Bug 10277: Add UT for C4::Context::IsSuperLibrarian

Note that I modify the return value. Before this patch, it returned an
empty string or 1. Now it returns 0 or 1.

Test plan:
- same as the original patch
- verify that unit tests pass:
    prove t/Context.t

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes all tests and QA script, including new tests.
Checked the code and tested superlibrarian behaviour in some places:

moremember.pl:
With IndyBranches only superlibrarian can delete borrowers from
other branches. Accessing the borrower with a direct link.
OK

C4/Members.pm
With IndyBranches only superlibrarian can search for borrowres
from other branches.
OK

tools/holidays.pl
With IndyBranches only superlibrarian can edit holidays for other
branches.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 3e866d216d)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>

C4/Context.pm

@@ -1249,10 +1249,14 @@ sub tz {
 =cut
 
 sub IsSuperLibrarian {
-    my $userenv = C4::Context->userenv
-      || carp("C4::Context->userenv not defined!");
+    my $userenv = C4::Context->userenv;
 
-    return $userenv->{flags} % 2 == 1;
+    unless ( $userenv and exists $userenv->{flags} ) {
+      carp("C4::Context->userenv not defined!");
+      return 0;
+    }
+
+    return $userenv->{flags} % 2;
 }
 
 1;

t/Context.t

@@ -1,10 +1,32 @@
 #!/usr/bin/perl
-use strict;
-use warnings;
+
+use Modern::Perl;
 use DBI;
-use Test::More tests => 1;
+use Test::More tests => 6;
 use Test::MockModule;
 
 BEGIN {
     use_ok('C4::Context');
 }
+
+my $context = new Test::MockModule('C4::Context');
+my $userenv = {};
+
+$context->mock('userenv', sub {
+    return $userenv;
+});
+
+local $SIG{__WARN__} = sub { die $_[0] };
+
+eval { C4::Context::IsSuperLibrarian(); };
+like ( $@, qr/not defined/, "IsSuperLibrarian logs an error if no userenv is defined" );
+
+$userenv->{flags} = 42;
+my $is_super_librarian = eval{ C4::Context::IsSuperLibrarian() };
+is ( $@, q||, "IsSuperLibrarian does not log an error if userenv is defined" );
+is ( $is_super_librarian, 0, "With flag=42, it is not a super librarian" );
+
+$userenv->{flags} = 421;
+$is_super_librarian = eval{ C4::Context::IsSuperLibrarian() };
+is ( $@, q||, "IsSuperLibrarian does not log an error if userenv is defined" );
+is ( $is_super_librarian, 1, "With flag=1, it is a super librarian" );