1

00:00:01,140  -->  00:00:07,620
Not let's look at assertions they are mainly about detecting errors during development and testing time

2

00:00:07,620  -->  00:00:08,370
.

3

00:00:08,370  -->  00:00:10,440
So let's see how they make that possible.

4

00:00:10,680  -->  00:00:16,760
In this listen to what assertions are along with their benefits in the next lesson they will leave office

5

00:00:16,770  -->  00:00:18,350
options.

6

00:00:19,380  -->  00:00:23,390
There are two factors that contribute to software and reliability.

7

00:00:23,670  -->  00:00:27,540
One is robustness while the other is correctness.

8

00:00:27,540  -->  00:00:34,080
Robustness is the software's ability to withstand any errors that may happen in exceptional situations

9

00:00:34,080  -->  00:00:34,980
.

10

00:00:35,010  -->  00:00:41,370
That is the software should continue to execute in such exceptional situations and we have seen throughout

11

00:00:41,400  -->  00:00:46,500
this chapter that this would be possible through exceptions and the corresponding exception handling

12

00:00:46,500  -->  00:00:47,960
mechanism.

13

00:00:47,970  -->  00:00:54,810
So what we have seen so far is all about robustness not Kirkman's as the name suggests deals with the

14

00:00:54,810  -->  00:00:57,780
software working correctly.

15

00:00:57,780  -->  00:01:01,350
And Sessions can help with correctness.

16

00:01:01,440  -->  00:01:07,620
Normally when we develop software we write a record based on what we gather from our product managers

17

00:01:07,770  -->  00:01:11,690
or any requirements documentation in the process.

18

00:01:11,850  -->  00:01:18,050
We make certain assumptions and most of the time these are options would be right but sometimes them

19

00:01:18,080  -->  00:01:24,130
emit wrongdo and it would be ideal could be kept them at development time itself.

20

00:01:25,080  -->  00:01:28,110
So an exemption would be either right or wrong.

21

00:01:28,530  -->  00:01:33,720
That is it is some kind of a boolean expression and we need to be able to test it.

22

00:01:34,140  -->  00:01:37,960
And Sessions are helpful and testing out as options.

23

00:01:37,980  -->  00:01:43,850
That is the correct method for programs and inserts statement has two forms.

24

00:01:44,040  -->  00:01:45,690
And here is the first one.

25

00:01:45,730  -->  00:01:50,350
In most keyword Essar followed by a boolean expression.

26

00:01:50,400  -->  00:01:56,340
So this statement gets the boolean expression if boolean expression evaluates to true then everything

27

00:01:56,340  -->  00:01:56,930
is good.

28

00:01:57,030  -->  00:01:59,430
Uncontrolled most of the next statement.

29

00:02:00,020  -->  00:02:03,480
Either way it implies that the program is not working correctly.

30

00:02:03,810  -->  00:02:10,100
That is there is something wrong in our assumption in this case and it is such an error is thrown.

31

00:02:10,200  -->  00:02:15,630
And the program is dominated immediately as there is no point continuing when the program is working

32

00:02:15,690  -->  00:02:17,090
incorrectly.

33

00:02:17,500  -->  00:02:23,010
As such an adder is a subclass of at a class and it is from the Dollard outline package.

34

00:02:23,010  -->  00:02:25,050
Here we have a couple of examples.

35

00:02:25,050  -->  00:02:29,630
First one is checking whether a reference variable named graph is null or not.

36

00:02:30,030  -->  00:02:33,870
If it is not then an assertion error will be wrong.

37

00:02:33,900  -->  00:02:39,530
Similarly a second example is checking whether the variable named index is greater than zero or normal

38

00:02:40,380  -->  00:02:42,200
if it is less than or equal to zero.

39

00:02:42,300  -->  00:02:45,400
And as such an order will be drawn.

40

00:02:46,200  -->  00:02:48,250
Here is the second form of Kasota statement.

41

00:02:48,430  -->  00:02:54,780
Here's the boolean expression is followed by a colon which is then followed by an error message.

42

00:02:55,020  -->  00:03:01,320
In this case if boolean expression evaluates to false then an assertion at a restaurant but is initialized

43

00:03:01,320  -->  00:03:03,250
with the error message.

44

00:03:03,300  -->  00:03:05,850
We can also see an example here.

45

00:03:06,800  -->  00:03:14,570
As for benefits assertions are very effective in quickly detecting bugs during development time and

46

00:03:14,570  -->  00:03:19,010
as a statement implies an assumption that you think is right.

