why unit testingl

Unit Testing

Prepared by:

Priya Sharma Trivedi

Agenda

Introduction The need of testing and it’s Terminology Unit Testing Right B.I.C.E.P.s.? Benefits of Unit Testing Naming standards for unit tests

Result of this problem error - a mistake made by a human (in a software development

activity) defect (or fault) - the result of introducing an error into a software

artifact (SRS, SDS, code, etc.) failure - a departure from the required behavior for a system

A vicious cycle – the more pressure a you (Developer) feel, the fewer tests you writes. The fewer tests you write, the less productive you are and the less stable your code becomes. The less productive and accurate you are, the more pressure you feel.

The Problem

Unit Testing Unit testing is a software verification and validation method in which a

programmer tests if individual units of source code are fit for use. The goal of unit testing is to isolate each part of the program and show that

the individual parts are correct. Unit Testing checks that behaves correctly.

Static Testing testing a unit without executing the unit code

Dynamic Testing testing a unit by executing a program unit using test data

Some common definitions of a unit: A unit is the smallest testable part of an application. In procedural programming a unit may be an individual function or

procedure. The smallest chunk that can be compiled by itself A stand alone procedure of function Something so small that it would be developed by a single person

Why Unit Testing????????????

Without unit tests defects show up in the end of development Finding them is difficult. Removing them time-consuming and Complex

With unit tests we can find defects much sooner and easier, continuously removing them before adding new features

We can also check if new features break our code

Unit Test:

Unit-tests

Should validate expected functionality at the level of:• individual class• small groups of collaborating classes• work package

Software developer

CODE

Testprograms

Automatic software test run process

• Test execution framework

• Testing naming and structure

• Test case specification template

Unit-test Component

Code Documentation

Important code should have unit tests Tests should be written together with the code Code should pass minimum 70% of the unit tests

before it can be released

Unit-test: Test frameworks

Our constrains: •TIME

Aim: to help developers:

Our inputs: •What is available as free open source code.

What we are doing:•Trying Unit Testing Tools in the our projects.• Preparing “HowTo” documents to make easier the installation of these tools and the start with process

Our plans: • Implementation of the Unit Testing Procedure in the our project environment.

• to produce code for unit-testing • to run tests in automatic way

What we propose:JUnit

NUnitSimpleTest

Unit Testing makes your developer lives easier Easier to find bugs Easier to maintain Easier to understand Easier to Develop

You have already done Unit testing Not structured Not Repeatable Not on all your code Not easy to do as it should be

A framework is missing

Designing unit tests

Type of Unit Test

Positive Test Negatives

Test the function with valid input data

Test the functionWith invalid data

When to write the test

During Development - When you need to add new functionality to the system, write the tests first. Then you will be done developing when the test runs.

During Debugging - When someone discovers a defect in your code, first write a test that will succeed if the code is working. Then debug until the test succeeds.

“Whenever you are tempted to type something into a print statement or a debugger expression, write it as a test instead.”...

An individual program unit Test for both success

& failure.For boundary

conditionsFor general

functionality Etc..

Databases, Stored

Procedures, Triggers,

Tables, Indexes

NT Services

Database conversion.OCX, .DL

L, .EXE and other

binary formatted

executables

Invariants: things that must always be true.

Post-conditions: things that must be true after you

run the code.

Pre-conditions: Those things that

must be true before you run

the code.

(Eg. The list size will always be greater than or equal to 0)

(Eg. The object’s buffer has been initialized)

(Eg. method will never return null)

(subprogram, object class, package, module)

What should be tested ?

Example of How To Think of Tests

The required functionality for a particular service (getVersionsForProductId) is the ability to get a list of all versions for a given product id. If there’s no product for that id, then an exception is thrown. If there’s no versions for a valid product id, then an empty list is returned.

The Tests That Are NeededStarting from the easiest to the hardest: If there’s no product for that id, then an exception is thrown (pre-

condition) If there’s no versions for a valid product id, then an empty list is

returned (post-condition) If there are versions for a product id, then a non-empty list of all the

versions is returned (post-condition)

Unit Testing Tasks and Steps:

Step 1: Create a Test Scenario Step 2: Create Test Cases and Test Data Step 3: If applicable create scripts to run test cases Step 4: Once the code is ready execute the test cases Step 5: Fix the bugs if any and re test the code Step 6: Repeat the test cycle until the “unit” is free of all bugs

Testing Steps

What Makes a Good Unit Test? It sufficiently tests the contract. It doesn’t need to be complete, just

“sufficient.” If it’s complex code, then have lots of tests. If it’s a simple accessor, then you don’t need a test. Most things are in between…

It runs quickly. Part of the point is to make it so that you’re able to run them regularly, so speed plays into that. It’s much easier to fix a bug you introduced five minutes ago than one

you did five weeks ago…

Tests are independent. Loosely coupled functionality enables independent tests. Write loosely coupled, highly cohesive code!

