Ensuring the first characters and db population work with a test.

lib/JapaChar/Characters.pm

@@ -35,13 +35,16 @@ WHERE name = ?', {}, $option_populated
 sub _populate_type( $self, $type ) {
     my $basic_character_resultset =
       JapaChar::Schema->Schema->resultset('BasicCharacter');
+    my @array_for_insertion;
     for my $char ( @{ $self->_get_characters_of_type($type) } ) {
         my $kana    = $char->{kana};
         my $romanji = $char->{roumaji};
         next if $romanji =~ /pause/i;
-        $basic_character_resultset->new(
-            { value => $kana, romanji => $romanji, type => $type, } )->insert;
+        push @array_for_insertion, { value => $kana, romanji => $romanji, type => $type };
     }
+    $basic_character_resultset->populate([
+        @array_for_insertion
+    ]);
 }
 
 sub _get_characters_of_type( $self, $type ) {

lib/JapaChar/DB.pm

@@ -16,6 +16,10 @@ use Data::Dumper;
 
 my $dbh;
 
+sub reset_dbh {
+    undef $dbh;
+}
+
 sub connect {
     if ( defined $dbh ) {
         return $dbh;

lib/JapaChar/Schema.pm

@@ -29,4 +29,8 @@ sub Schema ($class) {
     }
     return $schema;
 }
+
+sub reset_schema {
+    undef $schema;
+}
 1;

t/01-characters.t

@@ -5,7 +5,7 @@ use v5.38.2;
 use strict;
 use warnings;
 
-use Test::Most tests => 3;
+use Test::Most tests => 5;
 use Test::MockModule;
 use Path::Tiny;
 
@@ -15,6 +15,7 @@ use lib dirname(dirname(__FILE__)).'/lib';
 
 use JapaChar::DB;
 use JapaChar::Random;
+use JapaChar::Schema;
 
 BEGIN {
     use_ok 'JapaChar::Characters';
@@ -37,5 +38,29 @@ BEGIN {
     });
     my $next_char = JapaChar::Characters->new->next_char;
     ok defined($next_char), 'The next char is defined.';
-    is_deeply $next_review_char, $next_char, 'The next char is a review one.';
+    is_deeply $next_char, $next_review_char, 'The next char is a review one when all characters are learned.';
+}
+
+{
+    JapaChar::Schema::reset_schema();
+    JapaChar::DB::reset_dbh();
+    my $mock_db = Test::MockModule->new('JapaChar::DB');
+    my $tempdir = Path::Tiny->tempdir;
+    my $db_file = $tempdir->child('doesnt-exist.db');
+    $mock_db->mock(_db_path => sub {
+        return $db_file;
+    });
+    my $mock_random = Test::MockModule->new('JapaChar::Random');
+    $mock_random->mock(get => sub {
+        return 19;
+    });
+    my $mock_characters = Test::MockModule->new('JapaChar::Characters');
+    my $next_learning = undef;
+    $mock_characters->mock(_next_learning_char => sub {
+        $next_learning = $mock_characters->original('_next_learning_char')->(@_);
+        return $next_learning;
+    });
+    my $next_char = JapaChar::Characters->new->next_char;
+    ok defined($next_char), 'The next char is defined.';
+    is_deeply $next_char, $next_learning, 'The next char is a learning one when there is no progress.';
 }