Using global constants turned not to be a good idea, some more tests.

cpanfile

@@ -12,3 +12,4 @@ requires 'DateTime';
 requires 'DateTime::Format::ISO8601';
 requires 'Test::Most';
 requires 'Test::MockModule';
+requires 'Test::Warnings';

lib/BeastBB.pm

@@ -13,10 +13,8 @@ use Mojo::File;
 use Const::Fast;
 use Params::ValidationCompiler 'validation_for';
 
-use BeastBB::Constants (
-    '$HOME_DIR', '$HOME_CONFIG_DIR', '$CONFIG_FILE',
-    '$SECRET_DEFAULT_SIZE'
-);
+use BeastBB::Constants ( 'HomeConfigDir', 'ConfigFile',
+    'SecretDefaultSize' );
 use BeastBB::ConfigWriter;
 use BeastBB::Database;
 use BeastBB::Response;
@@ -51,9 +49,10 @@ sub PrepareHelpers {
     );
     $self->helper(
         logged_user => sub {
-            my $self     = shift;
-            my $session  = $self->session;
-            return BeastBB::Response->new( is_error => 1, error_message => 'User is not logged in.');
+            my $self    = shift;
+            my $session = $self->session;
+            return BeastBB::Response->new( is_error => 1,
+                error_message => 'User is not logged in.' );
             my $username = $session->{username};
         }
     );
@@ -107,13 +106,13 @@ sub PrepareInstallationRoutes {
 
 sub PrepareConfig {
     my $self = shift;
-    $HOME_CONFIG_DIR->make_path if !-e $HOME_CONFIG_DIR;
-    if ( !-e $CONFIG_FILE ) {
+    HomeConfigDir()->make_path if !-e HomeConfigDir();
+    if ( !-e ConfigFile() ) {
         my $config_writer =
-          BeastBB::ConfigWriter->new( config_file => $CONFIG_FILE );
+          BeastBB::ConfigWriter->new( config_file => ConfigFile() );
         $config_writer->PopulateExampleConfigFile(
-            secret_size => $SECRET_DEFAULT_SIZE );
+            secret_size => SecretDefaultSize() );
     }
-    $self->plugin( Config => file => $CONFIG_FILE->to_string );
+    $self->plugin( Config => file => ConfigFile()->to_string );
 }
 1;

lib/BeastBB/Constants.pm

@@ -9,10 +9,18 @@ use Exporter qw/import/;
 use Const::Fast;
 
 our @EXPORT_OK =
-  ( '$HOME_DIR', '$HOME_CONFIG_DIR', '$CONFIG_FILE', '$SECRET_DEFAULT_SIZE' );
+  ( '&HomeDir', '&HomeConfigDir', '&ConfigFile', '&SecretDefaultSize' );
 
-const our $HOME_DIR            => Mojo::File->new( $ENV{HOME} );
-const our $HOME_CONFIG_DIR     => $HOME_DIR->child( '.config', 'beastbb' );
-const our $CONFIG_FILE         => $HOME_CONFIG_DIR->child('BeastBB.conf');
-const our $SECRET_DEFAULT_SIZE => 64;
+sub HomeDir {
+    return Mojo::File->new( $ENV{HOME} );
+}
+sub HomeConfigDir {
+    return HomeDir->child( '.config', 'beastbb' );
+}
+sub ConfigFile {
+    return HomeConfigDir->child('BeastBB.conf');
+}
+sub SecretDefaultSize {
+    return 64;
+}
 1;

lib/BeastBB/Controller/Install.pm

@@ -14,7 +14,7 @@ use Types::Standard qw/Str HashRef/;
 use BeastBB::Database;
 use BeastBB::ConfigWriter;
 use BeastBB::DAO::UserManager;
-use BeastBB::Constants ('$CONFIG_FILE');
+use BeastBB::Constants ('ConfigFile');
 
 sub welcome {
     my $self  = shift;
@@ -64,7 +64,7 @@ sub install_database {
     $self->config->{db} = $config_db;
     local $Data::Dumper::Terse = 1;
     my $config_writer =
-      BeastBB::ConfigWriter->new( config_file => $CONFIG_FILE );
+      BeastBB::ConfigWriter->new( config_file => ConfigFile() );
     $config_writer->WriteToConfigFile(
         content => Data::Dumper::Dumper $self->config );
     $self->redirect_to('/');
@@ -100,7 +100,7 @@ sub admin_user_create {
     }
 
     my $config_writer =
-      BeastBB::ConfigWriter->new( config_file => $CONFIG_FILE );
+      BeastBB::ConfigWriter->new( config_file => ConfigFile );
     $config->{finished_install} = 1;
     local $Data::Dumper::Terse = 1;
     $config_writer->WriteToConfigFile(

t/00-beastbb.t

@@ -0,0 +1,37 @@
+use 5.32.1;
+
+use Test::Most tests => 4;
+
+use strict;
+use warnings;
+
+use Path::Tiny;
+use Test::MockModule;
+
+use Data::Dumper;
+
+use BeastBB::Constants qw/ConfigFile/;
+
+{
+    use_ok 'BeastBB';
+}
+
+{
+    # GIVEN
+    my $path_tiny_tempdir_home = Path::Tiny->tempdir;
+    my $mock_module_constants  = Test::MockModule->new('BeastBB::Constants');
+    $mock_module_constants->mock(
+        HomeDir => sub {
+            return Mojo::File->new($path_tiny_tempdir_home . '');
+        }
+    );
+    my $beastbb = BeastBB->new;
+    # WHEN
+    $beastbb->PrepareConfig;
+    # THEN
+    my $config = eval ConfigFile->slurp;
+    ok length $config->{secrets}[0] == 128, 'The config has been successfully created';
+    is_deeply $beastbb->config, $config, 'The populated in program config matches the content of the file.';
+    $config->{secrets} = [];
+    is_deeply $config, { secrets => [] }, 'The config matches the expected structure.';
+}

t/01-response.t

@@ -0,0 +1,36 @@
+use 5.32.1;
+
+use Test::Most tests => 4;
+use Test::Warnings ':all';
+
+use strict;
+use warnings;
+
+{
+    use_ok 'BeastBB::Response';
+}
+
+{
+    like(
+        warning {
+            BeastBB::Response->new(
+                is_error => 1,
+                content  => 'example_content', error_message => 'example_error'
+            )
+        },
+        qr/Error should not have content/,
+        'BeastBB::Response warns on construction if is_error is true and content is passed.'
+    );
+}
+
+{
+    like(
+        warning {
+            BeastBB::Response->new(
+                is_error => 1,
+            )
+        },
+        qr/You should pass a error message on error\./,
+        'BeastBB::Response warns on construction if is_error is true and error message is not passed.'
+    );
+}