Run the tests regularly. You can be “fearless” when you need to make changes, because you

don’t have to worry that you might’ve broken something.

When to Run Tests When you write a new method……compile and run local unit tests When you fix a bug……run the test that illustrates that bug. Any successful compile……run local unit tests. Before you check in……run all tests. Continuously…...check out and build the project from scratch including

all unit tests.

Is incomplete (e.g. missing dependencies) Doesn’t compile Compiles but breaks other code Doesn’t have unit tests Has failing unit tests Passes its tests but causes other tests to fail.

Do not check in code that…

Test Case Sample

Additionally the following information may also be captured: a) Unit Name and Version Being tested b) Tested By c) Date d) Test Iteration (One or more iterations of unit testing may be performed)

Comment if any

Pass / Fail

What actually happens. This column can be omitted when defect recording tool is used.

What should happen?

Input Data

How to Test

What to Test

ID which can be referred to in other docs like “TM” “Root Cause Analysis of defects etc

RemarksPass / Fail

Actual ResultExpected Result

Input Data

TC Procedure

Test Case Purpose

Test Case

Steps to Effective Unit Testing

Documentation: Early on document all the Test Cases needed to test your code. Document the Test Cases, actual Results when executing the Test Cases, Response Time of the code for each test case. Important advantages if the test cases and the actual execution of test cases are well documented.

Documenting Test Cases prevents oversight. Documentation clearly indicates the quality of test cases. If the code needs to be retested we can be sure that we did not

miss anything. It provides a level of transparency of what was really tested during

unit testing. This is one of the most important aspects. It helps in knowledge transfer in case of employee attrition. Sometimes Unit Test Cases can be used to develop test cases for

other levels of testing

What should be tested when Unit TestingIt could be a screen or a component or a web

service

Test Cases to verify all the screen elements that need to appear on the

screens.

Test cases to verify the spelling/font/size of all the “labels” or

text that appears on the screen.

Test Cases such that every line of code in the unit is tested at least once in a

test cycle.

Test Cases such that every condition in case of “conditional statements” is

tested once.

Test Cases to test the minimum/maximum range of data that

can be entered.

Test Cases to verify how various errors are handled.

Test Cases to verify if all the validations are being performed

Never write a test that

succeeds the 1st time

Start with null case, or something

that doesn’t work

Try something trivial to

make the test work

Loose coupling &

testability go hand in hand

Use mock Objects

Write the test first

Charles' Six Rules of Unit Testing

Keep unit tests small and fast Unit tests should be fully

automated and non-interactive Make unit tests simple to run Measure the tests Fix failing tests immediately Keep testing at unit level Start off simple Keep tests independent Keep tests close to the class

being tested Name tests properly Test public API Think black-box

Think white-box Test the trivial cases too Focus on execution coverage first Cover boundary cases Provide a random generator Test each feature once Use explicit asserts Provide negative tests Design code with testing in mind Don't connect to predefined

external resources Write tests to reproduce bugs Know the limitations

Unit Testing Guidelines

Are we testing the Right B.I.C.E.P.s.?Testing without a strategy is futile.

R Are the results right?B Are all the Boundary conditions correct?

I Can you test the Inverse relationship?

C Can you Cross-check using other methods/means?

E Can you force Error conditions to happen?

P Are Performance conditions within bounds?

s Always go for the whole set.

Right-BICEP

Right: Are the results right? Validate results Does the expected result match what the method does?

If you don’t know what “right” would be, then how can you test? How do you know if your code works? Perhaps requirements not known or stable Make a decision. Your tests document what you decided.

Reassess if it changes later.

Right-BICEP

Boundary Conditions Garbage input values Badly formatted data like ’1970-23-12’ when 1970-12-23 is required. Empty or missing values (0, null, etc.) Values out of reasonable range Duplicates if they’re not allowed Unexpected orderings Totally bogus or inconsistent values, such as filenames. Validity like age in years between 0 and 90 e.g. 115. Things that arrive out of order.

