Test-Driven Development in JavaScript

Test-Driven Development
turn development on its head

Aaron Nordyke
Sr. Software Engineer
Innovations Development

If I were being
completely honest,
there’s been a
consistent pattern in
my projects.

Dirty Code

Zero Unit Tests

Low Test Coverage

Stupid Bugs

Fear Of Breaking Anything

Dirty Code
function fillXigrisRelative(){
try {
var at = _g("relativeTable");
//var docfrag = document.createDocumentFragment();
Big functions
//INR > 3.0 - PTT > 40 sec
//INR
ea = getEvents("sep_inr_ec", SEPSISREPLY);
for (i = 0; i < ea.length; i++) {
for (j = 0; j < SEPSISREPLY.VALUES[ea[i]].EVENTS.length; j++) {
event_dt = SEPSISREPLY.VALUES[ea[i]].EVENTS[j].EVENTDTDISP;
disp = SEPSISREPLY.VALUES[ea[i]].EVENTS[j].EVENT_DISP;
rslt = SEPSISREPLY.VALUES[ea[i]].EVENTS[j].EVENT_RESULT;
xigrisNotify(_g("inrptt_notify"), [disp, rslt, event_dt]);
if (SEPSISREPLY.VALUES[ea[i]].EVENTS[j].RSLTVAL > 3.0) {
_g("rel_inrptt_form").ynu[0].checked = true;
}
}
}
//PTT
ea = getEvents("sep_ptt_ec", SEPSISREPLY);
xigrisNotify(_g("inrptt_notify"), [disp, rslt, event_dt]);
if (SEPSISREPLY.VALUES[ea[i]].EVENTS[j].RSLTVAL > 40) {
_g("rel_inrptt_form").ynu[0].checked = true;
}
}
}
…

Dirty Code
//Platelet Count
ea = getEvents("sep_plt_ec", SEPSISREPLY);
…that keep going
xigrisNotify(_g("platelet_notify"), [disp, rslt, event_dt]);
if (SEPSISREPLY.VALUES[ea[i]].EVENTS[j].RSLTVAL < 30000) {
_g("rel_platelet_form").ynu[0].checked = true;
}
}
}
//Gastro-intestinal bleed
ea = getEvents("sep_gi_hem_dx", SEPSISREPLY);
disp = SEPSISREPLY.VALUES[ea[i]].VALEVENTFTX;
rslt = SEPSISREPLY.VALUES[ea[i]].VALEVENTNOMDISP;
event_dt = SEPSISREPLY.VALUES[ea[i]].VALEVENTMPVAL;
xigrisNotify(_g("gastro_notify"), [disp,rslt,event_dt]);
//_g("rel_gastro_form").ynu[0].checked = true;
}
//Thrombolytic therapy
ea = getEvents("sep_thrombolytics_adm", SEPSISREPLY);
xigrisNotify(_g("thrombo_notify"), [disp, rslt, "Dose Given: " + event_dt]);
_g("rel_thrombo_form").ynu[0].checked = true;
}
}
…

Dirty Code
//Oral anticoagulants or...
ea = getEvents("sep_oral_anticoag_adm", SEPSISREPLY);
xigrisNotify(_g("antiglyco_notify"), [disp, rslt, "Dose Given: " + event_dt]);
_g("rel_antiglyco_form").ynu[0].checked = true;

}
}
…and going
//...glycoprotein
ea = getEvents("sep_glyco_plt_inh_adm", SEPSISREPLY);
xigrisNotify(_g("antiglyco_notify"), [disp, rslt, "Dose Given: " + event_dt]);
_g("rel_antiglyco_form").ynu[0].checked = true;
}
}
//Aspirin or...
ea = getEvents("sep_aspirin_adm", SEPSISREPLY);
xigrisNotify(_g("aspirin_notify"), [disp, rslt, "Dose Given: " + event_dt]);
//TODO - less than 24 hours
_g("rel_aspirin_form").ynu[0].checked = true;

Dirty Code
}
}
}
//...other platelet inhibitor
ea = getEvents("sep_plt_adm", SEPSISREPLY);
xigrisNotify(_g("aspirin_notify"), ["Active Order", disp]);
_g("rel_aspirin_form").ynu[0].checked = true;
}
}
//Ischemic Stroke
ea = getEvents("sep_ischemic_stk_dx", SEPSISREPLY); …and going
xigrisNotify(_g("stroke_notify"), [disp,rslt,event_dt]);
//_g("rel_stroke_form").ynu[0].checked = true;
}
//Intracranial Arteriovenous Malformation or aneurysm
ea = getEvents("sep_aneurysm_dx", SEPSISREPLY);
xigrisNotify(_g("aneurysm_notify"), [disp,rslt,event_dt]);
_g("rel_aneurysm_form").ynu[0].checked = true;
}

