diff --git a/Makefile.PL b/Makefile.PL
index 7a3298e..7d455d3 100644
--- a/Makefile.PL
+++ b/Makefile.PL
@@ -7,18 +7,19 @@ WriteMakefile(
     NAME           => 'qpsmtpd',
     VERSION_FROM   => 'lib/Qpsmtpd.pm',
     PREREQ_PM      => {
-        'Data::Dumper' => 0,
-        'Date::Parse'  => 0,
-        'File::Temp'   => 0,
-        'Mail::Header' => 0,
-        'MIME::Base64' => 0,
-        'Net::DNS'     => 0.39,
-        'Net::IP'      => 0,
-        'Time::HiRes'  => 0,
+        'CDB_File'        => 0,
+        'Data::Dumper'    => 0,
+        'Date::Parse'     => 0,
+        'File::Temp'      => 0,
+        'Mail::Header'    => 0,
+        'MIME::Base64'    => 0,
+        'Net::DNS'        => 0.39,
+        'Net::IP'         => 0,
+        'Time::HiRes'     => 0,
         'IO::Socket::SSL' => 0,
 # Dev/Test modules
-	    'Test::More'   => 0,
-	    'Test::Output' => 0,
+	    'Test::More'      => 0,
+	    'Test::Output'    => 0,
 # modules for specific features
         'Mail::DKIM'         => 0,
         'File::Tail'         => 0,   # log/summarize, log/watch
diff --git a/lib/Qpsmtpd/Config.pm b/lib/Qpsmtpd/Config.pm
index 1055c84..021315c 100644
--- a/lib/Qpsmtpd/Config.pm
+++ b/lib/Qpsmtpd/Config.pm
@@ -8,7 +8,7 @@ use lib 'lib';
 use parent 'Qpsmtpd::Base';
 use Qpsmtpd::Constants;
 
-our $_config_cache = {};
+our %config_cache = ();
 our %dir_memo;
 our %defaults = (
                 me      => hostname,
@@ -43,7 +43,7 @@ sub config_dir {
 }
 
 sub clear_cache {
-    $_config_cache = {};
+    %config_cache = ();
     %dir_memo = ();
 }
 
@@ -72,7 +72,8 @@ sub get_qmail_map {
     my ($self, $config, $configfile) = @_;
 
     if (!-e $configfile . ".cdb") {
-        $_config_cache->{$config} ||= [];
+        $self->log(LOGERROR, "File $configfile.cdb does not exist");
+        $config_cache{$config} ||= [];
         return +{};
     }
     eval { require CDB_File };
@@ -99,7 +100,7 @@ sub get_qmail_map {
 sub from_file {
     my ($self, $configfile, $config, $visited) = @_;
     if (!-e $configfile) {
-        $_config_cache->{$config} ||= [];
+        $config_cache{$config} ||= [];
         return;
     }
 
@@ -145,7 +146,7 @@ sub from_file {
             }
             push @{$visited}, $inclusion;
 
-            for my $inc ($self->expand_inclusion_($inclusion, $configfile)) {
+            for my $inc ($self->expand_inclusion($inclusion, $configfile)) {
                 my @insertion = $self->from_file($inc, $config, $visited);
                 splice @config, $pos, 0, @insertion;    # insert the inclusion
                 $pos += @insertion;
@@ -156,12 +157,12 @@ sub from_file {
         }
     }
 
-    $_config_cache->{$config} = \@config;
+    $config_cache{$config} = \@config;
 
     return wantarray ? @config : $config[0];
 }
 
-sub expand_inclusion_ {
+sub expand_inclusion {
     my $self      = shift;
     my $inclusion = shift;
     my $context   = shift;
diff --git a/t/config/users.cdb b/t/config/users.cdb
new file mode 100644
index 0000000..507dbf9
Binary files /dev/null and b/t/config/users.cdb differ
diff --git a/t/qpsmtpd-config.t b/t/qpsmtpd-config.t
index fc99c4c..a547888 100644
--- a/t/qpsmtpd-config.t
+++ b/t/qpsmtpd-config.t
@@ -4,6 +4,7 @@ use warnings;
 use Data::Dumper;
 use File::Path;
 use Test::More;
+use Sys::Hostname;
 
 use lib 'lib';    # test lib/Qpsmtpd (vs site_perl)
 use lib 't';
@@ -30,8 +31,12 @@ isa_ok($config, 'Qpsmtpd::Config');
 
 __log();
 __config_dir();
+__clear_cache();
+__default();
 __from_file();
 __get_qmail();
+__get_qmail_map();
+__expand_inclusion();
 __config_via_smtpd();
 
 foreach my $f (@mes) { unlink $f; }
@@ -52,26 +57,55 @@ sub __log {
     is($warned, "$$ test log message\n", 'LOGWARN emitted correct warning');
 }
 
+sub __config_dir {
+    my $dir = $config->config_dir('logging');
+    ok($dir, "config_dir, $dir");
+
+    #warn Data::Dumper::Dumper($Qpsmtpd::config_dir_memo{logging});
+    $dir = $Qpsmtpd::Config::dir_memo{logging};
+    ok($dir, "config_dir, $dir (memo)");
+}
+
+sub __clear_cache {
+    $Qpsmtpd::Config::config_cache{foo} = 2;
+    $Qpsmtpd::Config::dir_memo{dir1} = 'some/path';
+
+    $config->clear_cache();
+    ok(! $Qpsmtpd::Config::config_cache{foo}, "clear_cache, config_cache")
+        or diag Data::Dumper::Dumper($Qpsmtpd::Config::config_cache{foo});
+    ok(! $Qpsmtpd::Config::dir_memo{dir1}, "clear_cache, dir_memo")
+};
+
+sub __default {
+    is($config->default('me'), hostname, "default, my hostname");
+    is($config->default('timeout'), 1200, "default timeout is 1200");
+    ok(!$config->default('undefined-test'), "default, undefined");
+}
+
 sub __get_qmail {
     is($config->get_qmail('me'), 'host.example.org', 'get_qmail("me")');
     ok(!$config->get_qmail('not-me'), 'get_qmail("not-me")');
 }
 
+sub __get_qmail_map {
+    eval "require CDB_File";   ## no critic (StringyEval)
+    if (!$@) {
+        my $r = $config->get_qmail_map('users', 't/config/users');
+        ok(keys %$r, 'get_qmail_map("users.cdb")');
+        ok($r->{'!example.com-'}, "get_qmail_map, known entry");
+    };
+}
+
 sub __from_file {
     my $test_file = 't/config/test_config_file';
     my @r = $config->from_file($test_file, 'test_config_file');
     ok( @r, "from_file, $test_file");
     cmp_ok('1st line with content', 'eq', $r[0], "from_file string compare");
     ok( !$r[1], "from_file");
-};
+}
 
-sub __config_dir {
-    my $dir = $config->config_dir('logging');
-    ok($dir, "config_dir, $dir");
-
-    #warn Data::Dumper::Dumper($Qpsmtpd::config_dir_memo{logging});
-    $dir = $Qpsmtpd::Config::dir_memo{logging};
-    ok($dir, "config_dir, $dir (memo)");
+sub __expand_inclusion {
+    # TODO
 }
 
 sub __config_via_smtpd {