From 1f51d878c8e30ee9e24b67846d8d4e0b9ccb74b1 Mon Sep 17 00:00:00 2001
From: GitHub Copilot <copilot@github.com>
Date: Sat, 24 Jan 2026 11:33:27 +0000
Subject: [PATCH] Add CPU sparkline to dashboard in compose mode

- New docker_stats.py module reads container stats from Docker socket
  using only asyncio + stdlib (no new dependencies)
- Calculates CPU % from delta of cpu_usage and system_cpu_usage
- Maintains ring buffer of last 30 CPU readings per container
- render_sparkline_svg() generates mini SVG chart from history
- DockerStatsCollector polls containers every 2 seconds
- New /cpu-sparkline.svg endpoint serves sparkline for a container
- Dashboard shows sparkline in tile header next to container name
- Only active in compose mode (--compose-manifest flag)
- Graceful degradation if Docker socket unavailable

Bump version to 0.1.17
---
 pyproject.toml                      |   2 +-
 src/textual_webterm/cli.py          |   3 +
 src/textual_webterm/docker_stats.py | 240 ++++++++++++++++++++++++++++
 src/textual_webterm/local_server.py |  66 +++++++-
 tests/test_docker_stats.py          | 209 ++++++++++++++++++++++++
 5 files changed, 517 insertions(+), 3 deletions(-)
 create mode 100644 src/textual_webterm/docker_stats.py
 create mode 100644 tests/test_docker_stats.py

diff --git a/pyproject.toml b/pyproject.toml
index 2f3f73c..cac8954 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "textual-webterm"
-version = "0.1.16"
+version = "0.1.17"
 description = "Serve terminal sessions over the web"
 authors = ["Will McGugan <will@textualize.io>"]
 license = "MIT"
diff --git a/src/textual_webterm/cli.py b/src/textual_webterm/cli.py
index 0c19b8c..615f863 100644
--- a/src/textual_webterm/cli.py
+++ b/src/textual_webterm/cli.py
@@ -149,10 +149,12 @@ def app(
     _config = default_config()
 
     landing_apps: list = []
+    is_compose_mode = False
     if landing_manifest:
         landing_apps = load_landing_yaml(landing_manifest)
     elif compose_manifest:
         landing_apps = load_compose_manifest(compose_manifest)
+        is_compose_mode = True
 
