Python Unit Testing | FastAPI with Pytest Tutorial (fast & easy)

Everybody wants maintainable and scalable  software but they don't want to put in the   extra work to make sure that it's tested so  bugs don't get introduced and a fun fact 87   of applications don't have unit tests at all  so to separate you from the other 87 which   will put you in the top of 13 is to implement  unit tests in your application that will allow   your application to be secure and allow you to  be able to add enhancements quickly and make   your application scalable maintainable and have  less bugs so in this video I'm going to show you   how to implement Pytest and https to be able to  test against client requests and unit tests in   Python so let's dive into the video alright so  in this video we are going to be able to write   tests for our FastAPI application so just like  we always do the very first thing we're going   to do is create a virtual environment by doing  python3 Dash MV EnV EnV now this will create a   virtual environment for our application where I'm  going to say source and V slash bin slash activate   and now we need to install our dependency so  we can say pip install FastAPI and uvicorn once you do that this will install all  the dependencies that we need for our   FastAPI application to work correctly so these  yellow lines will go away here momentarily but   in our main.pi application we have our FastAPI  application where we have a to do of name and   completed we have a fake mock database that's  going to store all of our to-do's and then we   can get the list of the to Do's create a new to do  get a specific to do based on the ID update a to   do and delete a to do so if we went ahead and ran  this application enter Swagger documentation we'd   be able to run all of these API endpoints but for  the Simplicity of this video let's just go right   into how we can test and Implement testing for  FastAPI now the very first thing that we need to   install is HTTP X and this is a way for us to be  able to use a client request to be able to test   our API endpoints so let's go ahead and import  this and now what we need to do is install Pytest   and Pytest is unit testing for Apple location  so we're going to be able to test in unit test   our python code as well as our API endpoints  so let's go ahead and say pip install Pytest   now that we have all four dependencies  which is FastAPI uvicorn Pytest and httpx   let's go ahead and say new file and here we  want to name this test underscore main.pi   and the naming convention is this is it's going to  start with tests that's how you know it's a test   file and then underscore and then main which is  the file that we're testing against dot Pi so when   we run our Pytest it's going to look for these  test files now the very first thing that we need   to do here is just say from fastapi.testclient  import our test client and then from our DOT main   import our apps and our to-do's now unlike where  we do main app equals FastAPI we want to grab the   app which is FastAPI from our main and import it  into our test client so we can then go ahead and   say client equals test client where we pass in  our app we then want to set up a function that   just deletes all of to-do's so in this case  it's going to delete all the to-do's from our   application even though it's just a blank list so  you probably want to set up some kind of sqlite   external database that will be able to run against  this but as of right now we'll just say def setup function brackets and then inside here  I'm just going to say to Do's dot clear all right so what this does this is before  each test we are just going to delete all   of the to-do's so they don't touch each other  so one test doesn't influence another test all   right now the very first thing I'm going to say  here is Def test read to Do's response which is   our response from our client which is our test  client dot get and we're just verifying using   assert and assertions are like true and false  to see if it's true or not our response code   is going to be a 200 when we call just our normal  get and then we also are expecting an empty list   so if we go back here we look at our git  we can see that it's going to return all   of the to Do's values and it's going to  return a status code of 200 but because to   Do's list is empty it should just return  an empty list and a status code of 200. and we can go ahead and run this just by typing  in Pytest and immediately we can see that we had   one test that was passed we have two warnings  just because it's using some deprecated files   but outside of that we have our test passing  now if for whatever reason your application   is crashing right here because it can't find the  main functionality just close vs code and reopen   it sometimes it gets lost when you're creating new  files all right so now that we've done that let's   create another test for creating a to-do where  we can just right under here go ahead and just   say def test create to do where we're creating  our response is equal to client.post so we're   checking our post functionality we're making  sure our Json has a key of name with a value of   buy groceries we're making sure it's completed and  false and then we want to verify that we get a 200   response back after passing this in and that the  response is just going to be the exact same thing   so if we come over here and we look at our post  functionality we can see that we just add a new   to do to our list and here we are verifying that  once we add it we can test against it so let's go   ahead and just say Pytest and see that now both  of our tests have passed now if we throw another   S at the end novel sudden our test does not pass  so if we said Pytest we can see that we get a fail   and if we scroll up we can see that it's going to  throw an assertion error now this is going to be   assert completed of groceries equals completed  groceries so we can see that it does not equal   the groceries and it'll tell you right here so the  differing items is named by groceries is not equal   to named up by groceries with an extra s so let's  go ahead and just change this back to just 1s   so our application passes we now want to go  ahead and test our read to do of a single ID   so we can do this by right under here saying  def test read to do with our client dot post of   just an empty slash Json equals Name by groceries  completed equals false response equals client dot   get slash one so we're passing in one as the path  parameter and again we're just verifying that this   is going to equal this so when we add a new item  you know we're going to be adding a primary key   of one and we're just verifying that hey that's  inside and I don't think we're actually passing in   a primary key I think it's going to be the first  item in the list so if we say Pytest we can see   that now all three of our tests pass let's now  go ahead and verify against a post for an update   and right here let's go ahead and say test dot  update where we're saying client dot put request   which we're going to be doing client.post and  this just sets up our client call and then we   can do client dot put right here where we're  updating our buy groceries to buy vegetables   after we already added in there so now we go  ahead and say Pytest we can see that we have   all four tests passed and then lastly we can do  the exact same assertions for our delete to do so   if we come over here now we say def test delete  to do we pass in our client of buy groceries we   are then trying to delete that ID or the first  element of our list making sure that we get a   status code of 200 and then buy groceries is  actually gone within the response so now if we   go ahead and say Pytest we can see that we get all  five tests passing and this is essentially how you   can use Pytest and our test client from FastAPI  to a be able to use assertions to test the unit   tests and test the value of the Python business  logic and then also we can use the response in   clients to test and validate the API endpoints  for our FastAPI application if you're able to   find Value go ahead and click like if you found  value in this video go ahead and like the video   and go ahead and check out one other FastAPI video  from my playlist and I will see you in the next

Channel: Eric Roby

Views: 10,754

Keywords: python, unit testing, python unit test, pytest, pytest tutorial, pytest example, pytest setup, pytest for beginners, getting started with pytest, pytest framework in python, fastapi, fastapi unit testing, fastapi pytest, fastapi tutorial, fastapi python, fastapi python tutorial, python fastapi, fastapi tutorial for beginners, fastapi rest api, python api

Id: jM-zWp8dNQA

Length: 9min 4sec (544 seconds)

Published: Fri Oct 06 2023