6.txt

00:00 The second thing I want to test is the guess method.
00:02 It takes a user input and input is not static,
00:06 you can change and it can be random.
00:08 Even worse, when you run this program
00:10 it's waiting at the prompt to get input
00:11 so your test would hang, quickly demo this.
00:17 Let's make a game object, and run it.
00:26 Actually it's not hanging, it's throwing an error,
00:29 pretty soon, reading from standard input
00:31 output is captured, so that's cool.
00:33 And look at the output, it's pretty verbose
00:35 which is a nice feature of pytest.
00:38 But anyway, we definitely don't want to use input
00:40 literally in tests, so I'm going to use patch again.
00:44 And I'm going to patch the built-ins input,
00:50 and this is another way of marking.
00:52 Here I can give it side effects.
00:56 And a list of expected returns in a row.
01:00 Because I'm having all these exceptions here,
01:02 I'm going to give it a bunch of inputs
01:04 to go through all these scenarios and see
01:06 if each scenario throws the value error
01:09 or accepts the guess as a correct one.
01:11 And will also show you how you can check for
01:14 exceptions in pytest which are important
01:17 because raising exceptions is a common Python pattern.
01:21 So what we're doing here is setting up
01:23 a sequence of return values as if input was
01:26 called that many times.
01:28 So it will return a 11, then 12 as a string,
01:31 then bob, then 12,
01:36 then five minus one, 21
01:40 seven and None.
01:43 And those are the values that we're going to work with,
01:45 and you have to give it an argument,
01:47 it can be called anything.
01:49 And now we have some return data from input to work with.
01:52 So I'm making a game, and again,
01:54 the constructor sets defaults
01:56 for all the internal variables,
01:57 so that should be fine,
01:59 and then I can start to make assertions.
02:02 And the first two side effects or returns are good.
02:10 and again I will show you guess,
02:11 so guess goes through getting an input,
02:14 looking for all the bad inputs and raise a value error
02:17 if so, and if it's good it ends up adding
02:19 it to it's internal set which is the underscore guesses,
02:23 and returning the guess.
02:24 So 11 is good,
02:30 12 is a string should be fine
02:33 because that can be converted into a int.
02:36 The second one, bob, is not a number.
02:38 And the way in pytest to check if an exception is raised
02:42 is to use pytest, and you need to import that,
02:48 and do a with pytest.raises,
02:51 the name of the exception and then the statement
02:57 that would trigger that exception.
02:59 So the next return value from input in the row
03:03 is bob's string, if I call guess with that
03:06 it should raise a value error
03:07 and we're telling pytest to check if
03:10 it actually raises that exception.
03:12 And the same is true for the next one with is 12.
03:16 If I guess again, the guess is already in the guesses set
03:20 and the function manually raises a value error.
03:23 I can just copy this and it will be the same.
03:26 So every new call of guess triggers this input statement
03:31 or call, which triggers a new value in the return list.
03:35 So 12 is done, five should be fine.
03:42 Right let's run what we have so far
03:44 because it's a lot of code and see if it works.
03:50 All right that looks good.
03:51 So now let's do the complete list again.
03:55 And after five comes minus one and 21
03:59 which should be two exceptions because
04:00 they are out of range.
04:08 Another good one, and finally None should not be a good one,
04:15 that falls into this one, if not guess
04:17 raise a value error, please enter a number.
04:19 So we wrap up with...
04:24 So that's save, Control + Z, pytest
04:29 you're still happy.
04:30 I mean if it would say...
04:34 Game guess returns None when given None it will fail.
04:41 So we have please enter a number
04:43 so it actually raised a value error,
04:45 and it was not catching that.
04:47 Here I do, and it works.
04:52 So that's how I use mocking to circumvent
04:56 this input function waiting for input.
04:59 I'm going through all these scenarios
05:01 by giving various side effects.
05:03 Next up, validate guess.