经过长时间的聊天讨论，我提出以下方法进行单元测试，以及对实际代码进行轻微重组以使事情变得更容易。
我所做的更改
我已经重组了代码从模板创建错误消息的方式，以不使用Template，因为从your previous question 中可以清楚地看出这有点矫枉过正。
它现在使用sprintf 和Timeout after %s seconds 这样的简单模式。我故意在整个示例中使用%s，因为这些示例中从来没有任何类型检查，但当然可以添加它。此消息的参数作为从第二个参数开始的键/值对列表传递给构造函数。
my $e = Error->new(CONSTANT, foo => 'bar');
错误库示例
第一个参数CONSTANT 仍然来自您的错误库。我已经包含了以下简化示例。
package ErrorList;
use strict;
use warnings;
use parent 'Exporter';
use constant {
ERROR_WIFI_CABLE_TOO_SHORT => {
category => 'Layer 1',
template => 'A WiFi cable of %s meters is too short.',
context => [qw(length)],
fatal => 1,
wiki_page => 'http://example.org',
},
ERROR_CABLE_HAS_WRONG_COLOR => {
category => 'Layer 1',
template => 'You cannot connect to %s using a %s cable.',
context => [qw(router color)],
fatal => 1,
wiki_page => 'http://example.org',
},
ERROR_I_AM_A_TEAPOT => {
category => 'Layer 3',
template => 'The device at %s is a teapot.',
context => [qw(ip)],
fatal => 0,
wiki_page => 'http://example.org',
},
};
our @EXPORT = qw(
ERROR_WIFI_CABLE_TOO_SHORT
ERROR_CABLE_HAS_WRONG_COLOR
ERROR_I_AM_A_TEAPOT
);
our @EXPORT_OK = qw(ERROR_WIFI_CABLE_TOO_SHORT);
context 是一个数组引用，其中包含构造时预期的键列表。
重构（简化）的错误类
这个类包括 POD 来解释它的作用。重要的方法是构造函数message 和stringify。
package Error;
use strict;
use warnings;
=head1 NAME
Error - A handy error class
=head1 SYNOPSIS
use Error;
use ErrorList 'ERROR_WIFI_CABLE_TOO_SHORT';
my $e = Error->new(
ERROR_WIFI_CABLE_TOO_SHORT,
timeout => 30,
switch_ip => '127.0.0.1'
);
die $e->stringify;
=head1 DESCRIPTION
This class can create objects from a template and stringify them into a
log-compatible pattern. It makes sense to use it together
with L<ErrorList>.
=head1 METHODS
=head2 new($error, %args)
The constructor takes the error definition and a list of key/value pairs
with context information as its arguments.
...
=cut
sub new {
my ( $class, $error, %args ) = @_;
# initialize with the error data
my $self = $error;
# check required arguments...
foreach my $key ( @{ $self->{context} } ) {
die "$key is required" unless exists $args{$key};
# ... and take the ones we need
$self->{args}->{$key} = $args{$key}; # this could have a setter
}
return bless $self, $class;
}
=head2 category
This is the accessor for the category.
=cut
sub category {
return $_[0]->{category};
}
=head2 template
This is the accessor for the template.
=cut
sub template {
return $_[0]->{template};
}
=head2 fatal
This is the accessor for whether the error is fatal.
=cut
sub is_fatal {
return $_[0]->{fatal};
}
=head2 wiki_page
This is the accessor for the wiki_page.
=cut
sub wiki_page {
return $_[0]->{wiki_page};
}
=head2 context
This is the accessor for the context. The context is an array ref
of hash key names that are required as context arguments at construction.
=cut
sub context {
return $_[0]->{context};
}
=head2 category
This is the accessor for the args. The args are a hash ref of context
arguments that are passed in as a list at construction.
=cut
sub args {
return $_[0]->{args};
}
=head2 message
Builds the message string from the template.