Right-BICEPCheck Inverse Relationships

If your method does something that has an inverse, then apply the inverse E.g. square and square-root. Insertion then deletion.

Beware errors that are common to both your operations Seek alternative means of applying inverse if possible

Right-BICEP

Are the boundaries C.O.R.R.E.C.T.?C Conformance. Is the format Ok?O Ordering. Is the set (un)ordered as appropriate e.g. as dictated by

invariant.R Is the value within acceptable Range?R Does the code Reference anything external not under its direct control?E Does the value Exist?C Countability; Are there enough values?T Tim(e|ing). Is everything happening in the right order?

Right-BICEP

Cross-check using other means Can you do something more than one way?

Your way, and then the other way. Match? Are there overall consistency factors you can check?

Overall agreement

If e.g. you are devising a square root for an embedded system without float capability, you could test it (in the host environment) using the standard implementation, like so:

public void testSquarerootUsingStd( ) {double number=3830900.0;double root1= mySquareRoot ( number ) ;double root2= Math.sqrt ( number ) ;assertEquals ( root2 , root1 , 0.0001 ) ;}

Right-BICEP

Force Error Conditions; Can your module survive? Strange things in time keeping (like a clock that has been set back or

summer and winter time). Failures outside your code:

Invalid parameters, out of range values, etc. Out of memory, disk full, network down, etc. Can simulate such failures High system load. Limited color availability in user interface. Very high or very low screen resolution.

Right-BICEP

PerformanceA normal unit test should test for the functional requirements. But if the non-functional requirement performance or speeds depend on the size of the data, you should test that too. Perhaps absolute performance, or Perhaps how performance changes as input grows. Perhaps separate test suite in JUnit

Example: a spam filter that tests against “naughty” or black-listed mail servers. Test your code with different lists sizes. Typically a small list for build testing, but maybe also with a longer list e.g. once a day.

Benefits of Unit Testing

It provides a strict, written contract that the piece of code must satisfy.

It find problems early in the development cycle.

It allows the programmer to refactor code at a later date, and make sure the module

still works correctly (i.e. regression testing).

It may reduce uncertainty in the units themselves and can be used in a bottom-up

testing style approach.

It provides a sort of living documentation of the system. Developers looking to learn

what functionality is provided by a unit and how to use it.

By testing the parts of a program first and then testing the sum of its parts, integration

testing becomes much easier.

Result # of Test Cases (Test Development Phase) # of Test Cases Executed (Test Execution Phase) # of Test Cases Passed (Test Execution Phase) # of Test Cases Failed (Test Execution Phase) # of Test Cases Under Investigation (Test Development Phase) # of Test Cases Blocked (Test dev/execution Phase) # of Test Cases Re-executed (Regression Phase) # of First Run Failures (Test Execution Phase) Total Executions (Test Reporting Phase) Total Passes (Test Reporting Phase) Total Failures (Test Reporting Phase) Test Case Execution Time ((Test Reporting Phase) Test Execution Time (Test Reporting Phase)

Result…Cont…… % Complete % Defects Corrected % Test Coverage % Rework % Test Cases Passed % Test Effectiveness % Test Cases Blocked % Test Efficiency 1st Run Fail Rate Defect Discovery Rate Overall Fail Rate

Naming standards for unit tests

Test name should express a specific requirement. The basic naming of a test comprises of three main parts[MethodName_StateUnderTest_ExpectedBehavior]

Public void Sum_simpleValues_Calculated ()

Test name should include the expected input or state and the expected result for that input or state

Public int Sum(params int[] values), Public int Sum_NumberIsIgnored()

Test name should be presented as a statement or fact of life that expresses workflows and outputs

Public void SumNegativeNumber2()

Test Name should only begin with Test if it is required by the testing framework or if it eases development and maintenance of the unit tests in some way.

testCalculator()

Test name should include name of tested method or class.[MethodName_StateUnderTest_ExpectedBehavior]

Public void Sum_NegativeNumAs1stParam_ExcepThrown()

Variable names should express the expected input and state

BAD_DATA or EMPTY_ARRAY or NON_INITIALIZED_PERSON

Naming standards for unit tests- Cont……

Target / Subject to refer to the piece of functionality that is testing. Fixture Synonymous with "TestFixture", a fixture is a class that contains a set of

related tests. Suite Test Suites are an older style of organizing tests. They're specialized

fixtures that programmatically define which Fixtures or Tests to run.Test Methods within the Fixture that are decorated with the [Test] attribute and

contain code that validates the functionality of our target.SetUP Test Fixtures can designate a special piece of code to run before every Test

within that Fixture. That method is decorated with the [Setup] attribute. TearDown a method with the [TearDown] attribute is called at the end of every test

within a fixture. Fixture Setup Similar to constructors.

