diff --git a/tests/adapters/test_template.py b/tests/adapters/test_template.py
new file mode 100644
index 00000000..3dbef541
--- /dev/null
+++ b/tests/adapters/test_template.py
@@ -0,0 +1,17 @@
+from utils import make_fake_message
+
+
+def test_message_template():
+    from nonebot.adapters import MessageTemplate
+
+    Message = make_fake_message()
+
+    template = MessageTemplate("{a:custom}{b:text}{c:image}", Message)
+
+    @template.add_format_spec
+    def custom(input: str) -> str:
+        return input + "-custom!"
+
+    formatted = template.format(a="test", b="test", c="https://example.com/test")
+    assert formatted.extract_plain_text() == "test-custom!test"
+    assert str(formatted) == "test-custom!test[fake:image]"
diff --git a/tests/utils.py b/tests/utils.py
index d516665f..a8d0c0ed 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -18,14 +18,18 @@ def make_fake_message() -> Type["Message"]:
             return FakeMessage
 
         def __str__(self) -> str:
-            return self.data["text"]
+            return self.data["text"] if self.type == "text" else f"[fake:{self.type}]"
 
         @classmethod
         def text(cls, text: str):
             return cls("text", {"text": text})
 
+        @classmethod
+        def image(cls, url: str):
+            return cls("image", {"url": url})
+
         def is_text(self) -> bool:
-            return True
+            return self.type == "text"
 
     class FakeMessage(Message):
         @classmethod