Add missing tests

src/fastmcp/utilities/types.py

@@ -234,7 +234,11 @@ class File:
     def _get_mime_type(self) -> str:
         """Get MIME type from format or guess from file extension."""
         if self._format:
-            return f"application/{self._format.lower()}"
+            fmt = self._format.lower()
+            # Map common text formats to text/plain
+            if fmt in {"plain", "txt", "text"}:
+                return "text/plain"
+            return f"application/{fmt}"
 
         if self.path:
             mime_type, _ = mimetypes.guess_type(self.path)

tests/server/test_server_interactions.py

@@ -99,6 +99,11 @@ def tool_server():
             TextContent(type="text", text="direct content"),
         ]
 
+    @mcp.tool
+    def file_text_tool() -> File:
+        # Return a File with text data and text/plain format
+        return File(data=b"hello world", format="plain")
+
     return mcp
 
 
@@ -110,7 +115,7 @@ class TestTools:
 
     async def test_list_tools(self, tool_server: FastMCP):
         async with Client(tool_server) as client:
-            assert len(await client.list_tools()) == 10
+            assert len(await client.list_tools()) == 11
 
     async def test_call_tool(self, tool_server: FastMCP):
         async with Client(tool_server) as client:
@@ -151,6 +156,17 @@ class TestTools:
             result = await client.call_tool("list_tool", {})
             assert result[0].text == '[\n  "x",\n  2\n]'  # type: ignore[attr-defined]
 
+    async def test_file_text_tool(self, tool_server: FastMCP):
+        async with Client(tool_server) as client:
+            result = await client.call_tool("file_text_tool", {})
+            assert len(result) == 1
+            embedded = result[0]
+            assert isinstance(embedded, EmbeddedResource)
+            resource = embedded.resource
+            assert isinstance(resource, TextResourceContents)
+            assert resource.mimeType == "text/plain"
+            assert resource.text == "hello world"
+
 
 class TestToolTags:
     def create_server(self, include_tags=None, exclude_tags=None):

tests/tools/test_tool.py

@@ -502,6 +502,19 @@ class TestConvertResultToContent:
         # Convert URI to string for startswith check
         assert str(resource.uri).startswith("file:///resource.octet-stream")
 
+    def test_file_object_text_result(self):
+        """Test that a File object with text data is converted to EmbeddedResource with TextResourceContents."""
+        file_obj = File(data=b"sometext", format="plain")
+        result = _convert_to_content(file_obj)
+        assert isinstance(result, list)
+        assert len(result) == 1
+        assert isinstance(result[0], EmbeddedResource)
+        assert result[0].type == "resource"
+        resource = result[0].resource
+        assert isinstance(resource, TextResourceContents)
+        assert resource.mimeType == "text/plain"
+        assert resource.text == "sometext"
+
     def test_basic_type_result(self):
         """Test that a basic type is converted to TextContent."""
         result = _convert_to_content(123)

tests/utilities/test_types.py

@@ -3,7 +3,7 @@ from types import EllipsisType
 from typing import Annotated, Any
 
 import pytest
-from mcp.types import BlobResourceContents
+from mcp.types import BlobResourceContents, TextResourceContents
 
 from fastmcp.utilities.types import (
     Audio,
@@ -382,6 +382,17 @@ class TestFile:
         if isinstance(resource.resource, BlobResourceContents):
             assert resource.resource.blob == base64.b64encode(test_data).decode()
 
+    def test_to_resource_content_with_text_data(self):
+        """Test conversion to ResourceContent with text data (TextResourceContents)."""
+        test_data = b"hello world"
+        file = File(data=test_data, format="plain")
+        resource = file.to_resource_content()
+        assert resource.type == "resource"
+        # Should be TextResourceContents for text/plain
+        assert isinstance(resource.resource, TextResourceContents)
+        assert resource.resource.mimeType == "text/plain"
+        assert resource.resource.text == "hello world"
+
     def test_to_resource_content_error(self, monkeypatch):
         """Test error case in to_resource_content."""
         file = File(data=b"test")