Fixture TearDown

Similar to finalizers

Category : The [Category] attribute when applied to a method associates the Test within a user-defined category.

Ignore: Tests with the [Ignore] attribute are skipped over when the Tests are run.

Explicit: Tests with the [Explicit] attribute won't run unless you manually run them.


CONSIDER: Separating your Tests from your Production Code.

If you have a requirement where you want to test in production or verify at the client's side, you can accomplish this simply by bundling the test library with your release.

CONSIDER: Deriving common Fixtures from a base Fixture

In scenarios where you are testing sets of common classes or when tests share a great deal of duplication, consider creating a base TestFixture that your Fixtures can inherit.

CONSIDER: Using Categories instead of Suites or Specialized TestsFor example, you could execute only "Stateful" tests against an environment to validate a database deployment.

Suites represent significant developer overhead and maintenance. Categories offer a unique advantage in the UI and at the command-line that allows you to specify which categories should be included or excluded from execution.

CONSIDER: Splitting Test Libraries into Multiple Assemblies

(You can always go back)

AVOID: Empty Setup methods you should only write the methods that you need today. Adding methods for future purposes only adds visual noise for maintenance purposes


DO: Name Tests after Functionality For example, a test with the name CanDetermineAuthenticatedState provides more direction about how authentication states are examined than Login.

The test name should match a specific unit of functionality for the target type being tested. Some key questions you may want to ask yourself: "what is the responsibility of this class?" "What does this class need to do?" Think in terms of action words.

DO: Document your Tests A few comments here and there are often just the right amount to help the next person understand what you need to test and how your test approaches demonstrates that functionality.

Most tests require special knowledge about the functionality your testing, so a little documentation to explain what the test is doing is helpful.

CONSIDER: Use "Cannot" Prefix for Expected Exceptions Examples: CannotAcceptNullArguments, CannotRetrieveInvalidRecord.

Since Exceptions are typically thrown when your application is a performing something it wasn't designed to do, prefix "Cannot" to tests that are decorated with the [ExpectedException] attribute.

CONSIDER: Using prefixes for Different Scenarios Some have adopted a For<Scenario> syntax (CanGetPreferencesForAnonymousUser). Other have adopted an underscore prefix _<Scenario> (AnonymousUser_CanGetPreferences).

If your application has features that differ slightly for application roles, it's likely that your test names will overlap.


AVOID: Ignore Attributes with no explanation

Tests that are marked with the Ignore attribute should include a reason for why this test has been disabled.

AVOID: Naming Tests after Implementation If you changed your method name, would the test name still make sense?

If you find that your tests are named after the methods within your classes, that's a code smell that you're testing your implementation instead of your functionality.

AVOID: Using underscores as word-separators use_underscores_as_word_separators_for_readability,

PascalCase should suffice. Imagine all the time you save not holding down the shift key.

AVOID: Unclear Test Names it's important to avoid giving them vague test names that represent a some external requirement like FixForBug133 or TestCase21.

Sometimes we create tests for bugs that are caught late in the development cycle, or tests to demonstrate requirements based on lengthy requirements documentation. As these are usually pretty important tests (especially for bugs that creep back in).


Finished with Unit Testing

CategoriesDO: Limit the number of Categories

Using Categories is a powerful way to dynamically separate your tests at runtime, however their effectiveness is diminished when developers are unsure which Category to use.

CONSIDER: Defining Custom Category Attributes

As Categories are sensitive to case and spelling, you might want to consider creating your own Category attributes by deriving from CategoryAttribute.

Summary

“Unit Testing” is the most important one. Detecting and fixing bugs early on in the Software Lifecycle helps reduce costly fixes later on. The Above article explains how Unit Testing should be done and the important points that should be considered when doing Unit Testing.

why unit testingl

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