Add unit tests for renderer pixel ratio calculation, including Safari specific capping logic

tests/unit/renderer-pixel-ratio.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  isSafariUserAgent,
+  resolveRendererPixelRatio
+} from "../../src/rendering/renderer-pixel-ratio";
+
+describe("renderer pixel ratio", () => {
+  it("caps Safari renderer pixel ratio more aggressively", () => {
+    const safariUserAgent =
+      "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Safari/605.1.15";
+
+    expect(isSafariUserAgent(safariUserAgent)).toBe(true);
+    expect(
+      resolveRendererPixelRatio({
+        devicePixelRatio: 2,
+        userAgent: safariUserAgent
+      })
+    ).toBe(1);
+  });
+
+  it("keeps the existing non-Safari high-DPI cap", () => {
+    const chromeUserAgent =
+      "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36";
+
+    expect(isSafariUserAgent(chromeUserAgent)).toBe(false);
+    expect(
+      resolveRendererPixelRatio({
+        devicePixelRatio: 3,
+        userAgent: chromeUserAgent
+      })
+    ).toBe(2);
+  });
+});