NAME
    Test::MockFile - Lets tests validate code which interacts with files
    without the file system ever being touched.

VERSION
    Version 0.012

SYNOPSIS
    Intercepts file system calls for specific files so unit testing can take
    place without any files being altered on disk.

    This is useful for small tests
    <https://en.wikipedia.org/wiki/Google_Test#Small_Tests_(Unit_Tests)>
    where file interaction is discouraged.

    A strict mode is even provided which can throw a die when files are
    accessed during your tests!

        # Loaded before Test::MockModule so uses the core perl functions without any hooks.
        use Module::I::Dont::Want::To::Alter;

        use Test::MockFile;

        my $mock_file = Test::MockFile->file("/foo/bar", "contents\ngo\nhere");
        open(my $fh, "<", "/foo/bar") or die; # Does not actually open the file on disk.
        say "ok" if -e $fh;
        close $fh;
        say "ok" if (-f "/foo/bar");
        say "/foo/bar is THIS BIG: " . -s "/foo/bar"

        my $missing_mocked_file = Test::MockFile->file("/foo/baz"); # File starts out missing.
        my $opened = open(my $baz_fh, "<", "/foo/baz"); # File reports as missing so fails.
        say "ok" if !-e "/foo/baz";
    
        open($baz_fh, ">", "/foo/baz") or die; # open for writing
        print <$baz_fh> "replace contents\n";
    
        open($baz_fh, ">>", "/foo/baz") or die; # open for append.
        print <$baz_fh> "second line";
        close $baz_fh;
    
        say $baz->contents;
    
        # Unmock your file.
        undef $missing_mocked_file;
    
        # The file check will now happen on file system now the file is no longer mocked.
        say "ok" if !-e "/foo/baz";

IMPORT
    If the module is loaded in strict mode, any file checks, open, sysopen,
    opendir, stat, or lstat will throw a die.

    For example:

        use Test::MockFile qw/strict/;

        # This will not die.
        Test::MockFile->file("/bar", "...");
        Test::MockFile->link("/foo", "/bar");
        -l "/foo" or print "ok\n";
        open(my $fh, ">", "/foo");
    
        # All of these will die
        open(my $fh, ">", "/unmocked/file"); # Dies
        sysopen(my $fh, "/other/file", O_RDONLY);
        opendir(my $fh, "/dir");
        -e "/file";
        -l "/file"

SUBROUTINES/METHODS
  file
    Args: ($file, $contents, $stats)

    This will make cause $file to be mocked in all file checks, opens, etc.

    undef contents means that the file should act like it's not there.

    See "Mock Stats" for what goes in this hash ref.

  file_from_disk
    Args: "($file_to_mock, $file_on_disk, $stats)"

    This will make cause $file to be mocked in all file checks, opens, etc.

    If "file_on_disk" isn't present, then this will die.

    See "Mock Stats" for what goes in this hash ref.

  symlink
    Args: ($readlink, $file )

    This will cause $file to be mocked in all file checks, opens, etc.

    $readlink indicates what "fake" file it points to. If the file $readlink
    points to is not mocked, it will act like a broken link, regardless of
    what's on disk.

    If $readlink is undef, then the symlink is mocked but not present.(lstat
    $file is empty.)

    Stats are not able to be specified on instantiation but can in theory be
    altered after the object is created. People don't normally mess with the
    permissions on a symlink.

  dir
    Args: ($dir, \@contents, $stats)

    This will cause $dir to be mocked in all file checks, and opendir
    interactions.

    @contents should be provided in the sort order you expect to see the
    files from readdir. NOTE: Because "." and ".." will always be the first
    things readdir returns, These files are automatically inserted at the
    front of the array.

    See "Mock Stats" for what goes in this hash ref.

  Mock Stats
    When creating mocked files or directories, we default their stats to:

        Test::MockModule->new( $file, $contents, {
                'dev'       => 0,        # stat[0]
                'inode'     => 0,        # stat[1]
                'mode'      => $mode,    # stat[2]
                'nlink'     => 0,        # stat[3]
                'uid'       => 0,        # stat[4]
                'gid'       => 0,        # stat[5]
                'rdev'      => 0,        # stat[6]
                'atime'     => $now,     # stat[8]
                'mtime'     => $now,     # stat[9]
                'ctime'     => $now,     # stat[10]
                'blksize'   => 4096,     # stat[11]
                'fileno'    => undef,    # fileno()
        };

    You'll notice that mode, size, and blocks have been left out of this.
    Mode is set to 666 (for files) or 777 (for directories), xored against
    the current umask. Size and blocks are calculated based on the size of
    'contents' a.k.a. the fake file.

    When you want to override one of the defaults, all you need to do is
    specify that when you declare the file or directory. The rest will
    continue to default.

        Test::MockModule->file("/root/abc", "...", {inode => 65, uid => 123, mtime => int((2000-1970) * 365.25 * 24 * 60 * 60 }));

        Test::MockModule->dir("/sbin", "...", { mode => 0700 }));

  new
    This class method is called by file/symlink/dir. There is no good reason
    to call this directly.

  contents
    Optional Arg: $contents

    Reports or updates the current contents of the file.

