The document discusses mutation testing as a way to write better unit tests. Mutation testing involves making small changes or "mutations" to the production code and then running the test suite to see if the tests can detect the changes, or "kill" the mutations. It is recommended to generate mutants, run the unit tests, check the reports, and write more or improved tests until reaching a quality target where most or all mutants are killed. Different types of common code mutations are discussed such as replacing operators, variables, or removing conditionals. The goal of mutation testing is to help write a test suite that can detect as many small defects as possible in the code.

1. prepare for…
Mutation Testing
..from jUnit to Mutation-Testing

2. @SvenRuppert
has been coding java since 1996
Fellow / Head of R&D
reply Group
Germany - Munich
2

3. @SvenRuppert
has been coding java since 1996
3

4. @SvenRuppert
has been coding java since 1996
Projects in the field of:
•Automobile-industry
•Energy
•Finance / Leasing
•Space- Satellit-
•Government / UN / World-bank
Where?
•Europe
•Asia - from India up to Malaysia
3

5. 4
Save harbor statement

6. 4
Save harbor statement
The following is intended for information purposes only. I
can not be held responsible for the overuse of effects and
animations in this presentation. If any person in this room
has a medical condition that is triggered by fast moving
objects on the screen and/or explosions, he/she should
probably better leave now…
(I got carried away by the topic.)

7. 5
The Environment @SvenRuppert
Codebase is > 13 years old

8. 5
The Environment @SvenRuppert
Codebase is > 13 years old
no test coverage

9. 5
The Environment @SvenRuppert
Codebase is > 13 years old
no test coverage
no dedicated refactoring budget

10. 5
The Environment @SvenRuppert
Codebase is > 13 years old
no test coverage
no dedicated refactoring budget
decrease complexity

11. 5
The Environment @SvenRuppert
Codebase is > 13 years old
no test coverage
no dedicated refactoring budget
decrease complexity
but… lets start with the basics

12. 6
TDD with jUnit @SvenRuppert

13. 6
TDD with jUnit @SvenRuppert
are you using jUnit?

14. 6
TDD with jUnit @SvenRuppert
are you using jUnit?
assume that the following would make sense.. ;-)

15. 6
TDD with jUnit @SvenRuppert
are you using jUnit?
assume that the following would make sense.. ;-)
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}

16. 6
TDD with jUnit @SvenRuppert
are you using jUnit?
assume that the following would make sense.. ;-)
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?

17. 6
TDD with jUnit @SvenRuppert
are you using jUnit?
assume that the following would make sense.. ;-)
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
it depends ;-)

18. 7
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
it depends ;-)

19. 7
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
it depends ;-)
for line 100% coverage

20. 7
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
it depends ;-)
for line 100% coverage 2

21. 7
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
it depends ;-)
for line 100% coverage 2
but will this be enough?

22. 7
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
it depends ;-)
for line 100% coverage 2
but will this be enough? No

23. 8
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
for line 100% coverage 2
but will this be enough? No
it depends ;-)

24. 8
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
for line 100% coverage 2
but will this be enough? No
how to find out, what will be enough?
it depends ;-)

25. 8
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
for line 100% coverage 2
but will this be enough? No
how to find out, what will be enough?
how to find the right tests?
it depends ;-)

26. 9
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?

27. 9
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
@Test
public void testAdd001() throws Exception {
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
}

28. 9
TDD with jUnit @SvenRuppert
public class Service {
public int add(int a, int b){
if(a<2){
return (a+b) * -1;
} else {
return a+b;
}
}
}
How many tests
you will need ?
@Test
public void testAdd001() throws Exception {
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
}
@Test
public void testAdd002() throws Exception {
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);
}

29. 10
Mutation Testing @SvenRuppert

30. 10
Mutation Testing @SvenRuppert
Mutation Testing is a structural testing method

31. 10
Mutation Testing @SvenRuppert
Mutation Testing is a structural testing method
we want to find a way to write "good" tests

32. 10
Mutation Testing @SvenRuppert
Mutation Testing is a structural testing method
we want to find a way to write "good" tests
how to find "good" tests?

33. 10
Mutation Testing @SvenRuppert
Mutation Testing is a structural testing method
we want to find a way to write "good" tests
how to find "good" tests?
let the machine find the targets

34. 10
Mutation Testing @SvenRuppert
Mutation Testing is a structural testing method
we want to find a way to write "good" tests
how to find "good" tests?
let the machine find the targets
let´s mutate it... but how?

