1.
How to TestAsynchronous Code by Felix Geisendörfer 05.05.2011 (v1)

2.
@felixgeTwitter / GitHub / IRC

3.
Core Contributor & Module Author node-mysql node-formidable- Joined the mailing list in June 26, 2009- When I joined there where #24 people- Now mailing list has close to 4000 members members- First patch in September 2009

4.
File uploading & processing as an infrastructure service for web & mobile applications.- The app we run in production

5.
We found node

6.
TMWe found node

7.
We fell in love

8.
We had fun

9.
We crashed- Or more specifically: node crashed

10.
~1 .5 Ye Transloadit v1 a rs ag o • Complete failure • Node randomly crashed with: (evcom) recv() Success • A mess of code, hard to maintain * http://transloadit.com/blog/2010/04/to-launch-or-not- 0.1.18- New version of node took out promises- So we thought about refactoring, but ...

11.
We had no tests

12.
Time to rewrite- RailsConf 09: Robert Martin, "What Killed Smalltalk Could Kill Ruby, Too

13.
- We looked at asynchronous testing frameworks- We really wanted to do TDD- But everything we tried was hard

14.
db.query(SELECT A, function() { db.query(SELECT B, function() { db.query(SELECT C, function() { db.query(SELECT D, function() { // WTF }); }); }); });- Who here is running node in production?- Raise hands if you have a test suite for your node.js projects- Raise hands if you are happy with it- But why is it so difficult?

15.
Fold news paper 7 timesAsk audience to guess the numbers of stacked sheets of papersAsk person to guess right (128) to come up front to rip through the folded paper.What’s this about?- Newspaper can be thought of as a simple computer program managing 7 booleans- Each boolean has a meaningful impact on the behavior of the Software- This means that ripping through it at once, with a single, becomes very difficult- The problem becomes even worse when your variables have more than 2 states-> the euquation turns from being exponential into combinatoric one -> combinatoricexplosion

16.
Make it “synchronous”

17.
Version 2

18.
Well, almost : )

19.
N Transloadit v2 ow• Processed many TB of data• Very low bug rate• Clean code base, ~99% test coverage

20.
Term microtest vs Unit Test

21.
Transloadit Lines of code 13.000 9.750 6.500 3.250 0 library tests library vs test code: 1x : 2.04xLibrary: 6184 LoCTests: 12622 LoCNot included: Fixture data, server configuration, customer website, dependencies wedeveloped

22.
Transloadit Lines of code 10.000 7.500 5.000 2.500 0 integration micro integration vs. micro tests: 1x : 4.30xIntegration tests: 2254 LoCMicro Tests: 9695 LoC

23.
Transloadit Assertions 3.000 2.250 1.500 750 0 integration micro integration vs. micro tests: 1x : 12.30xIntegration tests: 189 assertsMicro Tests: 2324 asserts

24.
node-mysql Lines of code 1.700 1.275 850 425 0 library tests library vs test code: 1x : 1.35xLibrary: 1240 LoC (+600 LoC MySql constants)Tests:Tests: 1673 LoC

25.
node-mysql Lines of code 1.300 975 650 325 0 integration micro integration vs micro tests: 1x : 2.89xMicro Tests: 1243 LoCIntegration tests: 430 LoC

26.
node-mysql Assertions 400 300 200 100 0 integration micro integration vs micro tests: 1x : 8.15xMicro Tests: 375 assertsIntegration tests: 46 asserts

27.
Why do you have brakes in a car? Because then you can drive faster. Kevlin Henneyprobably Kevlin Henney, http://olvemaudal.wordpress.com/2008/04/14/being-agile-no-speeding-please/

28.
There really are only two acceptablemodels of development: "think andanalyze" or "years and years oftesting on thousands of machines". Linus Torvalds

29.
tl;dr• Don’t use integration tests to show the basic correctness of your software.• Write more microtests.

30.
Questions?

31.
Questions?