unit testing you ain’t doing it, and you should david cantrell...
TRANSCRIPT
Unit Testing
You ain’t doing it, and you should
David Cantrell [email protected]
Chief Plumber, UK2 Ltd
Unit Testing
You ain’t doing it, and you should
David Cantrell [email protected]
Chief Plumber, UK2 Ltd
12:20 <@dc> ees me, ees mario!12:21 <@ned> dc is promoted to chief plumber, in charge of princess rescue and mushroom eating
Boss
This is your code
This is your code
This is your code
Let’s run a test
GET /foo/bar/baz
Let’s run a test
GET /foo/bar/baz
Let’s run a test
GET /foo/bar/baz
Let’s run a test
GET /foo/bar/baz
Let’s run a test
GET /foo/bar/baz
Let’s run a test
GET /foo/bar/baz
Let’s run a test
GET /foo/bar/baz
Let’s run a test
GET /foo/bar/baz
Let’s run a test
GET /foo/bar/baz
Let’s run a test
GET /foo/bar/baz
not ok 43572 GET /customer/94/invoice got right data
Where was that test failure?
Why do we test?
Why do we test?
•Testing new codedid I get this new feature right?
Why do we test?
•Testing new codedid I get this new feature right?
•Regression testingdid I break any existing code?
Why do we test?
•Testing new codedid I get this new feature right?
•Regression testingdid I break any existing code?
what did I break?
Why do we test?
•Testing new codedid I get this new feature right?
•Regression testingdid I break any existing code?
what did I break?
where?
The solution (sort of)
The solution (sort of)
The solution (sort of)
The solution (sort of)
and so on ad infinitum et tedium
That solution sucks
Great, you just tested most ofyour code multiple times.
That solution sucks
Great, you just tested most ofyour code multiple times.
Your tests took two hours.
That solution sucks
Great, you just tested most ofyour code multiple times.
Your tests took two hours.
And again when you think you fixed them.
But that wasn’t unit testing
This is unit testing
This is unit testing
This is unit testing
This is unit testing
Repeat ad infinitum et tedium
This is unit testing
You just tested all ofyour code once!
Your tests took twenty minutes!
That’s the end of the theory
Any questions?
Let’s look at some code
Let’s look at some code
(it doesn’t do much)
Let’s look at some code
End to end testspackage Dancer::Example::Calculator::Add;
use strict;use warnings;use WWW::Google::Calculator;
sub get { my $class = shift; my @numbers = @_; die("illegal arguments") if( grep { $_ !~ /^-?\d+(\.\d+)?$/ } @numbers ); my $result = WWW::Google::Calculator-> new()->calc("$numbers[0] + $numbers[1]"); $result =~ s/.*= //; return $result;}
1;
use Dancer::Test;
...
response_status_is( [ GET => '/add/2/lemon'], 500, "GET /add/2/lemon - HTTP status is correct" ); response_status_is( [ GET => '/add/2/4'], 200, "GET /add/2/4 - HTTP status is correct" ); response_content_is( [ GET => '/add/2/4'], '6', "GET /add/2/4 - content is correct" );
End to end testspackage Dancer::Example::Calculator::Add;
use strict;use warnings;use WWW::Google::Calculator;
sub get { my $class = shift; my @numbers = @_; die("illegal arguments") if( grep { $_ !~ /^-?\d+(\.\d+)?$/ } @numbers ); my $result = WWW::Google::Calculator-> new()->calc("$numbers[0] + $numbers[1]"); $result =~ s/.*= //; return $result;}
1;
use Dancer::Test;
...
SKIP: { skip "google isn't responding or its interface has changed", 3 unless(do { my $r = eval { WWW::Google::Calculator->new()->calc('1+1') }; defined($r) && $r eq '1 + 1 = 2'; });
response_status_is( [ GET => '/add/2/lemon'], 500, "GET /add/2/lemon - HTTP status is correct" ); response_status_is( [ GET => '/add/2/4'], 200, "GET /add/2/4 - HTTP status is correct" ); response_content_is( [ GET => '/add/2/4'], '6', "GET /add/2/4 - content is correct" );}
End to end testspackage Dancer::Example::Calculator::Add;
use strict;use warnings;use WWW::Google::Calculator;
sub get { my $class = shift; my @numbers = @_; die("illegal arguments") if( grep { $_ !~ /^-?\d+(\.\d+)?$/ } @numbers ); my $result = WWW::Google::Calculator-> new()->calc("$numbers[0] + $numbers[1]"); $result =~ s/.*= //; return $result;}
1;
use Dancer::Test;
...