35. 11
Mutation Testing - the Idea @SvenRuppert

36. 11
Mutation Testing - the Idea @SvenRuppert
a mutation is a small change in the code

37. 11
Mutation Testing - the Idea @SvenRuppert
a mutation is a small change in the code
.. small enough to be a small defect

38. 11
Mutation Testing - the Idea @SvenRuppert
a mutation is a small change in the code
.. small enough to be a small defect
P will be the program

39. 11
Mutation Testing - the Idea @SvenRuppert
a mutation is a small change in the code
.. small enough to be a small defect
P will be the program
T will be the collection of all tests / Test Suite

40. 12
Mutation Testing - the Idea @SvenRuppert
P will be the program
T will be the collection of all tests / Test Suite

41. 12
Mutation Testing - the Idea @SvenRuppert
P will be the program
T will be the collection of all tests / Test Suite
we will create a sequence of mutations / P1,P2,P3...

42. 12
Mutation Testing - the Idea @SvenRuppert
P will be the program
T will be the collection of all tests / Test Suite
we will create a sequence of mutations / P1,P2,P3...
.. Px will have only one mutation compared to P

43. 12
Mutation Testing - the Idea @SvenRuppert
P will be the program
T will be the collection of all tests / Test Suite
we will create a sequence of mutations / P1,P2,P3...
.. Px will have only one mutation compared to P
running all tests from T against Px

44. 12
Mutation Testing - the Idea @SvenRuppert
P will be the program
T will be the collection of all tests / Test Suite
we will create a sequence of mutations / P1,P2,P3...
.. Px will have only one mutation compared to P
running all tests from T against Px
green: T will kill the mutation

45. 12
Mutation Testing - the Idea @SvenRuppert
P will be the program
T will be the collection of all tests / Test Suite
we will create a sequence of mutations / P1,P2,P3...
.. Px will have only one mutation compared to P
running all tests from T against Px
green: T will kill the mutation
.. at leased one test from T will fail

46. 12
Mutation Testing - the Idea @SvenRuppert
P will be the program
T will be the collection of all tests / Test Suite
we will create a sequence of mutations / P1,P2,P3...
.. Px will have only one mutation compared to P
running all tests from T against Px
green: T will kill the mutation
.. at leased one test from T will fail
red: if all tests are green

47. 13
Mutation Testing - the Idea @SvenRuppert

48. 13
Mutation Testing - the Idea @SvenRuppert
if we kill k out of n mutants

49. 13
Mutation Testing - the Idea @SvenRuppert
if we kill k out of n mutants
-> we are not good enough ;-)

50. 13
Mutation Testing - the Idea @SvenRuppert
if we kill k out of n mutants
-> we are not good enough ;-)
we are perfect enough if we are reaching : k == n

51. 13
Mutation Testing - the Idea @SvenRuppert
if we kill k out of n mutants
-> we are not good enough ;-)
we are perfect enough if we are reaching : k == n
how to create all versions of Px ?

52. 13
Mutation Testing - the Idea @SvenRuppert
if we kill k out of n mutants
-> we are not good enough ;-)
we are perfect enough if we are reaching : k == n
how to create all versions of Px ?
.. the good thing..

53. 13
Mutation Testing - the Idea @SvenRuppert
if we kill k out of n mutants
-> we are not good enough ;-)
we are perfect enough if we are reaching : k == n
how to create all versions of Px ?
.. the good thing..
we could almost generate/
automate everything

54. 14
Mutation Testing @SvenRuppert
practical TDD with Mutation Testing

55. 14
Mutation Testing @SvenRuppert
generating the mutants and
practical TDD with Mutation Testing

56. 14
Mutation Testing @SvenRuppert
generating the mutants and
practical TDD with Mutation Testing
running all junit tests

57. 14
Mutation Testing @SvenRuppert
generating the mutants and
practical TDD with Mutation Testing
running all junit tests
check the reports

58. 14
Mutation Testing @SvenRuppert
generating the mutants and
practical TDD with Mutation Testing
running all junit tests
check the reports
write more / better tests

59. 14
Mutation Testing @SvenRuppert
generating the mutants and
practical TDD with Mutation Testing
running all junit tests
check the reports
write more / better tests
loop until quality target reached

60. 15
Mutation Testing @SvenRuppert
mutants are a good approach / model to estimate
the default rate of defects per 1k lines of the P

61. 15
Mutation Testing @SvenRuppert
mutants are a good approach / model to estimate
the default rate of defects per 1k lines of the P
estimate that:

62. 15
Mutation Testing @SvenRuppert
mutants are a good approach / model to estimate
the default rate of defects per 1k lines of the P
estimate that:
the defects are independent

63. 15
Mutation Testing @SvenRuppert
mutants are a good approach / model to estimate
the default rate of defects per 1k lines of the P
estimate that:
the defects are independent normaly ;-)

64. 16
Mutation Testing @SvenRuppert

65. 16
Mutation Testing @SvenRuppert
no need to know that Mutation Testing will be done,
independend creation of T

66. 16
Mutation Testing @SvenRuppert
no need to know that Mutation Testing will be done,
independend creation of T
for K==n
we need a high number of mutants ( P1, P2, .., Px)

67. 16
Mutation Testing @SvenRuppert
no need to know that Mutation Testing will be done,
independend creation of T
for K==n
we need a high number of mutants ( P1, P2, .., Px)
.. mostly it will lead into exponential numbers of Px

68. 16
Mutation Testing @SvenRuppert
no need to know that Mutation Testing will be done,
independend creation of T
for K==n
we need a high number of mutants ( P1, P2, .., Px)
.. mostly it will lead into exponential numbers of Px
.. how to find YOUR barrier you
have to reach?

69. 16
Mutation Testing @SvenRuppert
no need to know that Mutation Testing will be done,
independend creation of T
for K==n
we need a high number of mutants ( P1, P2, .., Px)
.. mostly it will lead into exponential numbers of Px
.. how to find YOUR barrier you
have to reach?
but.. what is a mutation?

70. 17
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation
changing constants,
loop bounds (adding/subtracting values)

71. 18
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation
Decision Mutation
for example < will be changed to <=

72. 19
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation Decision Mutation
for example swapping/deleting/duplicating
lines of code
Statement Mutation

73. 20
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation Decision Mutation
Statement Mutation

74. 20
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation Decision Mutation
Statement Mutation
for Java you could think about more
language spec. mutations

75. 20
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation Decision Mutation
Statement Mutation
for Java you could think about more
language spec. mutations
.. changing modifiers

76. 20
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation Decision Mutation
Statement Mutation
for Java you could think about more
language spec. mutations
.. changing modifiers
.. changing between static / non static

77. 20
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation Decision Mutation
Statement Mutation
for Java you could think about more
language spec. mutations
.. changing modifiers
.. changing between static / non static
.. delete member initialization

78. 20
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation Decision Mutation
Statement Mutation
for Java you could think about more
language spec. mutations
.. changing modifiers
.. changing between static / non static
.. delete member initialization
.. delete this.

79. 20
Mutation Testing - Kinds of Mutation @SvenRuppert
but.. what is a mutation?
Value Mutation Decision Mutation
Statement Mutation
for Java you could think about more
language spec. mutations
.. changing modifiers
.. changing between static / non static
.. delete member initialization
.. delete this.
.. argument order change

80. 21
Mutation Testing - in short words @SvenRuppert

81. 21
Mutation Testing - in short words @SvenRuppert
mutation testing is an add on to normal jUnit TDD

82. 21
Mutation Testing - in short words @SvenRuppert
mutation testing is an add on to normal jUnit TDD
tools are supporting it well

83. 21
Mutation Testing - in short words @SvenRuppert
mutation testing is an add on to normal jUnit TDD
tools are supporting it well
generating and running all tests are time consuming

84. 21
Mutation Testing - in short words @SvenRuppert
mutation testing is an add on to normal jUnit TDD
tools are supporting it well
generating and running all tests are time consuming
but most important

85. 21
Mutation Testing - in short words @SvenRuppert
mutation testing is an add on to normal jUnit TDD
tools are supporting it well
generating and running all tests are time consuming
but most important
will effect your project structure

86. 22
Mutation Testing - Frameworks @SvenRuppert

87. 22
Mutation Testing - Frameworks @SvenRuppert
muJava

88. 22
Mutation Testing - Frameworks @SvenRuppert
muJava
2003. First released as JMutation (Java Mutation System).
2004. The name was changed to MuJava (Mutation System for Java).
2005. Software Copyright Registration, ALL RIGHTS RESERVED.
2005. Version 2 released with several fault fixes and modified mutation operators.
2008. Version 3 released with minimal support for Java 1.5 and 1.6.
2013. Version 4 released to support JUnit tests and Java 1.6 language features, including generics,
annotations, enumerations, varargs, enhanced for-each loops, and static imports.
2015. Additional and improved error messages. Bug fixes for OpenJava. Licensing changed to the
Apache license.

