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Evil Unit Testing


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Corrupt Unit Trying out

by Paul Wheaton

As a contractor, I truly earn now seemed at no longer no longer as much as six different companies beaming with satisfaction that they’ve got

“unit testing”!  And, combined with that immense satisfaction is bother that this “unit testing” is turning out to be a

disaster.  “Various of us focus on about how immense unit testing is, however this is de facto turning into painful.  The checks accumulate 45

minutes to plod, and for each and each microscopic commerce to the code, we shatter about seven checks!”

What these folks earn is a extensive pile of purposeful checks.  They fell into the favored entice of pondering that because

they plod the checks with JUnit, they should be unit checks.  90% of their considerations may per chance well earn been resolved with exact a

wee little bit of vocabulary.

Instrument Trying out Vocabulary

Unit Test: The smallest amount of testable code.   Most frequently a single blueprint/feature,

   sans the expend of different recommendations or classes.  Like a flash!  Hundreds of unit checks can plod in ten seconds or much less!

   A unit test NEVER makes expend of:

  • a database

  • an app server (or server of any form)

  • file/community I/O or file machine;

  • one other application;

  • the console (Diagram.out, Diagram.err, and tons others.)

  • logging

  • most different classes (exceptions consist of DTO’s, String, Integer, mocks and per chance a pair of others).

   Unit checks are almost gradually phase of a regression suite.

Regression Suite: A series of checks that can be plod mercurial.  An instance would

   be that every person checks build in a definite directory would all be plod by JUnit.  A developer may per chance well plod a unit test

   regression suite 20 occasions per day.  Or, they’ll also plod a purposeful test regression suite twice a month.

Helpful Test: Bigger than a unit and smaller than a full component test.

Assuredly exercising quite loads of recommendations/functions/classes working collectively.  Licensed to build up its sweet time:

a total bunch of checks may per chance well accumulate hours to plod. Most purposeful checks are phase of a purposeful test regression suite.

   Assuredly plod from JUnit.

Integration Test: Trying out two or more substances working collectively.

Most frequently phase of a regression suite.

Part Test: Running one component by itself.  Most frequently carried out by QA, managers,

   XP customers, and tons others. This earn of test is rarely any longer phase of a regression suite and it is rarely any longer plod by JUnit.

Part Acceptance Test (C.A.T.): A component test plod in front of a crowd of of us

   as phase of a proper job.  The of us in the room collectively come to a call if the component has met required requirements.

Diagram Test: All substances being plod collectively.

Diagram Acceptance Test (S.A.T.): A machine test plod in front of a crowd of of us

   as phase of a proper job.  The of us in the room collectively come to a call if the machine has met required requirements.

Stress Assessments: One other program loads a component, some substances, or per chance the entire

   machine.  I truly earn considered some microscopic stress checks worked into some regression purposeful checks – a fairly luminous potential to test

   some concurrency code!

Mock: A brain dreary piece of code atypical in unit and purposeful checks to be definite that that

   a part of code you may per chance well per chance per chance be making an try to test does no longer expend some different little bit of manufacturing code.  A Mock class now and all over again

   overrides all of the general public recommendations in a manufacturing class and is inserted someplace that would strive to expend the

   manufacturing class.  Most frequently a Mock class implements an interface and replaces manufacturing code that implements the same


Shunt: Kinda like a mock class that extends manufacturing code, handiest the rationale is NOT to

   override ALL of the recommendations, however simply ample so that you just may per chance well per chance exercise some manufacturing recommendations, whereas mocking the comfort of the

   manufacturing recommendations.  In particular important in the occasion you’ll need to test a class that would strive to expend I/O.  Your shunt can override

   the I/O recommendations whereas testing the non I/O recommendations.

And now to your change to assert the author he’s a nitwit that does no longer know the first factor about these items in the coderanch thread unit testing vocabulary.

To elaborate the amount one battle retail outlets earn with “unit testing”:

The Effort With Too Many Helpful Assessments

Originate no longer earn me adversarial.  Helpful checks earn immense mark.  I ponder apps that are successfully tested would earn a regression suite of

purposeful checks and a series of non-regression purposeful checks.  Assuredly, for each and each pound of manufacturing code, I

would truly like to gape about two pounds of unit checks and two ounces of purposeful checks (fair a microscopic bit goes a lengthy recommendations).