SKIP: { skip "google isn't responding or its interface has changed", 3 unless(do { my $r = eval { WWW::Google::Calculator->new()->calc('1+1') }; defined($r) && $r eq '1 + 1 = 2'; });
response_status_is( [ GET => '/add/2/lemon'], 500, "GET /add/2/lemon - HTTP status is correct" ); response_status_is( [ GET => '/add/2/4'], 200, "GET /add/2/4 - HTTP status is correct" ); response_content_is( [ GET => '/add/2/4'], '6', "GET /add/2/4 - content is correct" );}
$ time PERL5LIB=lib prove t/end-to-end.t t/end-to-end.t .. ok All tests successful.Files=1, Tests=3, 8 wallclock secs ...
Get rid of the front-end layerpackage Dancer::Example::Calculator::Add;
use strict;use warnings;use WWW::Google::Calculator;
sub get { my $class = shift; my @numbers = @_; die("illegal arguments") if( grep { $_ !~ /^-?\d+(\.\d+)?$/ } @numbers ); my $result = WWW::Google::Calculator->new()->calc("$numbers[0] + $numbers[1]"); $result =~ s/.*= //; return $result;}
1;throws_ok( sub { Dancer::Example::Calculator::Add->get(1, 'lemons') }, qr/illegal arguments/, "catches non-numeric args");...
is(Dancer::Example::Calculator::Add->get(2, 3), 5, "Add->get() works for a simple case");
# Test that the error thrown above doesn't accidentally catch# some legit datais(Dancer::Example::Calculator::Add->get(-4, 2), -2, "works for -ves too");is(Dancer::Example::Calculator::Add->get(0.2, 1), 1.2, "and decimals");is(Dancer::Example::Calculator::Add->get(1, -2.2), -1.2, "and -ve decimals");
Prepare to mock the call to Googlepackage Dancer::Example::Calculator::Add;
use strict;use warnings;use Class::Mockable _google_calculator => 'Dancer::Example::Calculator::Utils::GoogleInterface';use Dancer::Example::Calculator::Utils::GoogleInterface;
sub get { my $class = shift; my @numbers = @_; die("illegal arguments") if( grep { $_ !~ /^-?\d+(\.\d+)?$/ } @numbers ); my $result = _google_calculator->calc("$numbers[0] + $numbers[1]”);
return $result;}
1;throws_ok( sub { Dancer::Example::Calculator::Add->get(1, 'lemons') }, qr/illegal arguments/, "catches non-numeric args");...
is(Dancer::Example::Calculator::Add->get(2, 3), 5, "Add->get() works for a simple case");
# Test that the error thrown above doesn't accidentally catch# some legit datais(Dancer::Example::Calculator::Add->get(-4, 2), -2, "works for -ves too");is(Dancer::Example::Calculator::Add->get(0.2, 1), 1.2, "and decimals");is(Dancer::Example::Calculator::Add->get(1, -2.2), -1.2, "and -ve decimals");
Prepare to mock the call to Googlepackage Dancer::Example::Calculator::Add;
use strict;use warnings;use Class::Mockable _google_calculator => 'Dancer::Example::Calculator::Utils::GoogleInterface';use Dancer::Example::Calculator::Utils::GoogleInterface;
sub get { my $class = shift; my @numbers = @_; die("illegal arguments") if( grep { $_ !~ /^-?\d+(\.\d+)?$/ } @numbers ); my $result = _google_calculator->calc("$numbers[0] + $numbers[1]”);
return $result;}
1;
package Dancer::Example::Calculator::Utils::GoogleInterface;
use strict;use warnings;
use WWW::Google::Calculator;
sub calc { my $class = shift; my $sum = shift; (my $result = WWW::Google::Calculator->new()->calc($sum)) =~ s/.*= //; return $result;}
1;
Mock the call to Google
throws_ok( sub { Dancer::Example::Calculator::Add->get(1, 'lemons') }, qr/illegal arguments/, "catches non-numeric args");...
is(Dancer::Example::Calculator::Add->get(2, 3), 5, "Add->get() works for a simple case");
# Test that the error thrown above doesn't accidentally catch# some legit data.is(Dancer::Example::Calculator::Add->get(-4, 2), -2, "works for -ves too");is(Dancer::Example::Calculator::Add->get(0.2, 1), 1.2, "and decimals");is(Dancer::Example::Calculator::Add->get(1, -2.2), -1.2, "and -ve decimals");
Mock the call to Google
throws_ok( sub { Dancer::Example::Calculator::Add->get(1, 'lemons') }, qr/illegal arguments/, "catches non-numeric args");...