     server = LocalServer(
         "./",
@@ -160,6 +162,7 @@ def app(
         host=host,
         port=port,
         landing_apps=landing_apps,
+        compose_mode=is_compose_mode,
     )
     for app_entry in landing_apps:
         server.add_terminal(app_entry.name, app_entry.command, slug=app_entry.slug)
diff --git a/src/textual_webterm/docker_stats.py b/src/textual_webterm/docker_stats.py
new file mode 100644
index 0000000..2ca23bc
--- /dev/null
+++ b/src/textual_webterm/docker_stats.py
@@ -0,0 +1,240 @@
+"""Docker container CPU stats via Unix socket.
+
+Reads container stats from Docker socket using only asyncio and stdlib.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import contextlib
+import json
+import logging
+import socket
+from collections import deque
+from pathlib import Path
+
+log = logging.getLogger("textual-webterm")
+
+DOCKER_SOCKET = "/var/run/docker.sock"
+STATS_HISTORY_SIZE = 30  # Number of CPU readings to keep
+POLL_INTERVAL = 2.0  # Seconds between polls
+
+
+class DockerStatsCollector:
+    """Collects CPU stats from Docker containers via the Docker socket."""
+
+    def __init__(self, socket_path: str = DOCKER_SOCKET) -> None:
+        self._socket_path = socket_path
+        # container_name -> deque of CPU % values (0-100)
+        self._cpu_history: dict[str, deque[float]] = {}
+        self._running = False
+        self._task: asyncio.Task | None = None
+        # Track previous CPU values for delta calculation
+        self._prev_cpu: dict[str, tuple[int, int]] = {}
+
+    @property
+    def available(self) -> bool:
+        """Check if Docker socket is available."""
+        return Path(self._socket_path).exists()
+
+    def get_cpu_history(self, container_name: str) -> list[float]:
+        """Get CPU history for a container."""
+        if container_name not in self._cpu_history:
+            return []
+        return list(self._cpu_history[container_name])
+
+    async def _make_request(self, path: str) -> dict | None:
+        """Make HTTP request to Docker socket."""
+        loop = asyncio.get_event_loop()
+
+        def _sync_request() -> bytes | None:
+            try:
+                sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+                sock.settimeout(5.0)
+                sock.connect(self._socket_path)
+
+                request = f"GET {path} HTTP/1.1\r\nHost: localhost\r\n\r\n"
+                sock.sendall(request.encode())
+
+                # Read response
+                chunks = []
+                while True:
+                    chunk = sock.recv(4096)
+                    if not chunk:
+                        break
+                    chunks.append(chunk)
+                sock.close()
+                return b"".join(chunks)
+            except (OSError, TimeoutError):
+                return None
+
+        response = await loop.run_in_executor(None, _sync_request)
+        if response is None:
+            return None
+
+        # Parse HTTP response - find JSON body after headers
+        try:
+            response_str = response.decode("utf-8", errors="replace")
+            # Split headers and body
+            if "\r\n\r\n" in response_str:
+                _, body = response_str.split("\r\n\r\n", 1)
+            else:
+                body = response_str
+
+            # Handle chunked encoding - find the JSON object
+            if body.startswith("{"):
+                json_str = body
+            else:
+                # Skip chunk size line in chunked encoding
+                lines = body.split("\r\n")
+                for line in lines:
+                    if line.startswith("{"):
+                        json_str = line
+                        break
+                else:
+                    return None
+
+            return json.loads(json_str)
+        except (json.JSONDecodeError, ValueError):
+            return None
+
+    def _calculate_cpu_percent(
+        self, container: str, cpu_stats: dict, precpu_stats: dict
+    ) -> float | None:
+        """Calculate CPU percentage from stats.
+
+        Formula: (cpu_delta / system_delta) * num_cpus * 100
+        """
+        try:
+            cpu_usage = cpu_stats.get("cpu_usage", {})
+            precpu_usage = precpu_stats.get("cpu_usage", {})
+
+            cpu_total = cpu_usage.get("total_usage", 0)
+            precpu_total = precpu_usage.get("total_usage", 0)
+            system_cpu = cpu_stats.get("system_cpu_usage", 0)
+            presystem_cpu = precpu_stats.get("system_cpu_usage", 0)
+
+            # Use previous values if precpu_stats is empty (first read)
+            if precpu_total == 0 and container in self._prev_cpu:
+                precpu_total, presystem_cpu = self._prev_cpu[container]