   The predicament I explore in too many retailers

is zero unit checks and a pound of purposeful checks.

The following two photography elaborate classes the expend of classes that expend classes.  There are purposeful checks that exercise

these classes working collectively.  Fixing a malicious program in a single class breaks many purposeful checks ….

I truly earn considered this happen many occasions.  In a single case, a microscopic commerce broke 47 checks.  Meetings were held to come to a call if the

malicious program should exact be left in the code!  Within the stay, it became as soon as made up our minds to flip off all checks till the time can be notify aside

to fix all of the checks.  Months handed.  Things purchased mighty stinky ….

The solution is to expend unit checks as a change:

The consequence is that the project is more flexible.

Helpful Test Misnomers

“By writing handiest purposeful checks, I write much less test code and exercise more manufacturing code!”  Right!  But at

   the cost of making your project brittle.  Plus, there are some finer formulation of your application that can be loads

more difficult to test with out the expend of unit checks.  The handiest coverage and flexibility can handiest be discovered by a mix of unit and

   purposeful testing that’s heavy on unit testing and gentle-weight on purposeful testing.

“My industry logic is all of those classes working collectively, so testing exact a technique is pointless.”
I am suggesting

that you just test all of the recommendations – exact individually.  Further, I am no longer suggesting that you just may per chance well per chance even earn zero purposeful checks –

they earn got their mark.

“I don’t mind if my unit test suite takes a microscopic while to plod.”
 But attain the quite loads of of us for your team mind?  Does

your team lead mind?  Your manager?  If it accumulate a microscopic while pretty than some seconds, attain you still plod the total suite a

dozen occasions a day?  At what point attain of us stop working the checks in any respect?

“A unit test is one thing plod by JUnit.”
It is elegant that in our replace, the timeframe “unit test” is subjective.  I ponder

that what I am expressing here is the most popular interpretation of the timeframe “unit test”.

Confirm out the boards at The Colossal Moose Saloon for this thread about purposeful checks vs. unit checks.

Unit Trying out Mock Basics

Right here is a extraordinarily glaring earn of unit testing.  Trying all forms of wacky stuff on a technique that does no longer depend upon

different recommendations.

Sure, any putz can unit test that earn of factor.  But most industry logic makes expend of different industry logic:

   Not handiest is this calling different industry logic, it’s calling an application server!  Perchance across a community!

   Hundreds of those are gonna accumulate higher than ten seconds.  Plus, changes in the EJB stuff may per chance well shatter my checks here!

   So a mock object desires to be introduced.

   If I could per chance well exact mock out all of the EJB stuff, I would be sitting pretty.  Hmmmm ….   If the code were to by some potential

   earn my mock FarmEJBRemote, I would be in rotund metropolis.

   First, to earn the mock.   If FarmEJBRemote were a class, I would lengthen it and override the entire recommendations.  But since

   it happens to be an interface, I will exact originate a new class and put into effect the entire recommendations:

   The mock is boring.  Truly boring.  It exact carries knowledge between my unit test and the code I am searching for to exercise.

Does this class originate you …. unlucky?  It’ll.  There are two things about this earn of class that bugged

me the first time I became as soon as uncovered to it:  The class attributes are no longer personal, and they earn got underscores in them.  The important thing

   time I saw a mock object like this

   I became as soon as knowledgeable “Your unit test code would no longer traipse into manufacturing, so it’ll decrease a pair of corners.”  I dunno … I are searching for to handiest write top quality

   code the entire time!  Not even an hour had handed and I valuable to mock java.sql.Connection.  40 recommendations!  Getters and setters for each and each

   parameter, return mark and counter for each and each blueprint?  ….  hmmmm …. pondering this by fair a microscopic ….

   the cause we originate the attributes personal is for the sake of encapsulation – to conceal how things are carried out on the

   inner so as that we are able to commerce our industry logic later with out breaking a bunch of stuff that made up our minds to tap into our

   innards.  But that does no longer truly apply to a mock, does it?  By definition, a mock has zero industry logic.  Further,

   it would no longer truly earn one thing that it didn’t exact copy from any person else.  All mock objects in every single situation may per chance well

   with out wretchedness be 100% generated at form time!  …  So I now and all over again still truly feel fair a microscopic queasy about this, however in the stay

I gradually no longer sleep re-convincing myself that this is the supreme potential.  So it is still “top quality code the entire time” – it exact

   smells fair a microscopic off.  But it completely smells better than if I did it the quite loads of potential.

