Add test for previously discovered bug.

Build.PL

@@ -22,5 +22,10 @@ my $build = Module::Build->new(
         'Pango'                       => 0,
         'Crypt::URandom'              => 0,
     },
+    test_requires => {
+        'Test::MockModule' => 0,
+        'Test::Most'       => 0,
+        'Test::MockObject' => 0,
+    }
 );
 $build->create_build_script;

lib/JapaChar.pm

@@ -14,7 +14,7 @@ use YAML::PP;
 use JapaChar::DB;
 use JapaChar::Characters;
 use Pango;
-use Crypt::URandom qw( urandom );
+use JapaChar::Random;
 
 use Glib::IO;
 
@@ -58,9 +58,7 @@ sub _new_challenge($self, $window, $type = undef) {
         $self->_create_main_menu($window);
         return;
     }
-    my $rng = urandom(4);
-    $rng = unpack 'L', $rng;
-    $rng = ($rng % 100) + 1;
+    my $rng = JapaChar::Random->new->get(1, 100);
     if ($rng > 50) {
         $self->_new_challenge_romanji($window, $type);
         return;

lib/JapaChar/Characters.pm

@@ -10,6 +10,8 @@ use Path::Tiny;
 use JSON;
 use Data::Dumper;
 
+use JapaChar::Random;
+
 my $option_populated = 'populated_basic_characters';
 require JapaChar::DB;
 require JapaChar::Schema;
@@ -68,7 +70,7 @@ sub get_4_incorrect_answers( $self, $char ) {
     return \@bad_answers;
 }
 
-sub next_review_char( $self, $type = undef ) {
+sub _next_review_char( $self, $type = undef ) {
     my $basic_character_resultset =
       JapaChar::Schema->Schema->resultset('BasicCharacter');
     my @chars = $basic_character_resultset->search(
@@ -90,22 +92,23 @@ sub next_review_char( $self, $type = undef ) {
 }
 
 sub next_char( $self, $type = undef ) {
-    my $next_review   = $self->next_review_char($type);
-    my $next_learning = $self->next_learning_char($type);
+    my $next_review   = $self->_next_review_char($type);
+    my $next_learning = $self->_next_learning_char($type);
     if ( !defined $next_review ) {
         return $next_learning;
     }
     if ( !defined $next_learning) {
         return $next_review;
     }
-    my $rng = int( rand(100) ) + 1;
+    my $rng = JapaChar::Random->new->get(1, 100);
     if ( $rng > 20 ) {
         return $next_learning;
     }
     return $next_review;
 }
 
-sub next_learning_char( $self, $type = undef ) {
+
+sub _next_learning_char( $self, $type = undef ) {
     $self->populate_basic_characters;
     my $basic_character_resultset =
       JapaChar::Schema->Schema->resultset('BasicCharacter');

lib/JapaChar/Random.pm

@@ -0,0 +1,18 @@
+package JapaChar::Random;
+
+use v5.38.2;
+
+use strict;
+use warnings;
+
+use Moo;
+
+use Crypt::URandom qw( urandom );
+
+sub get($min = 1, $max = 100) {
+    my $rng = urandom(4);
+    $rng = unpack 'L', $rng;
+    $rng = ($rng % $max) + $min;
+    return $rng;
+}
+1;

t/01-characters.t

@@ -0,0 +1,28 @@
+#!/usr/bin/env perl
+
+use v5.38.2;
+
+use strict;
+use warnings;
+
+use Test::Most tests => 2;
+use Test::MockModule;
+use Path::Tiny;
+
+use File::Basename;
+
+use lib dirname(dirname(__FILE__)).'/lib';
+
+use JapaChar::DB;
+
+BEGIN {
+    use_ok 'JapaChar::Characters';
+};
+
+{
+    my $mock_db = Test::MockModule->new('JapaChar::DB');
+    $mock_db->mock(_db_path => sub {
+        return path(__FILE__)->parent->child('all-learned-basic-characters.db');
+    });
+    ok defined(JapaChar::Characters->new->next_char), 'The next char is defined.';
+}