+
+            # Store current values for next calculation
+            self._prev_cpu[container] = (cpu_total, system_cpu)
+
+            cpu_delta = cpu_total - precpu_total
+            system_delta = system_cpu - presystem_cpu
+
+            if system_delta <= 0 or cpu_delta < 0:
+                return None
+
+            # Get number of CPUs
+            online_cpus = cpu_stats.get("online_cpus")
+            if online_cpus is None:
+                percpu = cpu_usage.get("percpu_usage", [])
+                online_cpus = len(percpu) if percpu else 1
+
+            cpu_percent = (cpu_delta / system_delta) * online_cpus * 100.0
+            return min(cpu_percent, 100.0 * online_cpus)  # Cap at max possible
+
+        except (KeyError, TypeError, ZeroDivisionError):
+            return None
+
+    async def _poll_container(self, container_name: str) -> None:
+        """Poll stats for a single container."""
+        # Docker API uses container name without leading slash
+        path = f"/containers/{container_name}/stats?stream=false"
+        stats = await self._make_request(path)
+
+        if stats is None:
+            return
+
+        cpu_stats = stats.get("cpu_stats", {})
+        precpu_stats = stats.get("precpu_stats", {})
+
+        cpu_percent = self._calculate_cpu_percent(container_name, cpu_stats, precpu_stats)
+        if cpu_percent is not None:
+            if container_name not in self._cpu_history:
+                self._cpu_history[container_name] = deque(maxlen=STATS_HISTORY_SIZE)
+            self._cpu_history[container_name].append(cpu_percent)
+
+    async def _poll_loop(self, containers: list[str]) -> None:
+        """Background polling loop."""
+        while self._running:
+            for container in containers:
+                if not self._running:
+                    break
+                try:
+                    await self._poll_container(container)
+                except Exception:
+                    log.debug("Error polling stats for %s", container)
+            await asyncio.sleep(POLL_INTERVAL)
+
+    def start(self, containers: list[str]) -> None:
+        """Start collecting stats for given containers."""
+        if not self.available:
+            log.debug("Docker socket not available at %s", self._socket_path)
+            return
+
+        if self._running:
+            return
+
+        self._running = True
+        self._task = asyncio.create_task(self._poll_loop(containers))
+        log.info("Started Docker stats collection for %d containers", len(containers))
+
+    async def stop(self) -> None:
+        """Stop collecting stats."""
+        self._running = False
+        if self._task:
+            self._task.cancel()
+            with contextlib.suppress(asyncio.CancelledError):
+                await self._task
+            self._task = None
+
+
+def render_sparkline_svg(
+    values: list[float],
+    width: int = 100,
+    height: int = 20,
+    stroke_color: str = "#4ade80",
+    fill_color: str = "rgba(74, 222, 128, 0.2)",
+) -> str:
+    """Render a list of values as an SVG sparkline.
+
+    Args:
+        values: List of values to plot (0-100 range expected for CPU %)
+        width: SVG width in pixels
+        height: SVG height in pixels
+        stroke_color: Line color
+        fill_color: Fill color under the line
+
+    Returns:
+        SVG string
+    """
+    if not values:
+        # Empty placeholder
+        return f'<svg width="{width}" height="{height}" xmlns="http://www.w3.org/2000/svg"></svg>'
+
+    # Normalize values to 0-1 range
+    max_val = max(values) if max(values) > 0 else 1
+    normalized = [v / max_val for v in values]
+
+    # Calculate points
+    points = []
+    x_step = width / max(len(values) - 1, 1)
+    for i, v in enumerate(normalized):
+        x = i * x_step
+        y = height - (v * (height - 2)) - 1  # Leave 1px margin
+        points.append(f"{x:.1f},{y:.1f}")
+
+    path_line = " ".join(points)
+
+    # Create filled area path (line + close to bottom)
+    fill_points = [*points, f"{width},{height}", f"0,{height}"]
+    path_fill = " ".join(fill_points)
+
+    svg = f'''<svg width="{width}" height="{height}" xmlns="http://www.w3.org/2000/svg">
+  <polygon points="{path_fill}" fill="{fill_color}" />
+  <polyline points="{path_line}" fill="none" stroke="{stroke_color}" stroke-width="1.5" />
+</svg>'''
+    return svg
diff --git a/src/textual_webterm/local_server.py b/src/textual_webterm/local_server.py
index c3cb559..5c755e9 100644
--- a/src/textual_webterm/local_server.py
+++ b/src/textual_webterm/local_server.py
@@ -20,6 +20,7 @@ from rich.style import Style
 from rich.text import Text
 
