fix testing

Author: fabridamicelli

book/10_testing.ipynb

@@ -54,7 +54,6 @@
     "**Refactoring**  \n",
     "When we want to modify working code, since tests can give us some degree of confidence that we are not breaking the functionality, for example, while optimizing running time.\n",
     "\n",
-    "\n",
     "**Documentation**  \n",
     "Tests can serve as a way to communicate other people (our ourselves) the expected behaviour of our code."
    ]
@@ -129,7 +128,13 @@
     "    return value * value\n",
     "```\n",
     "\n",
-    "So let's create a directory (next to `src`) called `tests` and make a file called `tests/test_square.py` including our previous `test_square` code:\n",
+    "So let's create a directory (next to `src`) called `tests` and make a file called `tests/test_square.py` including our previous `test_square` code.\n",
+    "\n",
+    "If you've been following along, your project should look more or less like this:\n",
+    "\n",
+    "![](./images/tree-3.png){width=150}\n",
+    "\n",
+    "Now put this content in `test_square.py`:\n",
     "\n",
     "```python\n",
     "from pycourse.square import square  # Import function from source code test\n",
@@ -141,9 +146,9 @@
     "    assert square(5) == 25\n",
     "```\n",
     "\n",
-    "Notice that we do not call the function, we just define it.\n",
     "\n",
     ":::{.callout-important}\n",
+    "Notice that we do not call the function, we just define it.\n",
     "The file must be called `test_*.py` or `*_test.py` for pytest to discover it and the unit tests must start with `test_`.\n",
     ":::\n",
     "\n",
@@ -250,7 +255,7 @@
    "source": [
     "## Exercises\n",
     "1) Modify the function `square` in `square.py` so that it returns `value * value * 2` and run the test again. Pay close attention to the error messages and the diffs!\n",
-    "2) Write a function called `reverse_str` that takes a string and returns the reversed version, eg \"hola\" -> \"aloh\". Write a unit test and make sure the tests pass. Think about covering corner cases in your tests.S\n",
+    "2) Write a function called `reverse_str` that takes a string and returns the reversed version, eg \"hola\" -> \"aloh\". Write a unit test and make sure the tests pass. Think about covering corner cases in your tests.\n",
     "3) Make the function `reverse_str` strict to only accept strings as input and throw an error if another type is passed. Write a unit test that covers both the \"happy path\" and the \"error path\"."
    ]
   }