Dirty Code
//Chronic Severe Hepatic Disease

//...Hepatic
ea = getEvents("sep_hepatic_dis_dx", SEPSISREPLY);
xigrisNotify(_g("hepatic_notify"), [disp,rslt,event_dt]);
_g("rel_hepatic_form").ynu[0].checked = true;
}
//...ALT > 100
ea = getEvents("sep_alt_ec", SEPSISREPLY);
xigrisNotify(_g("hepatic_notify"), [disp, rslt, event_dt]);

}
} …and going
}
//...AST > 100
ea = getEvents("sep_ast_ec", SEPSISREPLY);

Dirty Code
}
}
}
//...AST
ea = getEvents("sep_bilirubin_ec", SEPSISREPLY);
}
}
}
//Pregnant or Breastfeeding
ea = getEvents("sep_pregnant_ec", SEPSISREPLY);
xigrisNotify(_g("pregnant_notify"), [disp, rslt, event_dt]);

}
_g("rel_pregnant_form").ynu[0].checked = true; …and going
}
ea = getEvents("sep_breastfeeding_ec", SEPSISREPLY);

Dirty Code
xigrisNotify(_g("pregnant_notify"), [disp, rslt, event_dt]);
_g("rel_pregnant_form").ynu[0].checked = true;
}
}
//check with handler
xigrisRelativeHandler();

}
catch (e) {
errorHandler(e, "fillXigrisRelative()");
}
}

…and going

Dirty Code
Big functions

A function should do one thing.
“One thing. Just one thing. You stick to
that and the rest don't mean sh*t.”
Curly, City Slickers

Dirty Code
High coupling

Zero Unit Tests

Dirty Code is hard to test

Zero Unit Tests

Ease of
Unit Testing

Function Size

Zero Unit Tests

Ease of
Unit Testing

Coupling

Zero Unit Tests

Ease of
Unit Testing

Number of things the
function does

Dirty Code

Zero Unit Tests

Low Test Coverage

Low Test Coverage

I relied on a little helper
who was never meant
to have so much
responsibility.

Low Test Coverage

Functional Tests
King of the Black Boxes

Low Test Coverage
Functional Testing
has its place

A-Bomb Testing, Nevada Test Site, 1955

Dirty Code

Zero Unit Tests

Low Test Coverage

Stupid Bugs

Stupid Bugs

“How in the hell
did I miss that one?”
- Me, after every defect

Conventional Development

write code


test code


What if we reversed it?
write code
test code


What if we reversed it?
test code
write code
(WTF?)

turn development on its head


“Red, Green, Refactor”


1
Write a test that fails
Red

3
Clean up code

Refactor Green

2
Make the test pass

1. Write a test that fails
1. Write one unit test
addNumber_test.js

2. Run the test and verify the failure

2. Make the test pass
1. Write just enough code to make failing test
pass. addNumber_test.js

addNumber.js

2. Run the test and verify the success

3. Clean up code

If able, clean up Code and Unit Tests

“Leave the campground cleaner than you found it.”
Boy Scouts of America

1. Write a test that fails (Round 2)
1. Write one unit test
addNumber_test.js

2. Run the test and verify the failure

2. Make the test pass (Round 2)
1. Write just enough code to make failing
test pass. addNumber_test.js

addNumber.js

2. Run the test and verify the success

3. Clean up code (Round 2)

It’s tough to clean code this simple, so
we’re done.
addNumber_test.js

addNumber.js

Clean Code

Lotsa Unit Tests

High Test Coverage

Stupid Bugs (but a whole lot less of them)

No Fear Of Breaking Anything

Clean Code

Having to test a little
code at a time forced
me to write smaller functions
with lower coupling
that did one thing.

Lotsa Unit Tests

They help me sleep at night

High Test Coverage

The code follows the tests.
It makes sense that test coverage would be high.

High Test Coverage

I no longer have to rely on the functional
testers to tell me my code works. I know
it works.

For my F5 tells me so.

No fear of breaking anything

This one’s my favorite, because it
means I can refactor mercilessly.

Every time I make a code change, I run
the tests. They tell me immediately
and loudly if I broke anything.

No fear of breaking anything

Like Patrick Bateman
in American Psycho, I
laugh maniacally while
I carve up bodies of
code.

Other Reasons that TDD Rules
Unit Tests are Documentation

Other Reasons that TDD Rules
Closes the Feedback Loop

“The act of writing a unit test is more an act of design
than of verification. It is also more an act of
documentation than of verification. The act of writing a
unit test closes a remarkable number of feedback loops,
the least of which is the one pertaining to verification
of function.”
Robert “Uncle Bob” Martin
Agile Software Development

( You know code works after
30 seconds, not 10 minutes. )

It can be quite a struggle at first.
Downright painful.

No code until you write your tests!

Test-Driven Development in JavaScript

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