89. 22
Mutation Testing - Frameworks @SvenRuppert
muJava
2003. First released as JMutation (Java Mutation System).
2004. The name was changed to MuJava (Mutation System for Java).
2005. Software Copyright Registration, ALL RIGHTS RESERVED.
2005. Version 2 released with several fault fixes and modified mutation operators.
2008. Version 3 released with minimal support for Java 1.5 and 1.6.
2013. Version 4 released to support JUnit tests and Java 1.6 language features, including generics,
annotations, enumerations, varargs, enhanced for-each loops, and static imports.
2015. Additional and improved error messages. Bug fixes for OpenJava. Licensing changed to the
Apache license.
https://cs.gmu.edu/~offutt/mujava/
https://github.com/jeffoffutt/muJava/graphs/contributors

90. 22
Mutation Testing - Frameworks @SvenRuppert
muJava
2003. First released as JMutation (Java Mutation System).
2004. The name was changed to MuJava (Mutation System for Java).
2005. Software Copyright Registration, ALL RIGHTS RESERVED.
2005. Version 2 released with several fault fixes and modified mutation operators.
2008. Version 3 released with minimal support for Java 1.5 and 1.6.
2013. Version 4 released to support JUnit tests and Java 1.6 language features, including generics,
annotations, enumerations, varargs, enhanced for-each loops, and static imports.
2015. Additional and improved error messages. Bug fixes for OpenJava. Licensing changed to the
Apache license.
https://cs.gmu.edu/~offutt/mujava/
https://github.com/jeffoffutt/muJava/graphs/contributors
inactive

91. 23
Mutation Testing - Frameworks @SvenRuppert

92. 23
Mutation Testing - Frameworks @SvenRuppert
2012. started around 2012 with a small codebase.
2014. very active since 2014

93. 23
Mutation Testing - Frameworks @SvenRuppert
2012. started around 2012 with a small codebase.
2014. very active since 2014
http://pitest.org/

94. 23
Mutation Testing - Frameworks @SvenRuppert
2012. started around 2012 with a small codebase.
2014. very active since 2014
http://pitest.org/
active ;-)

95. 24
Mutation Testing - Hello World @SvenRuppert
http://pitest.org/

96. 24
Mutation Testing - Hello World @SvenRuppert
http://pitest.org/
assume the following would make sense ;-)

97. 24
Mutation Testing - Hello World @SvenRuppert
http://pitest.org/
assume the following would make sense ;-)
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
}

98. 25
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
}

99. 25
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
} how many test you will need for..

100. 25
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
} how many test you will need for..
100% Line Coverage… and…

101. 25
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
} how many test you will need for..
100% Line Coverage… and… to be save ?

102. 25
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
} how many test you will need for..
100% Line Coverage… and… to be save ?
2 for Line Coverage

103. 25
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
} how many test you will need for..
100% Line Coverage… and… to be save ?
2 for Line Coverage we will see ;-)

104. 26
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
}
100% Line Coverage… and…

105. 26
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
}
100% Line Coverage… and…
we have one if statement

106. 26
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
}
100% Line Coverage… and…
we have one if statement with an else branch

107. 26
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) {
return (a+b) * -1;
} else {
return a+b;
}
}
}
100% Line Coverage… and…
we have one if statement with an else branch
this will lead to 2 jUnit Tests to get 100 %

108. 27
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) { return (a+b) * -1; }
else { return a+b; }
}
} 100% Line Coverage… and…

109. 27
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) { return (a+b) * -1; }
else { return a+b; }
}
} 100% Line Coverage… and…
@Test
public void testAdd001() throws Exception {
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
}

110. 27
Mutation Testing - Hello World @SvenRuppert
public class Service {
public int add(int a, int b){
if (a<2) { return (a+b) * -1; }
else { return a+b; }
}
} 100% Line Coverage… and…
@Test
public void testAdd001() throws Exception {
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
}
@Test
public void testAdd002() throws Exception {
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);
}

111. 28
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);

112. 28
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);

113. 28
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);

114. 29
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);

115. 29
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);
we got 100% Line Coverage

116. 29
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);
we got 100% Line Coverage
How good these tests are?

117. 29
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);
we got 100% Line Coverage
How good these tests are?
How to measure if these test are good?

