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Slides for a talk I gave to my team at work, in order to convince them that TDD is one of the best things they could do to improve their code.
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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.
Stupid Bugs
Low Test Coverage
Dirty Code
Fear Of Breaking Anything
Zero Unit Tests
Dirty Code
function fillXigrisRelative(){ try { var at = _g("relativeTable"); //var docfrag = document.createDocumentFragment(); //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); 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 > 40) { _g("rel_inrptt_form").ynu[0].checked = true; } } } …
Dirty Code
Big functions
//Platelet Count ea = getEvents("sep_plt_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("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); for (i = 0; i < ea.length; i++) { 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); 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("thrombo_notify"), [disp, rslt, "Dose Given: " + event_dt]); _g("rel_thrombo_form").ynu[0].checked = true; } } …
…that keep going
Dirty Code
//Oral anticoagulants or... ea = getEvents("sep_oral_anticoag_adm", 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("antiglyco_notify"), [disp, rslt, "Dose Given: " + event_dt]); _g("rel_antiglyco_form").ynu[0].checked = true; } } //...glycoprotein ea = getEvents("sep_glyco_plt_inh_adm", 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("antiglyco_notify"), [disp, rslt, "Dose Given: " + event_dt]); _g("rel_antiglyco_form").ynu[0].checked = true; } } //Aspirin or... ea = getEvents("sep_aspirin_adm", 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("aspirin_notify"), [disp, rslt, "Dose Given: " + event_dt]); //TODO - less than 24 hours if (SEPSISREPLY.VALUES[ea[i]].EVENTS[j].RSLTVAL > 650) { _g("rel_aspirin_form").ynu[0].checked = true;
…and going
Dirty Code
} } } //...other platelet inhibitor ea = getEvents("sep_plt_adm", 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("aspirin_notify"), ["Active Order", disp]); _g("rel_aspirin_form").ynu[0].checked = true; } } //Ischemic Stroke ea = getEvents("sep_ischemic_stk_dx", SEPSISREPLY); for (i = 0; i < ea.length; i++) { disp = SEPSISREPLY.VALUES[ea[i]].VALEVENTFTX; rslt = SEPSISREPLY.VALUES[ea[i]].VALEVENTNOMDISP; event_dt = SEPSISREPLY.VALUES[ea[i]].VALEVENTMPVAL; 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); for (i = 0; i < ea.length; i++) { disp = SEPSISREPLY.VALUES[ea[i]].VALEVENTFTX; rslt = SEPSISREPLY.VALUES[ea[i]].VALEVENTNOMDISP; event_dt = SEPSISREPLY.VALUES[ea[i]].VALEVENTMPVAL; xigrisNotify(_g("aneurysm_notify"), [disp,rslt,event_dt]); _g("rel_aneurysm_form").ynu[0].checked = true; }
…and going
Dirty Code
//Chronic Severe Hepatic Disease //...Hepatic ea = getEvents("sep_hepatic_dis_dx", SEPSISREPLY); for (i = 0; i < ea.length; i++) { disp = SEPSISREPLY.VALUES[ea[i]].VALEVENTFTX; rslt = SEPSISREPLY.VALUES[ea[i]].VALEVENTNOMDISP; event_dt = SEPSISREPLY.VALUES[ea[i]].VALEVENTMPVAL; xigrisNotify(_g("hepatic_notify"), [disp,rslt,event_dt]); _g("rel_hepatic_form").ynu[0].checked = true; } //...ALT > 100 ea = getEvents("sep_alt_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("hepatic_notify"), [disp, rslt, event_dt]); if (SEPSISREPLY.VALUES[ea[i]].EVENTS[j].RSLTVAL > 100) { _g("rel_hepatic_form").ynu[0].checked = true; } } } //...AST > 100 ea = getEvents("sep_ast_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("hepatic_notify"), [disp, rslt, event_dt]);
…and going
Dirty Code
if (SEPSISREPLY.VALUES[ea[i]].EVENTS[j].RSLTVAL > 100) { _g("rel_hepatic_form").ynu[0].checked = true; } } } //...AST ea = getEvents("sep_bilirubin_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("hepatic_notify"), [disp, rslt, event_dt]); if (SEPSISREPLY.VALUES[ea[i]].EVENTS[j].RSLTVAL > 2) { _g("rel_hepatic_form").ynu[0].checked = true; } } } //Pregnant or Breastfeeding ea = getEvents("sep_pregnant_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("pregnant_notify"), [disp, rslt, event_dt]); _g("rel_pregnant_form").ynu[0].checked = true; } } ea = getEvents("sep_breastfeeding_ec", SEPSISREPLY); for (i = 0; i < ea.length; i++) {
…and going
Dirty Code
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("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
Dirty Code
A function should do one thing.
Big functions
“One thing. Just one thing. You stick to
that and the rest don't mean sh*t.”
Curly, City Slickers
High coupling
Dirty Code
Dirty Code
Zero Unit Tests
Zero Unit Tests
Dirty Code is hard to test
Ease of
Unit Testing
Function Size
Zero Unit Tests
Zero Unit Tests
Coupling
Ease of
Unit Testing
Zero Unit Tests
Number of things the
function does
Ease of
Unit Testing
Low Test Coverage
Dirty Code
Zero Unit Tests
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
Stupid Bugs
Low Test Coverage
Dirty Code
Zero Unit Tests
Stupid Bugs
“How in the hell
did I miss that one?” - Me, after every defect
Stupid Bugs
Low Test Coverage
Dirty Code
Fear Of Breaking Anything
Zero Unit Tests
Fear of Breaking Anything
code write
Conventional Development
Conventional Development
code test
Conventional Development
What if we reversed it?
code write code test
Conventional Development
What if we reversed it?
code test code write
(WTF?)
Test-Driven Development turn development on its head
Test-Driven Development
“Red, Green, Refactor”
Red
Green Refactor
Test-Driven Development
Write a test that fails
Make the test pass
1
2
Clean up code 3
a (very) trivial example
1. Write a test that fails
1. Write one unit test
2. Run the test and verify the failure
addNumber_test.js
2. Make the test pass
1. Write just enough code to make failing test
pass.
2. Run the test and verify the success
addNumber_test.js
addNumber.js
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
1. Write one unit test
2. Run the test and verify the failure
addNumber_test.js
(Round 2)
2. Make the test pass
1. Write just enough code to make failing
test pass.
2. Run the test and verify the success
addNumber.js
addNumber_test.js
(Round 2)
3. Clean up code
It’s tough to clean code this simple, so
we’re done.
addNumber.js
addNumber_test.js
(Round 2)
Stupid Bugs
Low Test Coverage
Dirty Code
Fear Of Breaking Anything
Zero Unit Tests
Stupid Bugs (but a whole lot less of them)
High Test Coverage
Clean Code
No Fear Of Breaking Anything
Lotsa Unit Tests
Clean Code
smaller functions
Having to test a little
code at a time forced
me to write
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
“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
Closes the Feedback Loop
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!
Not a silver bullet
Questions?
