diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c1c4c2f..1b385a6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,15 +21,14 @@ jobs:
         printf 'Apt::Install-Recommends "false";\n' | tee -a /etc/apt/apt.conf
         apt-get update
         apt-get install -y python3-gi-cairo gir1.2-pango-1.0
+        apt-get install -y perl
     - name: check Python version
       run: |
         python3 --version
-    - name: smoke test
+    - name: run tests
       run: |
         export LC_ALL=C.UTF-8
-        ./ubanner --trim 'νιάου'
-        ./ubanner --full-screen 'νιάου'
-        ./ubanner --list-fonts
+        prove -v
 
   static:
     runs-on: ${{matrix.os}}
diff --git a/README b/README
index b9980e6..a41f824 100644
--- a/README
+++ b/README
@@ -3,19 +3,19 @@ Overview
 
 .. code:: console
 
-   $ ubanner --trim 'νιάου'
-                                         ░░░
-                                        ██░
-                                      ░█▒
+   $ ubanner --trim πανό
+                                                                   ░░░
+                                                                  ██░
+                                                                 █▒
 
-    ░░░░░     ░░     ░░░░░          ░░░░░░    ░░        ░░░░░       ░░░░░    ░░░
-      ▒██      ██░     ▒██        ▒██░░░▒██░ █▒      ▒██░  ░░██░      ▒██     ░██░
-      ▒██      ░██░    ▒██       ███     ▒███▒      ███       ██▒     ▒██      ░██
-      ▒██      ▒██░    ▒██      ░██░      ███      ░██░       ▒██░    ▒██       ██▒
-      ▒██     ░██░     ▒██      ▒██░      ▒██      ▒██░       ▒██░    ▒██       ██▒
-      ▒██    ▒██       ▒██      ░██▒      ███▒     ░██▒       ▒██     ▒██      ▒██░
-      ▒██  ▒█▒         ░██       ░██░    ▒▒▒██      ░██░     ▒██░     ░██     ▒██░
-      ▒███▒░            ░▒██▒      ▒██▒▒▒░  ░███▒     ░▒█▒▒▒█▒░         ▒██▒██▒░
+    ░░░░░░░░░░░░░░░░      ░░░░░░    ░░   ░░░░░     ░░          ░░░░░
+      ▒██      ▒██      ▒██░░░▒██░ █▒      ▒██      ██░     ▒██░  ░░██░
+      ▒██      ▒██     ███     ▒███▒       ▒██      ░██░   ███       ██▒
+      ▒██      ▒██    ░██░      ███        ▒██      ▒██░  ░██░       ▒██░
+      ▒██      ▒██    ▒██░      ▒██        ▒██     ░██░   ▒██░       ▒██░
+      ▒██      ▒██    ░██▒      ███▒       ▒██    ▒██     ░██▒       ▒██
+      ▒██      ▒██     ░██░    ▒▒▒██       ▒██  ▒█▒        ░██░     ▒██░
+    ▒▒███▒▒  ░▒███▒▒     ▒██▒▒▒░  ░███▒    ▒███▒░            ░▒█▒▒▒█▒░
 
 Dependencies
 ============
diff --git a/t/common.sh b/t/common.sh
new file mode 100644
index 0000000..f08d816
--- /dev/null
+++ b/t/common.sh
@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+
+# Copyright © 2024 Jakub Wilk <jwilk@jwilk.net>
+# SPDX-License-Identifier: MIT
+
+set -e -u
+
+dir="${0%/*}/.."
+prog="${UBANNER_TEST_TARGET:-"$dir/ubanner"}"
+
+is_unicode_locale()
+{
+    local charset=$'\u2591\u2592\u2588'
+    test ${#charset} -eq 3
+}
+
+# vim:ts=4 sts=4 sw=4 et ft=sh
diff --git a/t/full-screen.t b/t/full-screen.t
new file mode 100755
index 0000000..ad7ce81
--- /dev/null
+++ b/t/full-screen.t
@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+# Copyright © 2024 Jakub Wilk <jwilk@jwilk.net>
+# SPDX-License-Identifier: MIT
+
+set -e -u
+
+. "${0%/*}/common.sh"
+
+echo 1..1
+is_unicode_locale || {
+    echo 'non-Unicode locale' >&2
+    exit 1
+}
+if out=$("$prog" --full-screen $'\u10E3')
+then
+    sed -e 's/^/# /' <<< "$out"
+    echo ok 1
+else
+    echo not ok 1
+fi
+
+# vim:ts=4 sts=4 sw=4 et ft=sh
diff --git a/t/lists-fonts.t b/t/lists-fonts.t
new file mode 100755
index 0000000..d38d7ce
--- /dev/null
+++ b/t/lists-fonts.t
@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+# Copyright © 2024 Jakub Wilk <jwilk@jwilk.net>
+# SPDX-License-Identifier: MIT
+
+set -e -u
+
+. "${0%/*}/common.sh"
+
+echo 1..1
+if out=$("$prog" --list-fonts)
+then
+    sed -e 's/^/# /' <<< "$out"
+    echo ok 1
+else
+    echo not ok 1
+fi
+
+# vim:ts=4 sts=4 sw=4 et ft=sh
diff --git a/t/trim.t b/t/trim.t
new file mode 100755
index 0000000..99fe707
--- /dev/null
+++ b/t/trim.t
@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+# Copyright © 2024 Jakub Wilk <jwilk@jwilk.net>
+# SPDX-License-Identifier: MIT
+
+set -e -u
+
+. "${0%/*}/common.sh"
+
+echo 1..1
+is_unicode_locale || {
+    echo 'non-Unicode locale' >&2
+    exit 1
+}
+if out=$("$prog" --trim $'\u10E3')
+then
+    sed -e 's/^/# /' <<< "$out"
+    echo ok 1
+else
+    echo not ok 1
+fi
+
+# vim:ts=4 sts=4 sw=4 et ft=sh
diff --git a/ubanner b/ubanner
index b486e97..771ebb1 100755
--- a/ubanner
+++ b/ubanner
@@ -7,6 +7,7 @@
 import argparse
 import bisect
 import itertools
+import locale
 import shutil
 import signal
 import sys
@@ -62,7 +63,6 @@ def pango_render(text, size=(76, 24), font=None, font_size=None):
     PangoCairo.show_layout(ctx, layout)
     data = surface.get_data()
     stride = surface.get_stride()
-    charset = ' ░▒█'
     cdiv = 512 // len(charset)
     for y in range(ht // 2):
         s = ''
@@ -93,6 +93,13 @@ class act_list_fonts(argparse.Action):
                 seen.add(descr)
         sys.exit()
 
+encoding = locale.nl_langinfo(locale.CODESET)
+charset = ' ░▒█'
+try:
+    charset.encode(encoding, 'strict')
+except UnicodeError:
+    charset = ' +*#'
+
 def main():
     signal.signal(signal.SIGPIPE, signal.SIG_DFL)
     ap = argparse.ArgumentParser()