 from . import constants
+from .docker_stats import DockerStatsCollector, render_sparkline_svg
 from .exit_poller import ExitPoller
 from .identity import generate
 from .poller import Poller
@@ -187,6 +188,7 @@ class LocalServer:
         port: int = 8080,
         exit_on_idle: int = 0,
         landing_apps: list | None = None,
+        compose_mode: bool = False,
     ) -> None:
         self.host = host
         self.port = port
@@ -206,12 +208,16 @@ class LocalServer:
 
         self._websocket_connections: dict[RouteKey, web.WebSocketResponse] = {}
         self._landing_apps = landing_apps or []
+        self._compose_mode = compose_mode
 
         self._screenshot_cache: dict[str, tuple[float, str]] = {}
         self._screenshot_cache_etag: dict[str, str] = {}
         self._screenshot_locks: dict[str, asyncio.Lock] = {}
         self._route_last_activity: dict[str, float] = {}
 
+        # Docker stats collector (only used in compose mode)
+        self._docker_stats: DockerStatsCollector | None = None
+
     @property
     def app_count(self) -> int:
         return len(self.session_manager.apps)
@@ -291,6 +297,7 @@ class LocalServer:
         routes: list[web.AbstractRouteDef] = [
             web.get("/ws/{route_key}", self._handle_websocket),
             web.get("/screenshot.svg", self._handle_screenshot),
+            web.get("/cpu-sparkline.svg", self._handle_cpu_sparkline),
             web.get("/health", self._handle_health_check),
             web.get("/", self._handle_root),
         ]
@@ -324,6 +331,14 @@ class LocalServer:
             await runner.setup()
             stack.push_async_callback(runner.cleanup)
 
