Test cannot detect missing lang item in array

[kenjis]

CLI.generator.viewName.cell is missing in ja, but tests pass. See https://codeigniter4.github.io/translations/ja.html

en:

return [
    'altCommandPlural'   => 'Did you mean one of these?',
    'altCommandSingular' => 'Did you mean this?',
    'commandNotFound'    => 'Command "{0}" not found.',
    'generator'          => [
        // ...
        'usingCINamespace' => 'Warning: Using the "CodeIgniter" namespace will generate the file in the system directory.',
        'viewName'         => [
            'cell' => 'Cell view name',
        ],
    ],
    // ...

ja:

return [
    'altCommandPlural'   => 'この中の1つですか？', // 'Did you mean one of these?'
    'altCommandSingular' => 'これですか？', // 'Did you mean this?'
    'commandNotFound'    => '"{0}" というコマンドはありません。', // 'Command "{0}" not found.'
    'generator'          => [
        // ...
        'usingCINamespace' => '警告: 名前空間 "CodeIgniter" を使用するとsystemディレクトリにファイルが生成されます。', // 'Warning: Using the "CodeIgniter" namespace will generate the file in the system directory.'
    ],
    // ...

[Terrorboy]

[paulbalandan]

It seems array_diff_key in testAllConfiguredLanguageKeysAreIncluded is not enough to detect multi-level arrays.