mvn verify ends with:

Tests run: 6, Failures: 5, Errors: 0, Skipped: 0, Time elapsed: 23.182 s <<< FAILURE! - in org.jenkinsci.plugins.docker.commons.credentials.DockerServerCredentialsBindingTest

basics(org.jenkinsci.plugins.docker.commons.credentials.DockerServerCredentialsBindingTest)  Time elapsed: 3.73 s  <<< FAILURE!

java.lang.AssertionError: 

unexpected build status; build log was:

…

…

[p] Running shell script

+ ./basics-step1.sh

++ stat -c %a ****

stat: illegal option -- c

usage: stat [-FlLnqrsx] [-f format] [-t timefmt] [file ...]

+ '[' = 700 ']'

./basics-step1.sh: line 5: [: =: unary operator expected

NAME
     readlink, stat -- display file status

SYNOPSIS
     stat [-FLnq] [-f format | -l | -r | -s | -x] [-t timefmt] [file ...]
     readlink [-n] [file ...]
DESCRIPTION
     The stat utility displays information about the file pointed to by file.  Read, write or execute permissions of the named file are not required, but all directories listed in the path name leading to the
     file must be searchable.  If no argument is given, stat displays information about the file descriptor for standard input.

     When invoked as readlink, only the target of the symbolic link is printed.  If the given argument is not a symbolic link, readlink will print nothing and exit with an error.

     The information displayed is obtained by calling lstat(2) with the given argument and evaluating the returned structure.

     The options are as follows:

     -F      As in ls(1), display a slash (`/') immediately after each pathname that is a directory, an asterisk (`*') after each that is executable, an at sign (`@') after each symbolic link, a percent sign
             (`%') after each whiteout, an equal sign (`=') after each socket, and a vertical bar (`|') after each that is a FIFO.  The use of -F implies -l.

     -f format
             Display information using the specified format.  See the FORMATS section for a description of valid formats.

     -L      Use stat(2) instead of lstat(2).  The information reported by stat will refer to the target of file, if file is a symbolic link, and not to file itself.

     -l      Display output in ls -lT format.

     -n      Do not force a newline to appear at the end of each piece of output.

     -q      Suppress failure messages if calls to stat(2) or lstat(2) fail.  When run as readlink, error messages are automatically suppressed.

     -r      Display raw information.  That is, for all the fields in the stat structure, display the raw, numerical value (for example, times in seconds since the epoch, etc.).

     -s      Display information in ``shell output'', suitable for initializing variables.

     -t timefmt
             Display timestamps using the specified format.  This format is passed directly to strftime(3).

     -x      Display information in a more verbose way as known from some Linux distributions.