=cut
sub message {
my ($self) = @_;
return sprintf $self->template,
map { $self->args->{$_} } @{ $self->context };
}
=head2 stringify
Stringifies the error to a log message, including the message,
category and wiki_page.
=cut
sub stringify {
my ($self) = @_;
return sprintf qq{%s : %s\nMore info: %s}, $self->category,
$self->message, $self->wiki_page;
}
=head1 AUTHOR
simbabque (some guy on StackOverflow)
=cut
实际的单元测试
现在要对此进行测试，区分行为和数据非常重要。 行为包括代码中定义的所有访问器，以及更有趣的子类，如new、message和stringify。
我为此示例创建的测试文件的第一部分包括这些。它创建了一个伪造的错误结构$example_error 并使用它来检查构造函数是否可以处理正确的参数、丢失或多余的参数，访问器是否返回正确的内容，以及message 和stringify 是否都创建了正确的内容。
请记住，在更改代码时（尤其是几个月后），这些测试主要是一个安全网。如果你不小心把东西改错了地方，测试就会失败。
package main; # something like 01_foo.t
use strict;
use warnings;
use Test::More;
use Test::Exception;
use LWP::Simple 'head';
subtest 'Functionality of Error' => sub {
my $example_error = {
category => 'Connection Error',
template => 'Could not ping switch %s in %s seconds.',
context => [qw(switch_ip timeout)],
fatal => 1,
wiki_page => 'http://example.org',
};
# happy case
{
my $e = Error->new(
$example_error,
timeout => 30,
switch_ip => '127.0.0.1'
);
isa_ok $e, 'Error';
can_ok $e, 'category';
is $e->category, 'Connection Error',
q{... and it returns the correct value};
can_ok $e, 'template';
is $e->template, 'Could not ping switch %s in %s seconds.',
q{... and it returns the correct values};
can_ok $e, 'context';
is_deeply $e->context, [ 'switch_ip', 'timeout' ],
q{... and it returns the correct values};
can_ok $e, 'is_fatal';
ok $e->is_fatal, q{... and it returns the correct values};
can_ok $e, 'message';
is $e->message, 'Could not ping switch 127.0.0.1 in 30 seconds.',
q{... and the message is correct};
can_ok $e, 'stringify';
is $e->stringify,
"Connection Error : Could not ping switch 127.0.0.1 in 30 seconds.\n"
. "More info: http://example.org",
q{... and stringify contains the right message};
}
# not enough arguments
throws_ok( sub { Error->new( $example_error, timeout => 1 ) },
qr/switch_ip/, q{Creating without switch_ip dies} );
# too many arguments
lives_ok(
sub {
Error->new(
$example_error,
timeout => 1,
switch_ip => 2,
foo => 3
);
},
q{Creating with too many arguments lives}
);
};
缺少一些特定的测试用例。如果您使用像 Devel::Cover 这样的度量工具，值得注意的是，完全覆盖并不意味着覆盖所有可能的情况。
测试您的错误数据质量
现在，本例中值得介绍的第二部分是 ErrorLibrary 中错误模板的正确性。以后有人可能会不小心弄混了一些东西，或者可能有一个新的占位符添加到消息中，但没有添加到上下文数组中。
下面的测试代码最好放在自己的文件中，并且仅在您完成某个功能的工作时运行，但出于说明目的，这只是在上面的代码块之后继续，因此两个第一级subtest秒。
您问题的主要部分是关于测试用例列表的。我认为这是非常重要的。您希望您的测试代码干净、易于阅读，甚至更易于维护。测试通常兼作文档，没有什么比更改代码更烦人的了，然后试图弄清楚测试是如何工作的，以便您可以更新它们。所以永远记住这一点：
测试也是生产代码！
现在让我们看一下错误的测试。
subtest 'Correctness of ErrorList' => sub {
# these test cases contain all the errors from ErrorList
my @test_cases = (
{
name => 'ERROR_WIFI_CABLE_TOO_SHORT',
args => {
length => 2,
},
message => 'A WiFi cable of 2 meters is too short.',
},
{
name => 'ERROR_CABLE_HAS_WRONG_COLOR',
args => {
router => 'foo',
color => 'red',
},
message => 'You cannot connect to foo using a red cable.',
},
{
name => 'ERROR_I_AM_A_TEAPOT',
args => {
ip => '127.0.0.1',
},
message => 'The device at 127.0.0.1 is a teapot.',
},
);
