test: add Playwright e2e spec for color-blindness tool

tests/e2e/color-blindness.spec.ts

@@ -0,0 +1,50 @@
+import fs from "node:fs";
+import path from "node:path";
+import { expect, test, uploadTestImage, waitForProcessing } from "./helpers";
+
+test.describe("Color Blindness Simulation tool", () => {
+  test("upload -> simulate -> download cycle", async ({ loggedInPage: page }) => {
+    await page.goto("/color-blindness");
+    await expect(page.getByText("Color Blindness Simulation").first()).toBeVisible();
+
+    await uploadTestImage(page);
+    await expect(page.getByText("Upload from computer")).not.toBeVisible();
+
+    const dropdown = page.locator("#cb-simulation-type");
+    await expect(dropdown).toBeVisible();
+    await expect(dropdown).toHaveValue("deuteranomaly");
+
+    await dropdown.selectOption("protanopia");
+    await expect(dropdown).toHaveValue("protanopia");
+
+    await page.getByTestId("color-blindness-submit").click();
+    await waitForProcessing(page);
+
+    const downloadBtn = page.getByTestId("color-blindness-download");
+    await expect(downloadBtn).toBeVisible({ timeout: 15_000 });
+
+    const downloadPromise = page.waitForEvent("download");
+    await downloadBtn.click();
+    const download = await downloadPromise;
+    expect(download.suggestedFilename()).toBeTruthy();
+
+    const downloadPath = path.join(
+      process.cwd(),
+      "test-results",
+      "download-color-blindness-result",
+    );
+    await download.saveAs(downloadPath);
+    const stat = fs.statSync(downloadPath);
+    expect(stat.size).toBeGreaterThan(0);
+  });
+
+  test("shows type description when selection changes", async ({ loggedInPage: page }) => {
+    await page.goto("/color-blindness");
+    await uploadTestImage(page);
+
+    const dropdown = page.locator("#cb-simulation-type");
+    await dropdown.selectOption("achromatopsia");
+
+    await expect(page.getByText("Complete color blindness", { exact: false })).toBeVisible();
+  });
+});