47

00:03:19,530  -->  00:03:25,020
So if it fails for a particular instance of data then it means that you are as the it is wrong and you

48

00:03:25,020  -->  00:03:26,770
have to fix it.

49

00:03:27,620  -->  00:03:32,160
Moreover another might benefit as d also service documentation.

50

00:03:32,580  -->  00:03:36,420
In some situations assertions can be better than comments.

51

00:03:36,420  -->  00:03:42,360
For example let's assume that is a non-obvious competition and there is also a comment explaining it

52

00:03:42,370  -->  00:03:42,860
.

53

00:03:43,500  -->  00:03:49,650
But if some of the assumptions change and consequently the competition logic also changes then comments

54

00:03:49,650  -->  00:03:52,300
will also have to change.

55

00:03:52,470  -->  00:03:59,130
Otherwise comments would become out-of-date and hence will be out of sync with the code decisions on

56

00:03:59,130  -->  00:04:05,850
the other hand are check that on time on so would most likely fail and will force their Blipper to update

57

00:04:05,850  -->  00:04:08,070
them.

58

00:04:08,070  -->  00:04:12,590
So in that sense assertions are like active comments.

59

00:04:12,600  -->  00:04:19,130
Just the resources section where I included a few good pointers about benefits of assertions.

60

00:04:20,260  -->  00:04:26,060
Assertions can be used anywhere in the program but one good place to use them is for validating method

61

00:04:26,060  -->  00:04:27,030
parameters.

62

00:04:27,130  -->  00:04:31,890
As this particular item recommends release because this item is the last lesson.

63

00:04:31,950  -->  00:04:34,350
It's about validating metric parameters.

64

00:04:34,530  -->  00:04:39,350
If parameters have any restrictions which are also referred to as preconditions.

65

00:04:39,690  -->  00:04:43,880
So we perform some barometer checks for public methods.

66

00:04:43,950  -->  00:04:48,580
The items are just throwing an unchecked exception if there is a violation of it.

67

00:04:48,620  -->  00:04:50,330
Precondition.

68

00:04:50,520  -->  00:04:57,420
We know that this would be a programming error from the API client but for non-public methods like the

69

00:04:57,420  -->  00:05:01,590
private method the items are just using associates.

70

00:05:01,860  -->  00:05:09,490
You shouldn't use assertions for public methods for reasons one reason his assertions are disabled by

71

00:05:09,490  -->  00:05:10,370
default.

72

00:05:10,870  -->  00:05:16,080
So there wouldn't be any barometer of validity checks and consequently any programming errors from Abiah

73

00:05:16,150  -->  00:05:19,720
glance may go unnoticed.

74

00:05:19,720  -->  00:05:26,710
Second reason is assertions to the universal assertion error which might not be that helpful for API

75

00:05:26,710  -->  00:05:28,720
clients in fixing the problem.

76

00:05:29,380  -->  00:05:34,260
But for non-public methods API clients are not in working them directly.

77

00:05:34,480  -->  00:05:37,370
It is that in been the code that is invoking them.

78

00:05:37,750  -->  00:05:43,150
So the owner of the board would be expected to test them extensively during development.

79

00:05:43,250  -->  00:05:45,360
Get the help off as options.

80

00:05:45,640  -->  00:05:50,110
This way in production non-public methods should always be invoked bit.

81

00:05:50,200  -->  00:05:53,140
But I'm going to reduce.

82

00:05:53,230  -->  00:05:59,050
No if you recall when the unit is also about correctness like assertions.

83

00:05:59,340  -->  00:06:04,730
So the question would be Do we still need G-Unit or would only Jane itself wise.

84

00:06:04,930  -->  00:06:08,800
Or can we have both G-Unit as well as options.

85

00:06:08,950  -->  00:06:12,870
I would say as options would complement G-Unit what instance.

86

00:06:12,970  -->  00:06:16,980
Let's assume you do not have G-Unit on how only assertions.

87

00:06:16,990  -->  00:06:23,290
Now if you update some logic on your object and relevant assertions then how would you as the new logic

88

00:06:23,300  -->  00:06:23,880
.

89

00:06:24,210  -->  00:06:26,770
You mean tested with Vornado data instances.

90

00:06:27,110  -->  00:06:30,650
I would just hope that it would work for other kinds of The Doctor.

91

00:06:31,150  -->  00:06:37,540
But with you and it typically does the overcoaching Yes but different kinds of data in an automated

92

00:06:37,540  -->  00:06:39,370
way.

