fu agile#2 unit_testing

Nguyen Ngoc [email protected] Hoa Lac, 3- 2013

mailto:[email protected]



Objectives

oWhy testing?

oBasic principles

oHow to choosing test case

oTest-First Programming

o Introduction to Junit

oLet’s do together!!!!

FUAgile: Unit Testing Basic 2


CRISIS

Numbers:4.4 million cars recalledBillions of $ loss.Damage the brand

Desire vs. Reality


Requirement\Design

Desired

Implementation

Reality

testing

gap

Why testing?

oEnsuring QUALITY

oManaging RISKS

oOptimizing Return-On-Investment (ROI)

o Professionalism


Typical Production model

Requirement

Design

Implement

Test


Bug cost


Testing level

oUnit testing

o On individual unit of source code (function, class, etc.)

o Smallest testable part

o Developer testing

o Integration testing

o On groups of modules

o System testing

o On complete integrated system


Basic Principles

oBe systematic

o Haphazard testing & exhaustive testing are impossible.

o test cases must be chosen carefully and systematically

oDo it early and often

o Don’t leave testing until the end debugging longer and

more painful

o test-first programming


Basic Principles

o Automate it

o Nothing makes tests easier to run, and more likely to be

run, than complete automation.

o For regression test


Why Testing is Hard

o We want to

o know when product is stable enough to launch

o deliver product with known failure rate (preferably low)

o offer warranty?


Why Testing is Hard

oBut

o it’s very hard to measure or ensure quality in software

o residual defect rate after shipping:

• 1 - 10 defects/kloc (typical)

• 0.1 - 1 defects/kloc (high quality: Java libraries?)

• 0.01 - 0.1 defects/kloc (very best: Praxis, NASA)

o exhaustive testing is infeasible

o statistical testing doesn’t work for software



Find bugs as cheaply and quickly as possible!

Choosing Test Cases

oKey Idea #1: Partition the Input Space

o input space is very large, but program is small so

behavior must be the “same” for whole sets of inputs

o ideal test suite

o identify sets of inputs with the same behavior

o try one input from each set


Choosing Test Cases

Ex: multiply : BigInteger x BigInteger BigInteger

partition BigInteger into:

BigNeg, SmallNeg, -1, 0, 1, SmallPos, BigPos

pick a value from each class

-265, -9 -1, 0, 1, 9, 265

test the 7 × 7 = 49 combinations


Choosing Test Cases

Ex2: max : int vs int int

partition into:

a < b, a = b, a > b

pick value from each class

(1, 2), (1, 1), (2, 1)


Choosing Test Cases

0


Choosing Test Cases

oKey idea #2: Boundary testing

o include classes at boundaries of the input space

zero, min/max values, empty set, empty string, null

o why? because bugs often occur at boundaries

o off-by-one errors

o forget to handle empty container

o overflow errors in arithmetic


Choosing Test Cases

EX: Find max value in a list of nonnegative integers. Assuming

that list is not empty.

public static int max(List<Integer> l) { ... }

list length: length 0, length 1, length 2+

max position: start, middle, end of list

value of max: MIN_INT, negative, 0, positive, MAX_INT


Coverage

o all-statements: is every statement run by some test case?

(common goal)

o all-branches: if every direction of an if or while statement (true

or false) taken by some test case?

o all-paths: is every possible combination of branches – every

path through the program – taken by some test case?


Test-first programming

2 approaches:

Code Tests Fix bugs (painful)

Write tests Code



What is your choice?


write tests before coding

specifically, for every method or class:

1) write specification

2) write test cases that cover the spec

3) implement the method or class

4) once the tests pass (and code coverage is sufficient), you’re done


JUnit

oUnit testing automation framework for Java

oCan do integration test

o Integrated in IDEs (Eclipse, NetBeans, IntelliJ, etc.)

oMust have tool for Java developers


http://www.junit.org/

JUnit

oA JUnit test case start with @Test

oTest case name start with testXXX()

oUsing assertEquals, assertTrue, assertFalse…

@Test

public void testMaxAtStart(){

ArrayList<Integer> list = new ArrayList<>();

//add 5,2,3 to list

assertEquals(MyClass.Max(list), 5);

}FUAgile: Unit Testing Basic 24

JUnit

o If you expect an exception using

@Test(expected = SomeTypeOfException.class)

@Test(expected = IllegalArgumentException.class)

public void testMaxAtStart(){

ArrayList<Integer> list = new ArrayList<>();

MyClass.Max(list)

}


Let’s do togetherUsing Test-First programming

Ex1: Write a function with parameter is an integer n, if n<0 throw

IllegalArgumentException; otherwise

• if n%3==0 return “Fizz”;

• If n%5==0 return “Buzz”;

• If n%3==0 and n%5==0 return “FizzBuzz”;

• Else return the number itself

public static String fizzBuzz(int n) { ... }


Let’s do together

Using Test-First programming

Ex2: Find max value in a list of nonnegative integers. Assuming

that list is not empty.

public static int max(List<Integer> list) { ... }


Let’s do together

Using Test-First programming

Ex3: Find the union of 2 arrays of integers.

public static int[] union(int[] arr1, int[] arr2) { ... }


fu agile#2 unit_testing

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