t/0[25]*.t: improve test coverage

Prove some calling restrictions for config_dirs and providers
and test another misusage of _plug_dir_source.

Signed-off-by: Jens Rehsack <sno@netbsd.org>

t/02-plugg.t

@@ -51,6 +51,7 @@ ok(File::ConfigDir::_plug_dir_source($pure_src, "0E0"), "registered pure plugin"
 
 ok(!File::ConfigDir::_plug_dir_source(),      "registered nothing");
 ok(!File::ConfigDir::_plug_dir_source(undef), "registered undef");
+ok(!File::ConfigDir::_plug_dir_source(42),    "registered 42");
 
 my @dirs = config_dirs();
 note("config_dirs: " . join(",", @dirs));

t/05-errors.t

@@ -0,0 +1,31 @@
+#!perl
+
+use strict;
+use warnings;
+
+use Test::More;
+
+use File::ConfigDir ();
+
+foreach my $fn (
+    qw(config_dirs system_cfg_dir desktop_cfg_dir),
+    qw(core_cfg_dir site_cfg_dir vendor_cfg_dir),
+    qw(local_cfg_dir here_cfg_dir vendorapp_cfg_dir),
+    qw(xdg_config_home user_cfg_dir locallib_cfg_dir),
+  )
+{
+    my $faddr = File::ConfigDir->can($fn);
+    eval { $faddr->(qw(foo bar)); };
+    my $exception = $@;
+    like($exception, qr/$fn\(;\$\), not $fn\(\$,\$\)/, "$fn throws exception on misuse");
+}
+
+foreach my $fn (qw(singleapp_cfg_dir))
+{
+    my $faddr = File::ConfigDir->can($fn);
+    eval { $faddr->(qw(foo bar)); };
+    my $exception = $@;
+    like($exception, qr/$fn\(\), not $fn\(\$,\$\)/, "$fn throws exception on misuse");
+}
+
+done_testing;