118. 29
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
Assertions.assertThat(add).isEqualTo(0);
final int add = new Service().add(3, 0);
Assertions.assertThat(add).isEqualTo(3);
we got 100% Line Coverage
How good these tests are?
How to measure if these test are good?
How to find the good tests?

119. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?

120. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?
let´s generate a the mutation report

121. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?
let´s generate a the mutation report
with maven : pitest: mutationCoverage

122. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?
let´s generate a the mutation report
with maven : pitest: mutationCoverage
>> Generated 54 mutations

123. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?
let´s generate a the mutation report
with maven : pitest: mutationCoverage
>> Generated 54 mutations Killed 3 (6%)

124. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?
let´s generate a the mutation report
with maven : pitest: mutationCoverage
>> Generated 54 mutations
org.pitest……mutators.ConditionalsBoundaryMutator
Killed 3 (6%)

125. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?
let´s generate a the mutation report
with maven : pitest: mutationCoverage
>> Generated 54 mutations
org.pitest……mutators.ConditionalsBoundaryMutator
org.pitest……mutators.IncrementsMutator
Killed 3 (6%)

126. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?
let´s generate a the mutation report
with maven : pitest: mutationCoverage
>> Generated 54 mutations
org.pitest……mutators.ConditionalsBoundaryMutator
org.pitest……mutators.IncrementsMutator
org.pitest……mutators.ReturnValsMutator
Killed 3 (6%)

127. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?
let´s generate a the mutation report
with maven : pitest: mutationCoverage
>> Generated 54 mutations
org.pitest……mutators.ConditionalsBoundaryMutator
org.pitest……mutators.IncrementsMutator
org.pitest……mutators.ReturnValsMutator
org.pitest……mutators.MathMutator
Killed 3 (6%)

128. 30
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
How to find the good tests?
let´s generate a the mutation report
with maven : pitest: mutationCoverage
>> Generated 54 mutations
org.pitest……mutators.ConditionalsBoundaryMutator
org.pitest……mutators.IncrementsMutator
org.pitest……mutators.ReturnValsMutator
org.pitest……mutators.MathMutator
org.pitest……mutators.NegateConditionalsMutator
Killed 3 (6%)

129. 31
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations Killed 3 (6%)

130. 31
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations Killed 3 (6%)

131. 31
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations Killed 3 (6%)

132. 32
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations Killed 3

133. 32
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations Killed 3

134. 32
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations Killed 3

135. Killed 3
33
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations

136. Killed 3
33
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations
final int add = new Service().add(2, 0);

137. 33
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations
final int add = new Service().add(2, 0);

138. Killed 4
33
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations
final int add = new Service().add(2, 0);

139. Killed 4
33
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations
final int add = new Service().add(2, 0);

140. Killed 4
33
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations
final int add = new Service().add(2, 0);

141. Killed 4
33
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
final int add = new Service().add(3, 0);
>> Generated 54 mutations
final int add = new Service().add(2, 0);

142. Killed 4
33
Mutation Testing - Hello World @SvenRuppert
final int add = new Service().add(0, 0);
>> Generated 54 mutations
final int add = new Service().add(2, 0);

143. Killed 4
33
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);

144. Killed 4
34
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);

145. Killed 4
34
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);

146. 34
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);

147. Killed 5
34
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);

148. Killed 5
34
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);
killed 9:1

149. Killed 5
35
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);
killed 9:1

150. Killed 5
35
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);
killed 9:1
final int add = new Service().add(2, 2);

151. 35
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);
killed 9:1
final int add = new Service().add(2, 2);

152. Killed 6
35
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);
killed 9:1
final int add = new Service().add(2, 2);

153. Killed 6
35
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);
killed 9:1
final int add = new Service().add(2, 2);

154. Killed 6
35
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);
killed 9:1
final int add = new Service().add(2, 2);

155. Killed 6
35
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(2, 0);
final int add = new Service().add(1, 1);
final int add = new Service().add(2, 2);
killed 11:1

156. Killed 6
35
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(1, 1);
final int add = new Service().add(2, 2);
killed 11:1

157. Killed 6
36
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(1, 1);
final int add = new Service().add(2, 2);

158. Killed 6
36
Mutation Testing - Hello World @SvenRuppert
>> Generated 54 mutations
final int add = new Service().add(1, 1);
final int add = new Service().add(2, 2);

159. 37
Mutation Testing - Lesson Learned @SvenRuppert

160. 37
Mutation Testing - Lesson Learned @SvenRuppert
mutation tests are often leading to

