diff --git a/src/procleaning_mcp/__pycache__/server.cpython-311.pyc b/src/procleaning_mcp/__pycache__/server.cpython-311.pyc
new file mode 100644
index 0000000..7a192d4
Binary files /dev/null and b/src/procleaning_mcp/__pycache__/server.cpython-311.pyc differ
diff --git a/src/procleaning_mcp/server.py b/src/procleaning_mcp/server.py
index d08558f..2954849 100644
--- a/src/procleaning_mcp/server.py
+++ b/src/procleaning_mcp/server.py
@@ -158,9 +158,9 @@ def system_resource_usage(top_n: int = 10, sort_by: str = "cpu") -> str:
     threads = psutil.cpu_count(logical=True) or 1
 
     key_map = {
-        "cpu": lambda p: p.cpu_percent(),
-        "memory": lambda p: p.memory_percent(),
-        "rss": lambda p: p.memory_info().rss,
+        "cpu": lambda p: p["cpu_percent"],
+        "memory": lambda p: p["memory_percent"],
+        "rss": lambda p: p["memory_rss_mb"],
     }
     sort_key = key_map.get(sort_by, key_map["cpu"])
 
diff --git a/tests/test_server.py b/tests/test_server.py
new file mode 100644
index 0000000..34982de
--- /dev/null
+++ b/tests/test_server.py
@@ -0,0 +1,90 @@
+"""Tests for procleaning-mcp server."""
+
+import sys
+import asyncio
+import os
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "src"))
+
+import pytest
+from procleaning_mcp.server import mcp
+
+
+@pytest.fixture
+def event_loop():
+    """Create a test event loop."""
+    loop = asyncio.new_event_loop()
+    yield loop
+    loop.close()
+
+
+@pytest.mark.asyncio
+async def test_list_processes():
+    """Test that list_processes returns valid output."""
+    result = await mcp.call_tool(
+        "list_processes", {"name_filter": "python", "max_processes": 5}
+    )
+    # call_tool returns (content_list, structured_content)
+    content_list, structured = result
+    assert isinstance(content_list, list)
+    assert content_list[0].type == "text"
+    text = content_list[0].text
+    assert "Found" in text or "No processes" in text
+
+
+@pytest.mark.asyncio
+async def test_system_resource_usage():
+    """Test that system_resource_usage returns valid output."""
+    result = await mcp.call_tool(
+        "system_resource_usage", {"top_n": 3, "sort_by": "memory"}
+    )
+    content_list, structured = result
+    assert isinstance(content_list, list)
+    assert content_list[0].type == "text"
+    text = content_list[0].text
+    assert "CPU Usage" in text
+    assert "Memory Usage" in text
+    assert "Top 3" in text
+
+
+@pytest.mark.asyncio
+async def test_find_zombies():
+    """Test that find_zombies returns valid output."""
+    result = await mcp.call_tool("find_zombies", {"include_details": False})
+    content_list, structured = result
+    assert isinstance(content_list, list)
+    assert content_list[0].type == "text"
+
+
+@pytest.mark.asyncio
+async def test_list_processes_empty_filter():
+    """Test list_processes with no filter returns processes."""
+    result = await mcp.call_tool(
+        "list_processes", {"max_processes": 3}
+    )
+    content_list, structured = result
+    assert isinstance(content_list, list)
+    text = content_list[0].text
+    assert "Found" in text
+
+
+@pytest.mark.asyncio
+async def test_kill_process_no_confirm():
+    """Test that kill_process without confirm returns cancellation message."""
+    result = await mcp.call_tool(
+        "kill_process", {"pid": 1, "confirm": False}
+    )
+    content_list, structured = result
+    text = content_list[0].text
+    assert "cancelled" in text.lower()
+
+
+@pytest.mark.asyncio
+async def test_kill_by_name_no_match():
+    """Test kill_by_name with non-existent process name."""
+    result = await mcp.call_tool(
+        "kill_by_name", {"name_pattern": "thisprocessdoesnotexist12345", "confirm": False}
+    )
+    content_list, structured = result
+    text = content_list[0].text
+    assert "cancelled" in text.lower()