diff --git a/exercises/21-factorial/README.es.md b/exercises/21-factorial/README.es.md
index c1391272..f72157ab 100644
--- a/exercises/21-factorial/README.es.md
+++ b/exercises/21-factorial/README.es.md
@@ -2,14 +2,15 @@
 
 ## 📝 Instrucciones
 
-Escribe un programa que puede calcular el factorial de un número dado.
-Los resultados deberían imprimirse en una secuencia separada por coma en una sola línea. Supongamos que se le entrega la siguiente entrada al programa:
+1. Crea una función llamada `factorial`, que reciba un número como parámatro y retorne su valor factorial.
+
+## Ejemplo de entrada:
 
 ```bash
-8
+factorial(8)
 ```
 
-Entonces el resultado debería ser:
+## Ejemplo de salida:
 
 ```bash
 40320
@@ -17,4 +18,4 @@ Entonces el resultado debería ser:
 
 ## 💡 Pistas:
 
-En el caso de una entrada de datos entregada a la cuestión, debería asumirse como una entrada de la consola.
++ Si no sabes qué es un factorial, revisa la información de este link: https://factorial.mx/numero-funcion-factorial
diff --git a/exercises/21-factorial/README.md b/exercises/21-factorial/README.md
index 5847c798..e5224c90 100644
--- a/exercises/21-factorial/README.md
+++ b/exercises/21-factorial/README.md
@@ -1,21 +1,21 @@
 # `21` Factorial
 
-## 📝 Instructions 
+## 📝 Instructions:
 
-Write a program which can compute the factorial of a given numbers.
-The results should be printed in a comma-separated sequence on a single line.
-Suppose the following input is supplied to the program:
+1. Create a function named `factorial` which receives a number as parameter and returns the factorial of the given numbers.
+
+## Example input:
 
 ```bash
-8
+factorial(8)
 ```
 
-Then, the output should be:
+## Example output:
 
 ```bash
 40320
 ```
 
-## 💡Hints:
+## 💡 Hints:
 
-In case of input data being supplied to the question, it should be assumed to be a console input.
\ No newline at end of file
++ If you don't know what a factorial is, you can check it out on this link: https://www.cuemath.com/numbers/factorial/
diff --git a/exercises/21-factorial/app.py b/exercises/21-factorial/app.py
index e666e544..fce62c1d 100644
--- a/exercises/21-factorial/app.py
+++ b/exercises/21-factorial/app.py
@@ -1 +1 @@
-# Your code here
\ No newline at end of file
+# Your code here
diff --git a/exercises/21-factorial/test.py b/exercises/21-factorial/test.py
new file mode 100644
index 00000000..1852dcb4
--- /dev/null
+++ b/exercises/21-factorial/test.py
@@ -0,0 +1,31 @@
+import io, sys, os, re, pytest
+import app
+
+@pytest.mark.it('You should create a function named factorial')
+def test_factorial_exists(app):
+    try:
+        from app import factorial
+        assert factorial 
+    except AttributeError:
+        raise AttributeError("The function 'factorial' should exist on app.py")
+
+@pytest.mark.it('Testing the function factorial with the number 8, it should return 40320')
+def test_factorial_8(app):
+    try:
+        assert app.factorial(8) == 40320
+    except AttributeError:
+        raise AttributeError("The function 'factorial' should return the value 40320")
+
+@pytest.mark.it('Testing the function factorial with the number 3, it should return 6')
+def test_factorial_3(app):
+    try:
+        assert app.factorial(3) == 6
+    except AttributeError:
+        raise AttributeError("The function 'factorial' should return the value 6")
+
+@pytest.mark.it('Testing the function factorial with the number 1, it should return 1')
+def test_factorial_1(app):
+    try:
+        assert app.factorial(1) == 1
+    except AttributeError:
+        raise AttributeError("The function 'factorial' should return the value 1")
\ No newline at end of file