Now I earn to earn the code to absorb my mock object pretty than firing up some application server.  So here’s that snippet

of code all over again and I’ve highlighted the line of code where I are searching for to expend my mock.

First, let’s separate that out pretty from the comfort of the herd …

This is gonna hurt fair a microscopic ….  I will now lengthen my manufacturing class and override getRemote() so I will be able to foist my

mock into this operation.  So I will desire to originate one microscopic commerce …

Must you may per chance well per chance per chance be a elegant OO engineer, you may be hopping enraged exact about now!  Oh sure, violating encapsulation in unit

test code is mighty unlucky, however violating encapsulation in manufacturing code JUST AIN’T DONE!  (in case you overlooked it,

   I took out the well-known phrase “personal”, making the blueprint “package personal” – now, one thing in the same package can

   explore that blueprint)   One more time, a lengthy winded clarification may per chance maybe abet accumulated things over pretty. I could set that

for the java boards and dispute for now: be ever vigilant about top quality encapsulation for your manufacturing code …

however … now and all over again … you may per chance well per chance accumulate into chronicle trading a greenback’s price of encapsulation for twenty dollars price of

testability.  And to salve your wretchedness/shame pretty, you may per chance well per chance add a comment:

Now I exact write the category so I will be able to return the mock:

Display the uncommon title:  “Shunt”.  I am no longer definite, however I ponder this notice comes from electrical engineering/tinkering

and refers to the expend of a wire to rapid total a circuit.  Initially it sounded truly unimaginative to me, however after a whereas

I purchased atypical to it.

A shunt is kinda like a mock, excluding you don’t override all of the recommendations.  This means, you mock some recommendations

whereas testing others.  A unit test may per chance well no longer sleep with quite loads of shunts all overriding the same class, each and each testing different

facets of the category.  Shunts are most frequently inner classes.

   Now for the huge finale!  The precise unit test code!

Now that the primary framework is in situation, I exact desire so that you just can add hundreds assertions.

TestFarmServlet vs. FarmServletTest:  You gotta join one camp or the quite loads of.  The folks from the latter camp originate a

   damn elegant point:  “FarmServletTest” sounds more like a noun and thus more OO.  I am in the broken-down camp.

   I truly earn change into addicted to my IDE and revel in the potential it’ll total class names

for me.  When I earn to the purpose that I truly earn a prosperous suite of checks, and my test class names all stay with “Test”,

   then my IDE makes twice as many suggestions as I need it to.  When my test class names all commence with “Test”,

my IDE makes exactly the exact series of suggestions.

Discuss these items in the discussion board thread known as Constructing Unit Assessments (with mocks and shunts!)

To earn a principle of how a project may per chance maybe handle all of these things straight, accumulate a gander at a

Sample Directory Construction

This is the earn of directory structure I explore the entire time:

Other folks build their unit test stuff in the same package as the manufacturing code they’re testing – BUT! in a different

directory structure.  So in the occasion you may per chance well per chance per chance be testing elaborate in src/java/com/javaranch/, you

may per chance well need a test class elaborate in test/unit/com/javaranch/


This is exact a transient overview of this subject.  But as soon as you may per chance well per chance even earn your head wrapped round this, you may per chance well per chance per chance be ready for

  • continuous integration

  • ant

  • bettering your layer interfaces whereas no longer sacrificing testability (static recommendations the expend of inner implementation classes)

  • testing one class or one test blueprint out of your IDE

  • test first constructing (now and all over again known as test pushed constructing) – must you attain it more, than, dispute 30% of the time?

  • Outrageous Programming!

  • Fitnesse

Discuss lost more of this earn of have in mind the testing discussion board at the spacious moose saloon.

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