    To update, pass an array ref of strings for a dir or a string for a
    file. Symlinks have no contents.

  unlink
    Makes the virtual file go away. NOTE: This also works for directories.

  touch
    Optional Args: ($epoch_time)

    This function acts like the UNIX utility touch. It sets atime, mtime,
    ctime to $epoch_time.

    If no arguments are passed, $epoch_time is set to time(). If the file
    does not exist, contents are set to an empty string.

  stat
    Returns the stat of a mocked file (does not follow symlinks.)

  readlink
    Optional Arg: $readlink

    Returns the stat of a mocked file (does not follow symlinks.) You can
    also use this to change what your symlink is pointing to.

  is_link
    returns true/false, depending on whether this object is a symlink.

  is_dir
    returns true/false, depending on whether this object is a directory.

  is_file
    returns true/false, depending on whether this object is a regular file.

  size
    returns the size of the file based on its contents.

  exists
    returns true or false base on if the file exists right now.

  blocks
    Calculates the block count of the file based on its size.

  chmod
    Optional Arg: $perms

    Allows you to alter the permissions of a file. This only allows you to
    change the 07777 bits of the file permissions. The number passed should
    be the octal 0755 form, not the alphabetic "755" form

  permissions
    Returns the permissions of the file.

  mtime
    Optional Arg: $new_epoch_time

    Returns and optionally sets the mtime of the file if passed as an
    integer.

  ctime
    Optional Arg: $new_epoch_time

    Returns and optionally sets the ctime of the file if passed as an
    integer.

  atime
    Optional Arg: $new_epoch_time

    Returns and optionally sets the atime of the file if passed as an
    integer.

  add_file_access_hook
    Args: ( $code_ref )

    You can use add_file_access_hook to add a code ref that gets called
    every time a real file (not mocked) operation happens. We use this for
    strict mode to die if we detect your program is unexpectedly accessing
    files. You are welcome to use it for whatever you like.

    Whenever the code ref is called, we pass 2 arguments:
    "$code->($access_type, $at_under_ref)". Be aware that altering the
    variables in $at_under_ref will affect the variables passed to open /
    sysopen, etc.

    One use might be:

        Test::MockFile::add_file_access_hook(sub { my $type = shift; print "$type called at: " . Carp::longmess() } );

  clear_file_access_hooks
    Calling this subroutine will clear everything that was passed to
    add_file_access_hook

  How this mocking is done:
    Test::MockModule uses 2 methods to mock file access:

   -X via Overload::FileCheck
    It is currently not possible in pure perl to override stat
    <http://perldoc.perl.org/functions/stat.html>, lstat
    <http://perldoc.perl.org/functions/lstat.html> and -X operators
    <http://perldoc.perl.org/functions/-X.html>. In conjunction with this
    module, we've developed Overload::FileCheck.

    This enables us to intercept calls to stat, lstat and -X operators (like
    -e, -f, -d, -s, etc.) and pass them to our control. If the file is
    currently being mocked, we return the stat (or lstat) information on the
    file to be used to determine the answer to whatever check was made. This
    even works for things like "-e _". If we do not control the file in
    question, we return "FALLBACK_TO_REAL_OP()" which then makes a normal
    check.

   CORE::GLOBAL:: overrides
    Since 5.10, it has been possible to override function calls by defining
    them. like:

        *CORE::GLOBAL::open = sub(*;$@) {...}

    Any code which is loaded AFTER this happens will use the alternate open.
    This means you can place your "use Test::MockFile" statement after
    statements you don't want mocked and there is no risk that that code
    will ever be altered by Test::MockModule.

    We oveload the following statements and then return tied handles to
    enable the rest of the IO functions to work properly. Only open /
    sysopen are needed to address file operations. However opendir file
    handles were never setup for tie so we have to override all of opendir's
    related functions.

    *   open

    *   sysopen

    *   opendir

    *   readdir

    *   telldir

    *   seekdir

    *   rewinddir

    *   closedir

AUTHOR
    Todd Rinaldo, "<toddr at cpan.org>"

BUGS
    Please report any bugs or feature requests to
    <https://github.com/CpanelInc/Test-MockFile>.

SUPPORT
    You can find documentation for this module with the perldoc command.

        perldoc Test::MockFile

    You can also look for information at:

    *   CPAN Ratings

        <https://cpanratings.perl.org/d/Test-MockFile>

    *   Search CPAN

        <https://metacpan.org/release/Test-MockFile>

ACKNOWLEDGEMENTS
    Thanks to Nicolas R., "<atoomic at cpan.org>" for help with
    Overload::FileCheck. This module could not have been completed without
    it.

LICENSE AND COPYRIGHT
    Copyright 2018 cPanel L.L.C.

    All rights reserved.

    <http://cpanel.net>

    This is free software; you can redistribute it and/or modify it under
    the same terms as Perl itself. See perlartistic.