+            # Start Docker stats collector in compose mode
+            if self._compose_mode and self._landing_apps:
+                self._docker_stats = DockerStatsCollector()
+                if self._docker_stats.available:
+                    containers = [app.slug for app in self._landing_apps]
+                    self._docker_stats.start(containers)
+                    stack.push_async_callback(self._docker_stats.stop)
+
             site = web.TCPSite(runner, self.host, self.port)
             await site.start()
 
@@ -613,6 +628,34 @@ class LocalServer:
             headers = {"Cache-Control": "no-cache", "ETag": etag}
             return web.Response(text=svg, content_type="image/svg+xml", headers=headers)
 
+    async def _handle_cpu_sparkline(self, request: web.Request) -> web.Response:
+        """Return CPU sparkline SVG for a container."""
+        container = request.query.get("container", "")
+        if not container:
+            raise web.HTTPBadRequest(text="Missing container parameter")
+
+        # Get dimensions from query params
+        try:
+            width = int(request.query.get("width", "100"))
+        except ValueError:
+            width = 100
+        width = max(50, min(300, width))
+
+        try:
+            height = int(request.query.get("height", "20"))
+        except ValueError:
+            height = 20
+        height = max(10, min(100, height))
+
+        # Get CPU history
+        values: list[float] = []
+        if self._docker_stats:
+            values = self._docker_stats.get_cpu_history(container)
+
+        svg = render_sparkline_svg(values, width=width, height=height)
+        headers = {"Cache-Control": "no-cache, max-age=0"}
+        return web.Response(text=svg, content_type="image/svg+xml", headers=headers)
+
     async def _handle_health_check(self, _request: web.Request) -> web.Response:
         return web.Response(text="Local server is running")
 
@@ -665,6 +708,7 @@ class LocalServer:
                 for app in self._landing_apps
             ]
             tiles_json = json.dumps(tiles)
+            compose_mode_js = "true" if self._compose_mode else "false"
             html_content = f"""<!DOCTYPE html>
 <html>
 <head>
@@ -674,7 +718,9 @@ class LocalServer:
         h1 {{ margin-bottom: 8px; }}
         .grid {{ display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 12px; }}
         .tile {{ background: #1e293b; border: 1px solid #334155; border-radius: 8px; overflow: hidden; box-shadow: 0 2px 6px rgba(0,0,0,0.4); }}
-        .tile-header {{ padding: 10px 12px; font-weight: bold; border-bottom: 1px solid #334155; display: flex; align-items: center; gap: 8px; }}
+        .tile-header {{ padding: 10px 12px; font-weight: bold; border-bottom: 1px solid #334155; display: flex; align-items: center; justify-content: space-between; }}
+        .tile-title {{ display: flex; align-items: center; gap: 8px; }}
+        .sparkline {{ opacity: 0.9; }}
         .tile-body {{ padding: 0; }}
         .thumb {{ width: 100%; height: 180px; object-fit: contain; background: #0b1220; display: block; }}
         .meta {{ padding: 8px 12px; color: #94a3b8; font-size: 12px; }}
@@ -686,12 +732,25 @@ class LocalServer:
     <div class=\"grid\" id=\"grid\"></div>
     <script>
         const tiles = {tiles_json};
+        const composeMode = {compose_mode_js};
         function makeTile(tile) {{
             const card = document.createElement('div');
             card.className = 'tile';
             const header = document.createElement('div');
             header.className = 'tile-header';
-            header.innerHTML = `<span>${{tile.name}}</span>`;
+            const titleSpan = document.createElement('div');
+            titleSpan.className = 'tile-title';
+            titleSpan.innerHTML = `<span>${{tile.name}}</span>`;
+            header.appendChild(titleSpan);
+            if (composeMode) {{
+                const sparkline = document.createElement('img');
+                sparkline.className = 'sparkline';
+                sparkline.width = 80;
+                sparkline.height = 16;
+                sparkline.alt = 'CPU';
+                header.appendChild(sparkline);
+                card.sparkline = sparkline;
+            }}
             const body = document.createElement('div');
             body.className = 'tile-body';
             const img = document.createElement('img');
@@ -719,6 +778,9 @@ class LocalServer:
                 const tile = tiles[cards.indexOf(card)];
                 const url = `/screenshot.svg?route_key=${{encodeURIComponent(tile.slug)}}`;
                 card.img.src = url;
+                if (composeMode && card.sparkline) {{
+                    card.sparkline.src = `/cpu-sparkline.svg?container=${{encodeURIComponent(tile.slug)}}&width=80&height=16&_t=${{Date.now()}}`;
+                }}
             }}
         }}
 
