Add failing test case for .watch(file)

README.md

@@ -239,9 +239,9 @@ Efficiently mirror this drive into another. Returns a [`MirrorDrive`](https://gi
 
 Call `await mirror.done()` to wait for the mirroring to finish.
 
-#### `const watcher = db.watch([folder])`
+#### `const watcher = db.watch([file|folder])`
 
-Returns an iterator that listens on `folder` to yield changes, by default on `/`.
+Returns an iterator that listens on a `file` or `folder` to yield changes, by default on `/`.
 
 Usage example:
 ```js

test.js

@@ -462,6 +462,23 @@ test('watch(folder) should normalize folder', async function (t) {
   onchange = null
 })
 
+test('watch(file) basic', async function (t) {
+  t.plan(1)
+  t.timeout(1000)
+
+  const { drive } = await testenv(t.teardown)
+  const buf = b4a.from('hi')
+
+  await drive.put('/a.txt', buf)
+
+  const watcher = drive.watch('/a.txt')
+  watcher.next().then(data => {
+    t.ok(data)
+  })
+
+  await drive.put('/a.txt', buf)
+})
+
 test('drive.diff(length)', async (t) => {
   const { drive, paths: { root, tmp } } = await testenv(t.teardown)
   const paths = []