README has no run steps or CLI example (#177)

README.md

@@ -19,6 +19,25 @@ transfers.
 Bun, TypeScript, Hono, `bun:sqlite`. No build step for the web page
 (`public/index.html` is served as-is).
 
+## Run it
+
+```sh
+bun install
+bun run dev
+```
+
+`bun run dev` serves the web page and API on http://localhost:3200 (set
+`PORT` to use another port). Demo data is seeded into `splitbill.sqlite`
+on first run.
+
+The CLI reads the same database:
+
+```sh
+bun run src/cli.ts groups
+bun run src/cli.ts balances <group>
+bun run src/cli.ts export <group>
+```
+
 ## Layout
 
 ```

tests/readme.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, test } from "bun:test";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+const root = join(import.meta.dir, "..");
+const readme = readFileSync(join(root, "README.md"), "utf8");
+const pkg = JSON.parse(readFileSync(join(root, "package.json"), "utf8"));
+const server = readFileSync(join(root, "src/server.ts"), "utf8");
+const cli = readFileSync(join(root, "src/cli.ts"), "utf8");
+
+function runItSection(): string {
+  const start = readme.indexOf("\n## Run it\n");
+  if (start === -1) return "";
+  const rest = readme.slice(start + 1);
+  const next = rest.indexOf("\n## ", 1);
+  return next === -1 ? rest : rest.slice(0, next);
+}
+
+describe("README Run it", () => {
+  test("Run it section lists install, dev and URL", () => {
+    const section = runItSection();
+    expect(section).not.toBe("");
+    expect(section).toContain("bun install");
+    expect(section).toContain("bun run dev");
+    expect(section).toContain("http://localhost:3200");
+  });
+
+  test("Run it section has a CLI example", () => {
+    expect(runItSection()).toContain("bun run src/cli.ts groups");
+    expect(readme).toContain("balances <group>");
+    expect(readme).toContain("export <group>");
+    expect(cli).toContain("splitbill balances <group-id>");
+    expect(cli).toContain("splitbill export <group-id>");
+  });
+
+  test("Run it commands match package.json and server default port", () => {
+    expect(pkg.scripts.dev).toBe("bun run src/server.ts");
+    expect(server).toContain("process.env.PORT ?? 3200");
+  });
+});