161. 37
Mutation Testing - Lesson Learned @SvenRuppert
mutation tests are often leading to
…cleaner code compared to jUnit only

162. 37
Mutation Testing - Lesson Learned @SvenRuppert
mutation tests are often leading to
…cleaner code compared to jUnit only
… smaller modules (shorter mutation runtime)

163. 37
Mutation Testing - Lesson Learned @SvenRuppert
mutation tests are often leading to
…cleaner code compared to jUnit only
… smaller modules (shorter mutation runtime)
and something nice…
helps to find useless code

164. 38
Example of useless Code @SvenRuppert

165. 38
Example of useless Code @SvenRuppert

166. 38
Example of useless Code @SvenRuppert

167. 39
Mutation Testing - How to start @SvenRuppert

168. 39
Mutation Testing - How to start @SvenRuppert
you need jUnit - to generate the reference

169. 39
Mutation Testing - How to start @SvenRuppert
you need jUnit - to generate the reference
add the pitest-plugin to the build section

170. 39
Mutation Testing - How to start @SvenRuppert
you need jUnit - to generate the reference
add the pitest-plugin to the build section
configure the plugin

171. 39
Mutation Testing - How to start @SvenRuppert
you need jUnit - to generate the reference
add the pitest-plugin to the build section
configure the plugin
generate the reference -> clean , install

172. 39
Mutation Testing - How to start @SvenRuppert
you need jUnit - to generate the reference
add the pitest-plugin to the build section
configure the plugin
generate the reference -> clean , install
run pitest: mutationCoverage

173. 39
Mutation Testing - How to start @SvenRuppert
you need jUnit - to generate the reference
add the pitest-plugin to the build section
configure the plugin
generate the reference -> clean , install
run pitest: mutationCoverage
report will be under target/pit-reports

174. 40
Mutation Testing - How to start @SvenRuppert
pom.xml - example - build
<plugin>
<groupId>org.pitest</groupId>
<artifactId>pitest-maven</artifactId>
<configuration>
<outputFormats>
<outputFormat>XML</outputFormat>
<outputFormat>HTML</outputFormat>
</outputFormats>
<targetClasses>
<param>org.rapidpm.*</param>
</targetClasses>
<targetTests>
<param>org.rapidpm.*</param>
<param>junit.org.rapidpm.*</param>
</targetTests>
</configuration>
</plugin>

175. 41
Mutation Testing - How to start @SvenRuppert
pom.xml - example - reporting
<reporting>
<plugins>
<plugin>
<groupId>org.pitest</groupId>
<artifactId>pitest-maven</artifactId>
<reportSets>
<reportSet>
<reports>
<report>report</report>
</reports>
</reportSet>
</reportSets>
</plugin>
</plugins>
</reporting>

176. 42
Mutation Testing - practical usage @SvenRuppert

177. 42
Mutation Testing - practical usage @SvenRuppert
Start with some tests

178. 42
Mutation Testing - practical usage @SvenRuppert
Start with some tests
generate the pitest report

179. 42
Mutation Testing - practical usage @SvenRuppert
Start with some tests
generate the pitest report
write more tests to kill mutations

180. 42
Mutation Testing - practical usage @SvenRuppert
Start with some tests
generate the pitest report
write more tests to kill mutations
if you have time, eliminate useless tests

181. 42
Mutation Testing - practical usage @SvenRuppert
Start with some tests
generate the pitest report
write more tests to kill mutations
if you have time, eliminate useless tests
do it one by one

182. 42
Mutation Testing - practical usage @SvenRuppert
Mutation 001
Mutation 002
Mutation 003
Mutation 004 Survived
Survived
Survived
Survived
Start with some tests
generate the pitest report
write more tests to kill mutations
if you have time, eliminate useless tests
do it one by one

183. 42
Mutation Testing - practical usage @SvenRuppert
Mutation 001
Mutation 002
Mutation 003
Mutation 004 Survived
Killed
Survived
Survived
Survived
Killed
Killed
Killed
Start with some tests
generate the pitest report
write more tests to kill mutations
if you have time, eliminate useless tests
do it one by one

184. Summary
43
@SvenRuppert
If you are interested…
have a look at GITHUB
ProxyBuilder
Dynamic-Dependency-Injection
Java-Microservice
or contact me ;-) @SvenRuppert

185. Summary
43
@SvenRuppert
If you are interested…
have a look at GITHUB
ProxyBuilder
Dynamic-Dependency-Injection
Java-Microservice
or contact me ;-) @SvenRuppert
Thank You !!!