard Lipton as a student in 1971
● 1st implementation tool was a PhD work in 1980
● recent availability of massive computing power has led to a resurgence
● expose weaknesses in tests (quality)
MUTATION
Is a small change in your program
MUTANT
A
mutated
version of
your
program
MUTATION TESTING
generate lots of mutants
run all tests against all mutants
check mutants: killed or lived?
MUTANT KILLED
Proof of detected mutated code Test is testing source code properly
If the unit test fails
MUTANT LIVED
Proof of not detected mutated code
If the unit test succeed
Test isn't testing source code
PIT: BASIC CONCEPTS
Applies a configurable set of mutators
Generates reports with test results
Manipulates the byte code generated by compiling your code
PIT: MUTATORSConditionals Boundary
< → <=<= → <> → >=>= → >
PIT: MUTATORSNegate Conditionals
== → !=!= → ==<= → >>= → << → >=> → <=
PIT: MUTATORSMath Mutator
+ → -- → +* → // → *% → *
& → || → &^ → &<< → >>>> → <<>>> → <<
PIT: MUTATORSRemove Conditionals
if (a == b) { // do something}
if (true) { // do something}
→
PIT: MUTATORSVoid Method Call Mutator
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
→public int foo() { int i = 5;
return i;}
public void doSomething(int i) { // does something}
PIT: MUTATORSMany others
Activated by defaultConditionals Boundary Mutator - Increments Mutator - Invert Negatives Mutator - Math Mutator - Negate Conditionals Mutator - Return Values Mutator - Void Method Calls Mutator
Deactivated by defaultConstructor Calls Mutator - Inline Constant Mutator - Non Void Method Calls Mutator - Remove Conditionals Mutator - Experimental Member Variable Mutator - Experimental Switch Mutator
HOW PIT WORKSRunning the tests
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
Your program
HOW PIT WORKSRunning the tests
PIT runs traditional line coverage analysis
HOW PIT WORKSRunning the tests
Generates mutant by applaying mutators
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
mutant 2
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
mutant 1
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
mutant 3
HOW PIT WORKSBrute force
x = 9
100 tests x 1.2ms = 0.12s
100 tests x 1.2ms x 10000 mutants = 20min !!!1000 class x 10 mutants per class = 10000 mutants
HOW PIT WORKSRunning the tests
PIT leverages line coverage to discard tests that do not exercise the mutated line of code
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
public int foo() { int i = 5; doSomething(i); return i;}
public void doSomething(int i) { // does something}
mutant 3
HOW PIT WORKSExtremely fast
x = 1
x = 1
x = 2 4 < 9
HOW PIT WORKSOutcomes
● Killed, Lived● No coverage: the same as Lived except there were no
tests that exercised the mutated line of code● Non viable: bytecode was in some way invalid● Timed Out: infinite loop● Memory error: mutation that increases the amount of
memory used● Run error: a large number of run errors probably
means something went wrong
PIT ECOSYSTEMTools
Command line
Other IDEs as a Java application
( )
EXAMPLE: LINUXDAY2015class Ticket
EXAMPLE: LINUXDAY2015testGetPrice_withAge11
EXAMPLE: LINUXDAY2015testGetPrice_withAge71
EXAMPLE: LINUXDAY2015testGetPrice_withAge18
EXAMPLE: LINUXDAY2015mvn org.pitest:pitest-maven:mutationCoverage
>> Generated 8 mutations Killed 6 (75%)>> Ran 11 tests (1.38 tests per mutation)=================================================================- Mutators=================================================================> org.pitest...ConditionalsBoundaryMutator>> Generated 2 Killed 0 (0%)> KILLED 0 SURVIVED 2 TIMED_OUT 0 NON_VIABLE 0 > MEMORY_ERROR 0 NOT_STARTED 0 STARTED 0 RUN_ERROR 0 > NO_COVERAGE 0 -----------------------------------------------------------------> org.pitest...ReturnValsMutator>> Generated 3 Killed 3 (100%)> KILLED 3 SURVIVED 0 TIMED_OUT 0 NON_VIABLE 0 > MEMORY_ERROR 0 NOT_STARTED 0 STARTED 0 RUN_ERROR 0 > NO_COVERAGE 0
EXAMPLE: LINUXDAY2015
EXAMPLE: LINUXDAY2015
EXAMPLE: LINUXDAY2015testGetPrice_withAge12
EXAMPLE: LINUXDAY2015mvn org.pitest:pitest-maven:mutationCoverage
>> Generated 8 mutations Killed 7 (88%)>> Ran 10 tests (1.25 tests per mutation)=================================================================- Mutators=================================================================> org.pitest...ConditionalsBoundaryMutator>> Generated 2 Killed 1 (50%)> KILLED 1 SURVIVED 1 TIMED_OUT 0 NON_VIABLE 0 > MEMORY_ERROR 0 NOT_STARTED 0 STARTED 0 RUN_ERROR 0 > NO_COVERAGE 0 -----------------------------------------------------------------> org.pitest...ReturnValsMutator>> Generated 3 Killed 3 (100%)> KILLED 3 SURVIVED 0 TIMED_OUT 0 NON_VIABLE 0 > MEMORY_ERROR 0 NOT_STARTED 0 STARTED 0 RUN_ERROR 0 > NO_COVERAGE 0
EXAMPLE: LINUXDAY2015
EXAMPLE: LINUXDAY2015
EXAMPLE: LINUXDAY2015testGetPrice_withAge70
EXAMPLE: LINUXDAY2015
?!?!?!?!?
EXAMPLE: LINUXDAY2015testGetPrice_withAge70
EXAMPLE: LINUXDAY2015source code on GitHub
https://github.com/taringamberini/linuxday2015.git
QUESTIONS ?
CREDITSMinion with gun - by jpartwork (no license available)https://nanookofthenerd.wordpress.com/2015/01/30/the-magnificent-maddening-marvelous-minion-episode-032/
Minion Hands on - by Ceb1031 (CC BY-SA 3.0)http://parody.wikia.com/wiki/File:Bob_minions_hands.jpg
Canon XTi components after disassembly - by particlem (CC BY 2.0)https://www.flickr.com/photos/particlem/3860278043/
Continuous Integration - by New Media Labs (no license available)http://newmedialabs.co.za/approach
Rally car - by mmphotography.it (CC BY-NC 2.0)https://www.flickr.com/photos/grantuking/9705677549/
Crash Test dummies for sale - by Jack French (CC BY-NC 2.0)https://www.flickr.com/photos/jackfrench/34523572/
Minion (no license available)http://thisandthatforkidsblog.com/2013/09/17/easy-to-make-diy-minion-halloween-pumpkin/
Images
Mutant - by minions fans-d6txvph.jpg (no license available)http://despicableme.wikia.com/wiki/File:Evil_minions_by_minions_fans-d6txvph.jpg
Mutant killed - by Patricia Uribe (no license available)http://weheartit.com/entry/70334753
Mutant lived - by Carlos Hernández (no license available)https://gifcept.com/VUQrTOr.gif
PIT logo - by Ling Yeung (CC BY-NC-SA 3.0)http://pitest.org/about/
Circled Minions - by HARDEEP BHOGAL - (no license available)https://plus.google.com/109649247879792393053/posts/ghH6tiuUZni?pid=6004685782480998482&oid=109649247879792393053
Finger puppets – by Gary Leeming (CC BY-NC-SA 2.0)https://www.flickr.com/photos/grazulis/4754781005/
Questions - by Shinichi Izumi (CC BY-SA)http://despicableme.wikia.com/wiki/File:Purple_Minion.png
CREDITSImages