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```{index} single: Test2::Compare::Base
```

# Test2::Compare::Base

Base class for comparison classes.

## DESCRIPTION

All comparison classes for Test2::Compare should inherit from this base class.

## SYNOPSIS

```perl
package Test2::Compare::MyCheck;
use strict;
use warnings;

use base 'Test2::Compare::Base';
use Test2::Util::HashBase qw/stuff/;

sub name { 'STUFF' }

sub operator {
    my $self = shift;
    my ($got) = @_;
    return 'eq';
}

sub verify {
    my $self = shift;
    my $params = @_;

    # Always check if $got exists! This method must return false if no
    # value at all was received.
    return 0 unless $params{exists};

    my $got = $params{got};

    # Returns true if both values match. This includes undef, 0, and other
    # false-y values!
    return $got eq $self->stuff;
}
```

## METHODS

Some of these must be overridden, others can be.

- $dclass = $check->delta\_class

    Returns the delta subclass that should be used. By default
    [Test2::Compare::Delta](Delta.md) is used.

- @deltas = $check->deltas(id => $id, exists => $bool, got => $got, convert => \\&convert, seen => \\%seen)

    Should return child deltas.

- @lines = $check->got\_lines($got)

    This is your chance to provide line numbers for errors in the `$got`
    structure.

- $op = $check->operator()
- $op = $check->operator($got)

    Returns the operator that was used to compare the check with the received data
    in `$got`. If there was no value for got then there will be no arguments,
    undef will only be an argument if undef was seen in `$got`. This is how you
    can tell the difference between a missing value and an undefined one.

- $bool = $check->verify(id => $id, exists => $bool, got => $got, convert => \\&convert, seen => \\%seen)

    Return true if there is a shallow match, that is both items are arrayrefs, both
    items are the same string or same number, etc. This should not recurse, as deep
    checks are done in `$check->deltas()`.

- $name = $check->name

    Get the name of the check.

- $display = $check->render

    What should be displayed in a table for this check, usually the name or value.

- $delta = $check->run(id => $id, exists => $bool, got => $got, convert => \\&convert, seen => \\%seen)

    This is where the checking is done, first a shallow check using
    `$check->verify`, then checking `$check->deltas()`. `\%seen` is used
    to prevent cycles.

## SOURCE

The source code repository for Test2-Suite can be found at
`https://github.com/Test-More/test-more/`.

## MAINTAINERS

- Chad Granum <exodist@cpan.org>

## AUTHORS

- Chad Granum <exodist@cpan.org>

## COPYRIGHT

Copyright Chad Granum <exodist@cpan.org>.

This program is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

See `http://dev.perl.org/licenses/`