diff --git a/tests/test_docker_stats.py b/tests/test_docker_stats.py
new file mode 100644
index 0000000..6873e85
--- /dev/null
+++ b/tests/test_docker_stats.py
@@ -0,0 +1,209 @@
+"""Tests for docker_stats module."""
+
+import pytest
+from unittest.mock import MagicMock, patch, AsyncMock
+from textual_webterm.docker_stats import (
+    DockerStatsCollector,
+    render_sparkline_svg,
+    STATS_HISTORY_SIZE,
+)
+
+
+class TestRenderSparklineSvg:
+    """Tests for SVG sparkline rendering."""
+
+    def test_empty_values(self):
+        """Empty values produce empty SVG."""
+        svg = render_sparkline_svg([])
+        assert "<svg" in svg
+        assert "width=" in svg
+        assert "polygon" not in svg  # No data to draw
+
+    def test_single_value(self):
+        """Single value renders correctly."""
+        svg = render_sparkline_svg([50.0])
+        assert "<svg" in svg
+        assert "polygon" in svg
+        assert "polyline" in svg
+
+    def test_multiple_values(self):
+        """Multiple values render as sparkline."""
+        values = [10.0, 50.0, 30.0, 80.0, 20.0]
+        svg = render_sparkline_svg(values)
+        assert "<svg" in svg
+        assert "polygon" in svg
+        assert "polyline" in svg
+
+    def test_custom_dimensions(self):
+        """Custom width/height are applied."""
+        svg = render_sparkline_svg([50.0], width=200, height=40)
+        assert 'width="200"' in svg
+        assert 'height="40"' in svg
+
+    def test_custom_colors(self):
+        """Custom colors are applied."""
+        svg = render_sparkline_svg(
+            [50.0],
+            stroke_color="#ff0000",
+            fill_color="rgba(255, 0, 0, 0.3)",
+        )
+        assert "#ff0000" in svg
+        assert "rgba(255, 0, 0, 0.3)" in svg
+
+    def test_zero_values(self):
+        """All zero values don't cause division errors."""
+        svg = render_sparkline_svg([0.0, 0.0, 0.0])
+        assert "<svg" in svg
+
+    def test_high_values(self):
+        """High CPU values (100%+) render correctly."""
+        svg = render_sparkline_svg([100.0, 150.0, 200.0])
+        assert "<svg" in svg
+
+
+class TestDockerStatsCollector:
+    """Tests for Docker stats collector."""
+
+    def test_available_checks_socket(self, tmp_path):
+        """available property checks socket existence."""
+        socket_path = tmp_path / "docker.sock"
+        collector = DockerStatsCollector(str(socket_path))
+        assert collector.available is False
+
+        socket_path.touch()
+        assert collector.available is True
+
+    def test_get_cpu_history_empty(self):
+        """Empty history returns empty list."""
+        collector = DockerStatsCollector("/nonexistent")
+        assert collector.get_cpu_history("container1") == []
+
+    def test_get_cpu_history_with_data(self):
+        """CPU history returns stored values."""
+        collector = DockerStatsCollector("/nonexistent")
+        collector._cpu_history["test"] = [10.0, 20.0, 30.0]
+        # get_cpu_history converts deque to list
+        collector._cpu_history["test"] = list.__new__(list)
+        collector._cpu_history["test"].extend([10.0, 20.0, 30.0])
+
+        history = collector.get_cpu_history("test")
+        assert history == [10.0, 20.0, 30.0]
+
+    def test_calculate_cpu_percent(self):
+        """CPU percentage calculation."""
+        collector = DockerStatsCollector("/nonexistent")
+
+        cpu_stats = {
+            "cpu_usage": {"total_usage": 1000000000},
+            "system_cpu_usage": 10000000000,
+            "online_cpus": 4,
+        }
+        precpu_stats = {
+            "cpu_usage": {"total_usage": 500000000},
+            "system_cpu_usage": 5000000000,
+        }
+
+        result = collector._calculate_cpu_percent("test", cpu_stats, precpu_stats)
+        assert result is not None
+        assert 0 <= result <= 400  # 4 CPUs max
+
+    def test_calculate_cpu_percent_zero_delta(self):
+        """Zero system delta returns None."""
+        collector = DockerStatsCollector("/nonexistent")
+
+        cpu_stats = {
+            "cpu_usage": {"total_usage": 1000},
+            "system_cpu_usage": 1000,
+            "online_cpus": 1,
+        }
+        precpu_stats = {
+            "cpu_usage": {"total_usage": 1000},
+            "system_cpu_usage": 1000,
+        }
+
+        result = collector._calculate_cpu_percent("test", cpu_stats, precpu_stats)
+        assert result is None
+
+    def test_start_without_socket(self, tmp_path):
+        """Start does nothing if socket not available."""
+        collector = DockerStatsCollector(str(tmp_path / "nonexistent.sock"))
+        collector.start(["container1"])
+        assert collector._running is False
+        assert collector._task is None
+
+    @pytest.mark.asyncio
+    async def test_stop_without_start(self):
+        """Stop is safe to call without start."""
+        collector = DockerStatsCollector("/nonexistent")
+        await collector.stop()  # Should not raise
+
+    @pytest.mark.asyncio
+    async def test_make_request_no_socket(self):
+        """Request returns None if socket unavailable."""
+        collector = DockerStatsCollector("/nonexistent")
+        result = await collector._make_request("/test")
+        assert result is None
+
+    def test_cpu_history_max_size(self):
+        """CPU history respects max size."""
+        from collections import deque
+
+        collector = DockerStatsCollector("/nonexistent")
+        collector._cpu_history["test"] = deque(maxlen=STATS_HISTORY_SIZE)
+
+        # Add more than max entries
+        for i in range(STATS_HISTORY_SIZE + 10):
+            collector._cpu_history["test"].append(float(i))
+
+        assert len(collector._cpu_history["test"]) == STATS_HISTORY_SIZE
+
+
+class TestLocalServerSparklineEndpoint:
+    """Tests for the CPU sparkline endpoint in LocalServer."""
+
+    @pytest.mark.asyncio
+    async def test_sparkline_endpoint_missing_container(self):
+        """Missing container param returns 400."""
+        from aiohttp.web import HTTPBadRequest
+        from textual_webterm.local_server import LocalServer
+        from textual_webterm.config import Config
+
+        server = LocalServer("./", Config(), compose_mode=True)
+
+        request = MagicMock()
+        request.query = {}
+
+        with pytest.raises(HTTPBadRequest):
+            await server._handle_cpu_sparkline(request)
+
+    @pytest.mark.asyncio
+    async def test_sparkline_endpoint_returns_svg(self):
+        """Sparkline endpoint returns SVG."""
+        from textual_webterm.local_server import LocalServer
+        from textual_webterm.config import Config
+
+        server = LocalServer("./", Config(), compose_mode=True)
+
+        request = MagicMock()
+        request.query = {"container": "test", "width": "80", "height": "20"}
+
+        response = await server._handle_cpu_sparkline(request)
+        assert response.content_type == "image/svg+xml"
+        assert "<svg" in response.text
+
+    @pytest.mark.asyncio
+    async def test_sparkline_with_stats_collector(self):
+        """Sparkline uses stats collector data when available."""
+        from textual_webterm.local_server import LocalServer
+        from textual_webterm.config import Config
+
+        server = LocalServer("./", Config(), compose_mode=True)
+        server._docker_stats = MagicMock()
+        server._docker_stats.get_cpu_history.return_value = [10.0, 20.0, 30.0]
+
+        request = MagicMock()
+        request.query = {"container": "test"}
+
+        response = await server._handle_cpu_sparkline(request)
+        server._docker_stats.get_cpu_history.assert_called_once_with("test")
+        assert "<svg" in response.text