diff --git a/js/tests/tell-me-how-many_test.mjs b/js/tests/tell-me-how-many_test.mjs
new file mode 100644
index 000000000..a0c02c6fd
--- /dev/null
+++ b/js/tests/tell-me-how-many_test.mjs
@@ -0,0 +1,70 @@
+import * as cp from 'child_process'
+import fs from 'fs/promises'
+import { join, resolve, isAbsolute } from 'path'
+import { tmpdir } from 'os'
+import { promisify } from 'util'
+const mkdir = fs.mkdir
+const rmdir = fs.rmdir
+const writeFile = fs.writeFile
+
+const exec = promisify(cp.exec)
+
+export const tests = []
+export const setup = async () => {
+  const randomFilesNumber = Math.floor(Math.random() * (30 - 1) + 1)
+  const dir = tmpdir()
+
+  // check if already exists and rm?
+  await mkdir(`${dir}/random`)
+  for (let i = 0; i < randomFilesNumber; i++) {
+    await writeFile(`${dir}/random/${i}.txt`, '', 'utf8')
+  }
+
+  return { randomFilesNumber, tmpPath: dir }
+}
+const countDirLength = async ({ dirLength, arg, ctx, path, eq }) => {
+  const scriptPath = join(resolve(), path)
+  const { stdout } = await exec(`node ${scriptPath} ${arg}`, {
+    cwd: arg ? `${ctx.tmpPath}` : `${ctx.tmpPath}/random`,
+  })
+
+  // await rmdir(`${ctx.tmpPath}/random`, { recursive: true })
+  return eq(Number(stdout.trim()), dirLength)
+}
+
+tests.push(async ({ path, eq, ctx }) => {
+  // will execute the script with "random" as an argument
+  // `random` folder has a random file number
+  return countDirLength({
+    path,
+    eq,
+    ctx,
+    arg: 'random',
+    dirLength: ctx.randomFilesNumber,
+  })
+})
+
+tests.push(async ({ path, eq, ctx }) => {
+  // will execute the script without argument
+  // in the `random` folder
+  return countDirLength({
+    path,
+    eq,
+    ctx,
+    arg: '',
+    dirLength: ctx.randomFilesNumber,
+  })
+})
+
+tests.push(async ({ path, eq, ctx }) => {
+  // will execute the script with `random` folder's absolute path as argument
+  return countDirLength({
+    path,
+    eq,
+    ctx,
+    arg: `${ctx.tmpPath}/random`,
+    dirLength: ctx.randomFilesNumber,
+  })
+})
+
+Object.freeze(tests)
diff --git a/subjects/tell-me-how-many/README.md b/subjects/tell-me-how-many/README.md
new file mode 100644
index 000000000..2c136be96
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+++ b/subjects/tell-me-how-many/README.md
@@ -0,0 +1,33 @@
+## tell-me-how-many
+
+### Instructions
+
+Your very special partner's birthday is coming soon. So you've decided to organise a very special party. Invitations has been sent for a while... and good news: answers are back. We didn't count it, you've been too generous. But we saved every one of them as a file in a special folder for you. Have fun!
+
+Create a `tell-me-how-many.mjs` script that:
+- takes a relative or absolute folder path as argument from the command line
+- read this directory path
+- get the number of entries in this folder
+- print the result in console
+
+### Notions
+
+- [Node file system: `readdir`](https://nodejs.org/api/fs.html#fs_fspromises_readdir_path_options)
+- [Node path: `isAbsolute`](https://nodejs.org/api/path.html#path_path_isabsolute_path)
+
+<!-- + check if is directory ?? -->
+- [Node stat](https://nodejs.org/docs/latest/api/fs.html#fs_fspromises_stat_path_options)
+- [Node stat: `isDirectory`](https://nodejs.org/docs/latest/api/fs.html#fs_stats_isdirectory)
+<!--
+  again?
+- [Node process: `argv`](https://nodejs.org/docs/latest/api/process.html#process_process_argv)
+- [Node path: `resolve`](https://nodejs.org/api/path.html#path_path_resolve_paths)
+- [Node path: `join`](https://nodejs.org/api/path.html#path_path_join_paths)
+-->
+
+
+### Provided files
+
+Download [`tell-me-how-many.zip`](https://assets.01-edu.org/tell-me-how-many) to have at your disposal the `guests` folder containing the files to count in your script. You must save it in your `tell-me-how-many` exercise folder to test your script on it.
+
+