From abef4e29b8e20ed6a5116ee909eb0ba0e1028bb2 Mon Sep 17 00:00:00 2001
From: Sergey Kozyrenko <sirozha_blr@tut.by>
Date: Wed, 22 Jul 2026 05:58:24 +0700
Subject: [PATCH] test(e2e): fail the contrast probe on an unparseable colour
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paint() set fillStyle to black, then to the requested colour — but an
unparseable colour is a silent no-op on fillStyle, leaving black, which measures
as a spurious ~21:1 pass. Assign the colour against two different sentinels and
throw when it doesn't land on the same value, so a broken colour surfaces the
gate instead of clearing it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 frontend/e2e/helpers/contrast.ts | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/frontend/e2e/helpers/contrast.ts b/frontend/e2e/helpers/contrast.ts
index 28ab7a76..2723c087 100644
--- a/frontend/e2e/helpers/contrast.ts
+++ b/frontend/e2e/helpers/contrast.ts
@@ -100,8 +100,21 @@ export const measureContrast = async (page: Page, probe: string): Promise<number
             context.clearRect(0, 0, 1, 1);
 
             for (const layer of layers) {
+                // An unparseable colour is a silent no-op on fillStyle, leaving the previous
+                // value — which measures as a spurious ~21:1 pass. Assign it against two
+                // different sentinels: a colour that applied lands on the same value both
+                // times, an invalid one keeps whichever sentinel preceded it.
                 context.fillStyle = '#000000';
                 context.fillStyle = layer;
+                const fromBlack = context.fillStyle;
+
+                context.fillStyle = '#ffffff';
+                context.fillStyle = layer;
+
+                if (context.fillStyle !== fromBlack) {
+                    throw new Error(`contrast: colour "${layer}" did not apply`);
+                }
+
                 context.fillRect(0, 0, 1, 1);
             }