From f7ccc18cdd3696a29483e31bfea2f7afbbd7e857 Mon Sep 17 00:00:00 2001
From: Sawyer Cutler <sawyer@dirtroad.dev>
Date: Fri, 21 Aug 2026 00:15:01 -0700
Subject: [PATCH] Fix Linux CI platform-detection flake in activatable-row
 tests

isMacPlatform() reads navigator.platform, which happy-dom's
GlobalRegistrator reports as whatever the host OS is - Darwin-flavored
on a Mac, something else on Linux CI. The "ctrl-click on Mac" tests
inherited that host value instead of controlling it, so they passed
locally on macOS but failed identically on ubuntu-latest.

Each test now stubs navigator.platform to the value it means to
exercise (matching the existing navigator.clipboard stub pattern in
library-page-selection.test.tsx), so both the Mac and non-Mac branches
of isAdditiveSelectClick are asserted deterministically on any OS. No
production code changes - isMacPlatform's behavior was already correct.
---
 apps/web/src/activatable-row.test.ts          | 29 +++++++++++++++++--
 apps/web/test/library-page-selection.test.tsx |  8 +++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/apps/web/src/activatable-row.test.ts b/apps/web/src/activatable-row.test.ts
index 47aabf4e7..95bd78af1 100644
--- a/apps/web/src/activatable-row.test.ts
+++ b/apps/web/src/activatable-row.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, test } from "bun:test";
+import { afterEach, describe, expect, test } from "bun:test";
 
 import {
   isAdditiveSelectClick,
@@ -6,18 +6,43 @@ import {
   rowActivationProps,
 } from "./activatable-row";
 
+// `isAdditiveSelectClick`'s Mac/non-Mac branch reads `navigator.platform`,
+// which happy-dom's `GlobalRegistrator` reports as whatever the *host* OS
+// is — Darwin-flavored on a Mac, something else on Linux CI. Each test
+// below pins the platform it means to exercise instead of inheriting the
+// host's, so both branches are deterministic on any OS.
+const originalPlatform = Object.getOwnPropertyDescriptor(navigator, "platform");
+
+function stubPlatform(platform: string): void {
+  Object.defineProperty(navigator, "platform", {
+    configurable: true,
+    value: platform,
+  });
+}
+
+afterEach(() => {
+  if (originalPlatform !== undefined) {
+    Object.defineProperty(navigator, "platform", originalPlatform);
+  }
+});
+
 describe("isAdditiveSelectClick", () => {
-  // The test DOM reports a Darwin platform, so these exercise the Mac rules.
   test("cmd-click is additive", () => {
     expect(isAdditiveSelectClick({ metaKey: true, ctrlKey: false })).toBe(true);
   });
 
   test("ctrl-click is not additive on Mac (it's the context-menu gesture)", () => {
+    stubPlatform("MacIntel");
     expect(isAdditiveSelectClick({ metaKey: false, ctrlKey: true })).toBe(
       false,
     );
   });
 
+  test("ctrl-click is additive on non-Mac", () => {
+    stubPlatform("Linux x86_64");
+    expect(isAdditiveSelectClick({ metaKey: false, ctrlKey: true })).toBe(true);
+  });
+
   test("a plain click is not additive", () => {
     expect(isAdditiveSelectClick({ metaKey: false, ctrlKey: false })).toBe(
       false,
diff --git a/apps/web/test/library-page-selection.test.tsx b/apps/web/test/library-page-selection.test.tsx
index e7b36f0fe..242c713e2 100644
--- a/apps/web/test/library-page-selection.test.tsx
+++ b/apps/web/test/library-page-selection.test.tsx
@@ -52,6 +52,14 @@ beforeEach(() => {
     configurable: true,
     value: { writeText: mock(() => Promise.resolve()) },
   });
+  // isAdditiveSelectClick's Mac/non-Mac branch reads navigator.platform,
+  // which happy-dom reports as whatever the host OS is — Darwin-flavored
+  // locally, something else on Linux CI. Pinned here so the ctrl-click
+  // test below exercises the Mac branch deterministically on any OS.
+  Object.defineProperty(navigator, "platform", {
+    configurable: true,
+    value: "MacIntel",
+  });
   toastMock.mockClear();
 });