is(Dancer::Example::Calculator::Add->get(2, 3), 5, "Add->get() works for a simple case");
# Test that the error thrown above doesn't accidentally catch# some legit data. The bogus results prove we’re mocking.is(Dancer::Example::Calculator::Add->get(-4, 2), 7, "works for -ves too");is(Dancer::Example::Calculator::Add->get(0.2, 1), 11, "and decimals");is(Dancer::Example::Calculator::Add->get(1, -2.2), -94, "and -ve decimals");
Mock the call to Googleuse Class::Mock::Generic::InterfaceTester;Dancer::Example::Calculator::Add->_google_calculator( Class::Mock::Generic::InterfaceTester->new([ { method => 'calc', input => [ '2 + 3' ], output => 5 }, { method => 'calc', input => [ '-4 + 2' ], output => 7 }, { method => 'calc', input => [ '0.2 + 1' ], output => 11 }, { method => 'calc’, input => [ '1 + -2.2' ], output => -94 }, ]) );
throws_ok( sub { Dancer::Example::Calculator::Add->get(1, 'lemons') }, qr/illegal arguments/, "catches non-numeric args");...
is(Dancer::Example::Calculator::Add->get(2, 3), 5, "Add->get() works for a simple case");
# Test that the error thrown above doesn't accidentally catch# some legit data. The bogus results prove we’re mocking.is(Dancer::Example::Calculator::Add->get(-4, 2), 7, "works for -ves too");is(Dancer::Example::Calculator::Add->get(0.2, 1), 11, "and decimals");is(Dancer::Example::Calculator::Add->get(1, -2.2), -94, "and -ve decimals");
Mock the call to Googleuse Class::Mock::Generic::InterfaceTester;Dancer::Example::Calculator::Add->_google_calculator( Class::Mock::Generic::InterfaceTester->new([ { method => 'calc', input => [ '2 + 3' ], output => 5 }, { method => 'calc', input => [ '-4 + 2' ], output => 7 }, { method => 'calc', input => [ '0.2 + 1' ], output => 11 }, { method => 'calc’, input => [ '1 + -2.2' ], output => -94 }, ]) );
throws_ok( sub { Dancer::Example::Calculator::Add->get(1, 'lemons') }, qr/illegal arguments/, "catches non-numeric args");...
is(Dancer::Example::Calculator::Add->get(2, 3), 5, "Add->get() works for a simple case");
# Test that the error thrown above doesn't accidentally catch# some legit data. The bogus results prove we’re mocking.is(Dancer::Example::Calculator::Add->get(-4, 2), 7, "works for -ves too");is(Dancer::Example::Calculator::Add->get(0.2, 1), 11, "and decimals");is(Dancer::Example::Calculator::Add->get(1, -2.2), -94, "and -ve decimals");
$ time PERL5LIB=lib prove t/add.t t/add.t .. ok All tests successful.Files=1, Tests=8, 0 wallclock secs ...
Any questions?
Any questions?Isn’t mocking dangerous? Surely you need to test your whole application?
Any questions?Isn’t mocking dangerous? Surely you need to test your whole application?
Yes. You still need some end-to-end tests.
Any questions?Isn’t mocking dangerous? Surely you need to test your whole application?
Yes. You still need some end-to-end tests.
Mocking everything seems like an awful lot of work.
Any questions?Isn’t mocking dangerous? Surely you need to test your whole application?
Yes. You still need some end-to-end tests.
Mocking everything seems like an awful lot of work.
That’s not a question.
Any questions?Isn’t mocking dangerous? Surely you need to test your whole application?
Yes. You still need some end-to-end tests.
Mocking everything seems like an awful lot of work.
Be pragmatic about what you mock, and think aboutwhy you mock. At least make your dependencies andinterfaces mockable, even if you don’t actually doany mocking straight away.
Any questions?Isn’t mocking dangerous? Surely you need to test your whole application?
Yes. You still need some end-to-end tests.
Mocking everything seems like an awful lot of work.
Be pragmatic about what you mock, and think aboutwhy you mock. At least make your dependencies andinterfaces mockable, even if you don’t actually doany mocking straight away.
Have you seen the new Doctor Who?
Any questions?Isn’t mocking dangerous? Surely you need to test your whole application?
Yes. You still need some end-to-end tests.
Mocking everything seems like an awful lot of work.
Be pragmatic about what you mock, and think aboutwhy you mock. At least make your dependencies andinterfaces mockable, even if you don’t actually doany mocking straight away.
Have you seen the new Doctor Who?
No. Doctor Who is rubbish.
Resources
Class::Mockable
The Art of Unit Testing, by Roy Osherove pub: Manning ISBN: 1933988274