How to use Test2::V0 for modern Perl testing?

Using Test2::V0 for Modern Perl Testing

Test2::V0 is a modern testing toolset for Perl, designed as a successor to the classic Test::More framework. It provides a minimalist testing interface focusing on portability, extensibility, and better diagnostics while maintaining familiar semantics. It is part of the Test2 ecosystem, which underlies most newer Perl testing modules.

Here is a concise guide on how to use Test2::V0 effectively for unit testing in modern Perl:

Key Features of Test2::V0

• Minimalist API: Functions like ok, is, is_deeply give familiar assertion tools.
• Portability: Fully compliant with TAP (Test Anything Protocol) so integrates with existing test harnesses.
• Extensibility: Modular design allows custom checks and better diagnostics.
• Minimal boilerplate: Simple import, no complicated initialization.

Installing Test2::V0

Typically, you install Test2::V0 from CPAN if not bundled with your Perl distribution (Perl 5.20+ often includes modern test2 components). Use:

cpan Test2::V0

Basic Example with Test2::V0

The following example demonstrates unit testing simple functions using Test2::V0. It shows how to write tests with ok and is, along with useful diagnostics:

use strict;
use warnings;
use Test2::V0;  # Import the main testing functions

# A simple function to test
sub add {
    my ($a, $b) = @_;
    return $a + $b;
}

# Plan the number of tests (optional in many modern frameworks)
plan tests => 4;

# Test the add function
ok(add(2, 3) == 5, '2 + 3 equals 5');
is(add(0, 0), 0, '0 + 0 equals 0');

# Test edge cases
is(add(-1, 1), 0, 'Add negative and positive to zero');
ok(add(1_000_000, 2_000_000) == 3_000_000, 'Large numbers addition');

done_testing();  # finalize (optional when plan is used)

Explanation of Perl and Test2 Concepts

• use Test2::V0; imports assert functions such as ok (generic boolean test) and is (check equality).
• plan tests => 4; defines how many tests you expect (good for early failures or skipped tests).
• ok() simply asserts a boolean expression — useful for general checks.
• is() checks if two scalar values are equal, printing diagnostics if they fail.
• The done_testing() function concludes the test run, typically used if plan is omitted.
• Sigils: $ for scalars, @ for arrays - here add returns a scalar.
• Context: Since addition returns a scalar, comparison via == works as numeric.

Common Pitfalls

• Forgetting to call plan or done_testing can lead to test harness warnings.
• Using eq vs ==: remember == is numeric comparison, eq is string.
• Test order matters: Failures early help identify errors faster.
• Test2::V0 expects tests to print TAP format, don’t add extra prints unless in diagnostics.

Summary

Test2::V0 offers a modern, compact, and extensible testing interface that fits well with contemporary Perl coding practices. It is easy to learn if you're familiar with Test::More, yet more powerful and diagnostic-friendly. Using it allows better unit testing with minimal fuss and integrates seamlessly in modern test harnesses.

Try the example above to start writing your own tests and gradually explore more features from the broader Test2 ecosystem for advanced testing needs.