# use_ok 'ErrorList'; # only use this line if you have files!
ErrorList->import; # because we don't have a file ErrorList.pm
# in the file system
pass 'ErrorList used correctly'; # remove if you have files
foreach my $t (@test_cases) {
subtest $t->{name} => sub {
# because we need to use a variable to get to a constant
no strict 'refs';
# create the Error object from the test data
# will also fail if the name was not exported by ErrorList
my $e;
lives_ok(
sub { $e = Error->new( &{ $t->{name} }, %{ $t->{args} } ) },
q{Error can be created} );
# and see if it has the right values
is $e->message, $t->{message},
q{... and the error message is correct};
# use LWP::Simple to check if the wiki page link is not broken
ok head( $e->wiki_page ), q{... and the wiki page is reachable};
};
}
};
done_testing;
它基本上有一组测试用例，每个由 ErrorLibrary 导出的可能错误常量都有一个用例。它具有名称，用于加载正确的错误并识别 TAP 输出中的测试用例、运行测试所需的参数以及预期的最终输出。我只包含 message 以保持简短。
如果错误模板名称在 ErrorLibrary 中被修改（或删除）而不更改文本，则对象实例化周围的 lives_ok 将失败，因为该名称未导出。这是一个不错的加分项。
但是，如果在没有测试用例的情况下添加了新错误，它不会捕获。一种方法是查看 main 命名空间中的符号表，但这对于此答案的范围来说有点太高级了。
它还可以使用LWP::Simple 向每个wiki URL 发出HEAD HTTP 请求，以查看它们是否可以访问。这也有一个很好的好处，如果您在构建时运行它，它的作用有点像监控工具。
将所有内容整合在一起
最后，这里是 TAP 输出，当没有prove 运行时。
# Subtest: Functionality of Error
ok 1 - An object of class 'Error' isa 'Error'
ok 2 - Error->can('category')
ok 3 - ... and it returns the correct value
ok 4 - Error->can('template')
ok 5 - ... and it returns the correct values
ok 6 - Error->can('context')
ok 7 - ... and it returns the correct values
ok 8 - Error->can('is_fatal')
ok 9 - ... and it returns the correct values
ok 10 - Error->can('message')
ok 11 - ... and the message is correct
ok 12 - Error->can('stringify')
ok 13 - ... and stringify contains the right message
ok 14 - Creating without switch_ip dies
ok 15 - Creating with too many arguments lives
1..15
ok 1 - Functionality of Error
# Subtest: Correctness of ErrorList
ok 1 - ErrorList used correctly
# Subtest: ERROR_WIFI_CABLE_TOO_SHORT
ok 1 - Error can be created
ok 2 - ... and the error message is correct
ok 3 - ... and the wiki page is reachable
1..3
ok 2 - ERROR_WIFI_CABLE_TOO_SHORT
# Subtest: ERROR_CABLE_HAS_WRONG_COLOR
ok 1 - Error can be created
ok 2 - ... and the error message is correct
ok 3 - ... and the wiki page is reachable
1..3
ok 3 - ERROR_CABLE_HAS_WRONG_COLOR
# Subtest: ERROR_I_AM_A_TEAPOT
ok 1 - Error can be created
ok 2 - ... and the error message is correct
ok 3 - ... and the wiki page is reachable
1..3
ok 4 - ERROR_I_AM_A_TEAPOT
1..4
ok 2 - Correctness of ErrorList
1..2