diff --git a/lib/Zonemaster/Engine/Test.pm b/lib/Zonemaster/Engine/Test.pm
index 967994a96..fcee53131 100644
--- a/lib/Zonemaster/Engine/Test.pm
+++ b/lib/Zonemaster/Engine/Test.pm
@@ -27,6 +27,8 @@ use File::ShareDir qw[dist_file];
 use File::Slurp qw[read_file];
 use Scalar::Util qw[blessed];
 use POSIX qw[strftime];
+use Carp;
+use List::MoreUtils qw(any);
 
 =head1 NAME
 
@@ -136,6 +138,53 @@ sub _log_versions {
 
 =over
 
+=item install()
+
+    Zonemaster::Engine::Test->install_custom_test_module('My::Module');
+
+Installs a custom module outside of the C<Zonemaster::Engine::Test::> namespace.
+This module must be a modules that implements the same interface as the modules
+in that namespace (ie. C<version()> C<all()> etc).
+
+The effective profile will be updated to include all test cases from the custom
+module.
+
+=back
+
+=cut
+
+sub install_custom_test_module {
+    my ( $class, $module ) = @_;
+
+    $module->import();
+
+    # get list of cases to be added
+    my @cases = keys( %{$module->metadata} );
+
+    my $profile = Zonemaster::Engine::Profile->effective;
+
+    # check there isn't a collission between one of the new cases and an
+    # existing case
+    foreach my $case ( @cases ) {
+        if ( any { $_ eq $case } @{$profile->{profile}->{test_cases}} ) {
+            carp sprintf "case '%s' already exists", $case ;
+            return undef;
+        }
+    }
+
+    # add the module
+    push @all_test_modules, $module;
+
+    # append cases to the profile
+    push @{$profile->{profile}->{test_cases}}, @cases;
+
+    return 1;
+}
+
+=pod
+
+=over
+
 =item modules()
 
     my @modules_array = modules();
@@ -197,7 +246,7 @@ sub run_all_for {
 
     if ( Zonemaster::Engine::Test::Basic->can_continue( $zone, @results ) and Zonemaster::Engine->can_continue() ) {
         foreach my $mod ( __PACKAGE__->modules ) {
-            my $module = "Zonemaster::Engine::Test::$mod";
+            my $module = ( $mod =~ /::/ ? $mod : "Zonemaster::Engine::Test::$mod" );
             info( MODULE_VERSION => { module => $module, version => $module->version } );
             my @res = eval { $module->all( $zone ) };
             if ( $@ ) {
@@ -259,7 +308,7 @@ sub run_module {
 
     if ( Zonemaster::Engine->can_continue() ) {
         if ( $module ) {
-            my $m = "Zonemaster::Engine::Test::$module";
+            my $m = ( $module =~ /::/ ? $module : "Zonemaster::Engine::Test::$module" );
             info( MODULE_VERSION => { module => $m, version => $m->version } );
             push @res, eval { $m->all( $zone ) };
             if ( $@ ) {
@@ -323,7 +372,7 @@ sub run_one {
 
     if ( Zonemaster::Engine->can_continue() ) {
         if ( $module ) {
-            my $m = "Zonemaster::Engine::Test::$module";
+            my $m = ( $module =~ /::/ ? $module : "Zonemaster::Engine::Test::$module" );
             if ( $m->metadata->{$test} and Zonemaster::Engine::Util::should_run_test( $test ) ) {
                 info( MODULE_VERSION => { module => $m, version => $m->version } );
                 push @res, eval { $m->$test( $zone ) };
diff --git a/t/custom.module b/t/custom.module
new file mode 100755
index 000000000..fabb8737c
--- /dev/null
+++ b/t/custom.module
@@ -0,0 +1,63 @@
+package My::Module;
+use strict;
+use vars qw($VERSION %TAG_DESCRIPTIONS);
+use Zonemaster::Engine::Util;
+use Locale::TextDomain qw(Zonemaster-Engine);
+use warnings;
+
+$VERSION = q{1.0.0};
+
+%TAG_DESCRIPTIONS = (
+    TEST_CASE_START => sub { __x('TEST_CASE_START {testcase}.', @_) },
+    TEST_CASE_END   => sub { __x('TEST_CASE_END {testcase}.', @_) },
+    THIS_IS_A_TEST  => sub { __x('THIS IS A TEST.', @_) },
+);
+
+sub version {
+    return $VERSION;
+}
+
+sub metadata {
+    my ( $class ) = @_;
+    return {
+        test01 => [qw(
+            TEST_CASE_START
+            TEST_CASE_END
+            THIS_IS_A_TEST
+        )],
+    };
+}
+
+sub tag_descriptions {
+    return \%TAG_DESCRIPTIONS;
+}
+
+sub all {
+    my ( $class, $zone ) = @_;
+
+    my @results;
+
+    push @results, $class->test01( $zone ) if Zonemaster::Engine::Util::should_run_test(q{test01});
+
+    return @results;
+}
+
+sub test01 {
+    my ( $class, $zone ) = @_;
+
+    my @results;
+
+    push(@results, _emit_log(TEST_CASE_START => {testcase => q{test01}}));
+
+    push(@results, _emit_log(THIS_IS_A_TEST => {}));
+
+    push(@results, _emit_log(TEST_CASE_END => {testcase => q{test01}}));
+
+    return @results;
+}
+
+sub _emit_log {
+    return Zonemaster::Engine->logger->add(@_[0..1], __PACKAGE__);
+}
+
+1;
diff --git a/t/custom.t b/t/custom.t
new file mode 100644
index 000000000..d60f78ca1
--- /dev/null
+++ b/t/custom.t
@@ -0,0 +1,35 @@
+use Cwd qw(abs_path);
+use List::Util qw(any);
+use File::Spec;
+use File::Basename qw(dirname);
+use Test::More;
+use strict;
+use warnings;
+
+BEGIN {
+    use_ok( q{Zonemaster::Engine} );
+    use_ok( q{Zonemaster::Engine::Nameserver} );
+}
+
+my $module  = 'My::Module';
+
+my $modfile = abs_path( File::Spec->catfile(
+    dirname( __FILE__ ),
+    'custom.module'
+) );
+
+require_ok $modfile;
+
+$module->import();
+
+Zonemaster::Engine::Test->install_custom_test_module( $module );
+
+ok any { $_ eq $module } Zonemaster::Engine::Test->modules();
+
+my @results = Zonemaster::Engine->test_module( $module, q{example.com} );
+
+ok scalar @results > 0;
+
+ok scalar ( grep { 'THIS_IS_A_TEST' eq $_->tag } @results ) > 0;
+
+done_testing;