diff --git a/config.json b/config.json
index 5c24fe1..300cc0f 100644
--- a/config.json
+++ b/config.json
@@ -1,6 +1,7 @@
 {
     "safe_mode": false,
     "loglevel": "info",
+    "show_test_result_images": true,
     "text":
     {
         "font": "fonts/Futura_Condensed_Extra_Bold.otf",
diff --git a/src/config.py b/src/config.py
index 23f7e3b..e2871b2 100644
--- a/src/config.py
+++ b/src/config.py
@@ -34,6 +34,7 @@
     "error": logging.ERROR,
 }
 loglevel = __logdict[config["loglevel"]]
+show_test_result_images = config["show_test_result_images"]
 
 pngcrush_enabled = config["optimization"]["pngcrush"]["enabled"]
 
diff --git a/src/generatecaption.py b/src/generatecaption.py
index 065d24a..1f416f5 100644
--- a/src/generatecaption.py
+++ b/src/generatecaption.py
@@ -85,13 +85,12 @@ def generate_caption_image(rawtext: str) -> Image.Image:
         config.bg_color,
     )
     # paste merged lines in the middle
-    caption.paste(
+    caption.alpha_composite(
         merged_lines,
         (
             (caption.width - merged_lines.width) // 2,
             (caption.height - merged_lines.height) // 2,
-        ),
-        merged_lines,
+        )
     )
     logging.debug(f"Added padding to caption, size: {caption.size}")
 
diff --git a/tests/test_generatecaption.py b/tests/test_generatecaption.py
new file mode 100644
index 0000000..d7674c0
--- /dev/null
+++ b/tests/test_generatecaption.py
@@ -0,0 +1,51 @@
+import unittest
+import sys
+from PIL import Image
+from src.generatecaption import generate_caption_image
+from src import config
+
+
+class TestGenerateCaption(unittest.TestCase):
+    show = config.show_test_result_images
+    def test_generate_caption_image_hu(self):
+        rawtext = "Árvíztűrő tükörfúrógép"
+        result = generate_caption_image(rawtext)
+        self.assertIsInstance(result, Image.Image)
+
+        if self.show:
+            result.show()
+
+    def test_generate_caption_image_emoji(self):
+        rawtext = ":3 <3 :+1: :skull: 🦊 🐱"
+        result = generate_caption_image(rawtext)
+        self.assertIsInstance(result, Image.Image)
+
+        if self.show:
+            result.show()
+
+    def test_generate_caption_image_long(self):
+        rawtext = "faliure after " * 32
+        result = generate_caption_image(rawtext)
+        self.assertIsInstance(result, Image.Image)
+
+        if self.show:
+            result.show()
+
+    def test_generate_caption_image_emote(self):
+        rawtext = "<:floraSmug:1112288234488201307> " * 40
+        result = generate_caption_image(rawtext)
+        self.assertIsInstance(result, Image.Image)
+
+        if self.show:
+            result.show()
+
+    def test_generate_caption_image_longword(self):
+        rawtext = "test_generate_caption_image_longword_" + "A" * 100 
+        result = generate_caption_image(rawtext)
+        self.assertIsInstance(result, Image.Image)
+
+        if self.show:
+            result.show()
+
+if __name__ == "__main__":
+    unittest.main()