Add unit tests and PR test workflow

.github/workflows/test.yml

@@ -0,0 +1,27 @@
+name: Tests
+
+on:
+  pull_request:
+
+jobs:
+  unit-tests:
+    name: Unit tests
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+
+      - name: Lint
+        run: bun run lint
+
+      - name: Test
+        run: bun run test

package.json

@@ -6,7 +6,8 @@
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "eslint"
+    "lint": "eslint",
+    "test": "bun test"
   },
   "dependencies": {
     "@tailwindcss/typography": "^0.5.19",

src/lib/posts.test.ts

@@ -0,0 +1,41 @@
+import { describe, expect, test } from "bun:test";
+
+import { getAllPostIds, getPostData, getSortedPostsData } from "./posts";
+
+describe("getSortedPostsData", () => {
+  test("reads post frontmatter sorted by newest date first", () => {
+    expect(getSortedPostsData()).toEqual([
+      {
+        id: "hello-world",
+        title: "Hello, world",
+        date: "2024-01-01",
+        description: "A short introduction.",
+      },
+    ]);
+  });
+});
+
+describe("getAllPostIds", () => {
+  test("returns route params for markdown posts", () => {
+    expect(getAllPostIds()).toEqual([
+      {
+        params: {
+          slug: "hello-world",
+        },
+      },
+    ]);
+  });
+});
+
+describe("getPostData", () => {
+  test("returns frontmatter and rendered markdown content", async () => {
+    await expect(getPostData("hello-world")).resolves.toMatchObject({
+      id: "hello-world",
+      title: "Hello, world",
+      date: "2024-01-01",
+      description: "A short introduction.",
+      contentHtml:
+        "<p>Welcome. This is the first entry \u2014 more soon on engineering, debate, and building Cursor.</p>\n",
+    });
+  });
+});

src/lib/utils.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, test } from "bun:test";
+
+import { cn, formatDate } from "./utils";
+
+describe("cn", () => {
+  test("merges conditional classes", () => {
+    expect(cn("base", false && "hidden", ["flex", "items-center"])).toBe(
+      "base flex items-center",
+    );
+  });
+
+  test("resolves conflicting Tailwind classes", () => {
+    expect(cn("px-2 py-1", "px-4")).toBe("py-1 px-4");
+  });
+});
+
+describe("formatDate", () => {
+  test("formats dates in UTC", () => {
+    expect(formatDate("2024-01-01")).toBe("January 1, 2024");
+  });
+});