93

00:06:39,490  -->  00:06:44,590
We know that unit testing is all about automated repeatable dusting off.

94

00:06:44,590  -->  00:06:46,100
Program correctness.

95

00:06:46,410  -->  00:06:50,640
That is not if the program changes should break our desk Issus.

96

00:06:50,740  -->  00:06:54,860
So you definitely do need G-Unit also.

97

00:06:55,000  -->  00:07:01,830
G-Unit is generally about functioning of the entire metrics and not just about method parameters or

98

00:07:01,840  -->  00:07:03,850
a single statement within a method.

99

00:07:04,360  -->  00:07:10,990
So generally speaking G-Unit is about a block of code but with assertions most of the time you're dealing

100

00:07:10,990  -->  00:07:17,830
at a more granular level like a single statement or one on one method parameters but the granular level

101

00:07:17,830  -->  00:07:24,790
of testing is also important in validating our exemptions so we need both of them for program correctness

102

00:07:24,810  -->  00:07:25,070
.

103

00:07:25,380  -->  00:07:32,340
But J testing is definitely a required thing especially if you want to sleep peacefully.

104

00:07:32,350  -->  00:07:36,880
Also just note that g unit also had some kind of met that.

105

00:07:37,060  -->  00:07:37,570
Also true.

106

00:07:37,570  -->  00:07:45,040
An assertion error in case of any issues so G-Unit is making use of a standard exception as recommended

107

00:07:45,040  -->  00:07:50,890
by one of the effective dhal items which were discussed earlier.

108

00:07:50,950  -->  00:07:57,040
Finally assertions are disabled by default to ensure that they are not performance liability on production

109

00:07:57,040  -->  00:08:00,010
systems to enable them.

110

00:08:00,000  -->  00:08:06,480
The command line option hyphenate can be passed with a job lined up later as transfer enabled as options

111

00:08:06,550  -->  00:08:06,880
.

112

00:08:07,290  -->  00:08:12,280
Alternatively hyphen an able assertions can also be used.

113

00:08:12,310  -->  00:08:18,970
Assertions can be enabled disabled at specific class and package levels too put the sibling heifer India

114

00:08:19,180  -->  00:08:22,360
or hyphen miscible exceptions can be used.

115

00:08:23,250  -->  00:08:24,310
Here's an example.

116

00:08:24,400  -->  00:08:28,650
Their assertions are unable that a class level here that enabled.

117

00:08:28,690  -->  00:08:34,380
Only for the class hello and for all other classes that are disabled which as we said is their default

118

00:08:34,380  -->  00:08:35,830
behavior.

119

00:08:35,910  -->  00:08:41,700
As you can see we have the year flag followed by a colon which is in turn followed by a fully qualified

120

00:08:41,710  -->  00:08:47,530
class name and that's how you enable it for a single class.

121

00:08:47,530  -->  00:08:54,040
This example shows disabling off assertions at a class level so the previous one was an Eberling across

122

00:08:54,040  -->  00:08:54,530
level.

123

00:08:54,610  -->  00:08:57,330
Well this one is about disabling.

124

00:08:57,330  -->  00:09:04,120
Your assertions are unable dupatta you like but they are disabled only for that class Hello.

125

00:09:04,450  -->  00:09:11,630
What it means is assertions are enabled for the class Miklas on any class as it may be accessing with

126

00:09:11,640  -->  00:09:15,150
the exception of Hello class.

127

00:09:15,150  -->  00:09:20,190
No this example shows discipling of assertions at package level here.

128

00:09:20,200  -->  00:09:23,330
Assertions or anybody from my class and he grasps it.

129

00:09:23,320  -->  00:09:27,130
Maybe accessing except for all classes in the package.

130

00:09:27,120  -->  00:09:32,170
Com dot semantics career 3.0 suggest a package.

131

00:09:32,160  -->  00:09:38,320
So basically if you're dealing with specific class or package then you or be flag will be followed by

132

00:09:38,320  -->  00:09:42,310
a colon which isn't followed by class or package name.

133

00:09:42,550  -->  00:09:49,600
Just having an able flag by itself will enable assertions in Gendron having just disable flag by itself

134

00:09:49,750  -->  00:09:53,920
has no effect as as options are disabled by default.

135

00:09:54,610  -->  00:10:00,190
Ideally assertions should help in fixing all issues during development time and should be turned off

136

00:10:00,280  -->  00:10:01,670
during production.

137

00:10:02,230  -->  00:10:06,180
So that's what assertions and we will look at them off as options.

138

00:10:06,280  -->  00:10:06,730
Thank you