00:00 Right, before diving into writing

00:02 tests for that program,

00:04 let's just quickly look at

00:05 how to write a test

00:06 with pytest in the first place,

00:07 and how to run it from the command line.

00:11 And first of all I want to contrast

00:13 it with unittest,

00:14 which is in the standard library.

00:16 So here at left you have a super simple program,

00:20 it's almost ridiculous.

00:21 But it's Hello name, takes a name

00:24 and just returns the hello name string.

00:27 And look at the amount of code you

00:28 have to write in unittest to get a test

00:31 for that running.

00:33 Because it's class-based,

00:34 so you have to subclass another class,

00:37 write a function,

00:38 and use a self.assert notation

00:41 so let's show that next.

00:53 Alright, so import unittest,

00:55 import the program,

00:56 make a class,

00:58 inherit from unittest test case,

01:01 write a method, which needs to start with test

01:03 to be recognized as a valid test,

01:06 use self.assert equal notation,

01:09 call the function,

01:10 and check for hard coded output.

01:13 If the files run as a main script,

01:15 call the main method on unittest.

01:18 Right, and it works.

01:22 And it fills if I change the return,

01:24 and that's good,

01:26 and notice that pytest can run unittest code,

01:31 so pytest can be run from the command line,

01:34 without any switches,

01:36 if you'll look for files that start with test,

01:38 and run the methods or functions in there

01:41 that start with test.

01:43 So that means that I can even

01:46 leave out this main block

01:47 and it should still work.

01:51 Right, but here comes the first benefit

01:54 of pytest is that you can write

01:55 test code in a much shorter way.

01:57 I don't need unittest, I don't need the class,

02:00 I can just define functions.

02:02 They do need to start with test,

02:03 and instead of the self.assert equal,

02:07 I can just use the classic assert.

02:12 And this should work.

02:14 It does not.

02:15 Self is still in the program

02:16 because it was still in the function.

02:22 Same output.

02:23 Make it fail,

02:27 and here is the second advantage of pytest.

02:30 The output is much nicer.

02:36 unittest was definitely not bad,

02:39 but pytest,

02:40 especially if you go into

02:41 more complex operations and errors,

02:44 it's a great debugging tool.

02:47 So look at that. Instead of what was it?

02:52 Oh that doesn't count

02:53 one two three, well it was

02:54 still short because this is

02:55 an easy program,

02:56 but you can already see that

02:58 this is way cleaner.

03:06 So that's the simplest

03:07 of pytest programs

03:08 and I just wanted to show you

03:10 how it differs from unittest and

03:12 how you can run it from the command line.

03:14 Just the basic steps to get you

03:15 up and running.