This document provides an introduction to unit testing in Perl. It discusses the goals of unit testing, benefits like finding problems earlier and facilitating code changes. While tests cannot prove software is completely correct, they do increase programmer confidence. The document demonstrates how to write simple tests in Perl using Test::Simple and Test::More, which provide functions like ok(), is(), and isnt() to test conditions. It also covers some common conventions for organizing test files and folders.

1. Perl Testing 101
Craig Treptow, August, 2013

2. Unit Tests
Goal
Isolate each part of a program and show that
the individual parts are correct.

3. Unit Tests
Benefits
● Find problems earlier
● Facilitate code changes
○ Help ensure changes did not affect other behavior
● Makes integration testing easier
● Code becomes “self documenting”
○ Just look at the tests

4. Unit Tests
Reality
● They do not “prove” software is correct
● They can be
○ wrong
○ hard to set up
● They do
○ increase programmer confidence
○ need to be treated like “real code”

5. Perl Testing
What is test code?
It’s just Perl code:
#!/usr/bin/perl -w
print "1..1n";
print 1 + 1 == 2 ? "ok 1n" : "not ok 1n";
Since 1 + 1 is 2, it prints:
1..1
ok 1

6. Perl Testing
1..1
ok 1
This says:
● I’m going to run 1 test
● The test passed

7. Perl Testing
Writing that kind of code would get tedious.
So, start with Test::Simple:
#!/usr/bin/perl -w
use Test::Simple tests => 1;
ok( 1 + 1 == 2 );
That runs the same test as before.

8. Perl Testing
Want more tests?
#!/usr/bin/perl -w
use Test::Simple tests => 2;
ok( 1 + 1 == 2 );
ok( 2 + 2 == 5 );
Run the test:
perl simple.t
Produces:
1..2
ok 1
not ok 2
#
Failed test (test.pl at line 5)
# Looks like you failed 1 tests of 2.

9. Perl Testing
Before we go on:
a few conventions
● Test files are kept in folders called ‘t’
● Test files are named <something>.t
○ 00-<test prerequisites>.t
○ 10-<module name>.t
○ 20-<module name>.t
There aren’t “rules”, it’s Perl!!

10. Perl Testing
Test::Simple
● Only provides ok()
● Can be awkward
○ Can’t tell what you got for a result
○ Only True/False (ok/not ok)
There is hope...

11. Perl Testing
Test::More
● ok(), is(), isnt()
● like(), unlike()
● cmp_ok(), can_ok(), isa_ok()
● use_ok(), require_ok()
● is_deeply()
● eq_array(), eq_hash(), eq_set