diff --git a/src/components/custom-metrics/__tests__/custom-metric-chart-color.browser.test.tsx b/src/components/custom-metrics/__tests__/custom-metric-chart-color.browser.test.tsx
deleted file mode 100644
index 64828318a..000000000
--- a/src/components/custom-metrics/__tests__/custom-metric-chart-color.browser.test.tsx
+++ /dev/null
@@ -1,51 +0,0 @@
-import { describe, expect, it } from "vitest";
-
-import { renderWithApp } from "../../../../tests/browser/render";
-import { CustomMetricChart } from "../custom-metric-chart";
-import type { CustomMetricEntryDto } from "../types";
-
-/**
- * The line takes the series colour it is given (the GKI draws in a chart
- * token beside the ketone series) and keeps primary when it is given none,
- * so a custom metric's chart looks as it always has.
- */
-
-const NOW = Date.now();
-const ENTRIES: CustomMetricEntryDto[] = [3, 2, 1].map((daysAgo, i) => ({
-  id: `e${i}`,
-  customMetricId: "",
-  value: 2 + i,
-  unit: "",
-  measuredAt: new Date(NOW - daysAgo * 86_400_000).toISOString(),
-  note: null,
-  createdAt: new Date(NOW).toISOString(),
-}));
-
-async function lineStroke(color?: string): Promise<string | null> {
-  const { screen } = await renderWithApp(
-    <div style={{ width: 600 }}>
-      <CustomMetricChart
-        name="Index"
-        unit=""
-        targetLow={null}
-        targetHigh={null}
-        decimals={1}
-        entries={ENTRIES}
-        {...(color ? { color } : {})}
-      />
-    </div>,
-  );
-  const curve = () => screen.container.querySelector(".recharts-line-curve");
-  await expect.poll(curve).not.toBeNull();
-  return curve()!.getAttribute("stroke");
-}
-
-describe("<CustomMetricChart> series colour", () => {
-  it("draws the line in the colour it is given", async () => {
-    expect(await lineStroke("var(--chart-4)")).toBe("var(--chart-4)");
-  });
-
-  it("keeps primary by default", async () => {
-    expect(await lineStroke()).toBe("var(--primary)");
-  });
-});
diff --git a/src/components/custom-metrics/__tests__/custom-metric-chart-color.test.tsx b/src/components/custom-metrics/__tests__/custom-metric-chart-color.test.tsx
new file mode 100644
index 000000000..023b19597
--- /dev/null
+++ b/src/components/custom-metrics/__tests__/custom-metric-chart-color.test.tsx
@@ -0,0 +1,81 @@
+import type { ReactNode } from "react";
+import { renderToStaticMarkup } from "react-dom/server";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+/**
+ * The line takes the series colour it is given (the GKI draws in a chart
+ * token beside the ketone series) and keeps primary when it is given none,
+ * so a custom metric's chart looks as it always has.
+ */
+
+const lineProps = vi.hoisted(() => [] as Array<Record<string, unknown>>);
+
+vi.mock("recharts", () => {
+  const Pass = ({ children }: { children?: ReactNode }) => <>{children}</>;
+  const Leaf = () => null;
+  return {
+    ResponsiveContainer: Pass,
+    ComposedChart: Pass,
+    CartesianGrid: Leaf,
+    ReferenceArea: Leaf,
+    ReferenceLine: Leaf,
+    Tooltip: Leaf,
+    XAxis: Leaf,
+    YAxis: Leaf,
+    Line: (props: Record<string, unknown>) => {
+      lineProps.push(props);
+      return null;
+    },
+  };
+});
+
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+import { I18nProvider } from "@/lib/i18n/context";
+
+import { CustomMetricChart } from "../custom-metric-chart";
+import type { CustomMetricEntryDto } from "../types";
+
+const NOW = Date.now();
+const ENTRIES: CustomMetricEntryDto[] = [3, 2, 1].map((daysAgo, i) => ({
+  id: `e${i}`,
+  customMetricId: "",
+  value: 2 + i,
+  unit: "",
+  measuredAt: new Date(NOW - daysAgo * 86_400_000).toISOString(),
+  note: null,
+  createdAt: new Date(NOW).toISOString(),
+}));
+
+function lineStroke(color?: string): unknown {
+  renderToStaticMarkup(
+    <QueryClientProvider client={new QueryClient()}>
+      <I18nProvider initialLocale="en">
+        <CustomMetricChart
+          name="Index"
+          unit=""
+          targetLow={null}
+          targetHigh={null}
+          decimals={1}
+          entries={ENTRIES}
+          {...(color ? { color } : {})}
+        />
+      </I18nProvider>
+    </QueryClientProvider>,
+  );
+  return lineProps.at(-1)?.stroke;
+}
+
+beforeEach(() => {
+  lineProps.length = 0;
+});
+
+describe("<CustomMetricChart> series colour", () => {
+  it("draws the line in the colour it is given", () => {
+    expect(lineStroke("var(--chart-4)")).toBe("var(--chart-4)");
+  });
+
+  it("keeps primary by default", () => {
+    expect(lineStroke()).toBe("var(--primary)");
+  });
+});