Quantitative Assertions

[MUSIC] 0:00 All testing libraries work on the idea of assertions. 0:04 Some call them behaviors, or descriptions, 0:08 and assertions test a condition in your code that must be met. 0:10 For example, 0:14 when creating a car object, you could test that the new object has a model name. 0:14 If it doesn't, the assertion fails and we found an error in our code. 0:19 In Python's unit test framework, we have quite a few assertions that let you 0:22 test different conditions, like if two values are equal, an object is 0:25 an instance of a certain class, or if a certain exception is raised by some code. 0:29 I'll link to the full list of assertions in the teacher's notes but 0:34 we'll look at the most important ones in this video and the next couple. 0:37 So, let's get started. 0:40 So, we've already looked at the assert keyword. 0:42 But the unit test framework, 0:45 unit test module, gives us a bunch of other assertions that we can use. 0:47 We don't just have to assert that a statement is true. 0:51 So, let's test the four methods in our move class using these assertions. 0:55 So, the first one probably the easiest one is the equality test. 1:00 So we wanna test the dunder eq and 1:08 the dunder ne, which is for equal and not equal methods. 1:12 But like I said we don't wanna test them directly. 1:16 So let's say test equal. 1:17 And your methods do have to start with test. 1:20 If your methods don't start with test they won't be run as tests. 1:23 So we're gonna say rock1 is equal to rock, oops, sorry, 1:26 we need to make that moves.Rock. 1:30 And rock2 is equal to moves.rock. 1:33 And we're gonna say self.assertequal rock1 and rock2. 1:36 And then let's test the not equal. 1:43 Test_not_equal and self and we'll say rock1 or 1:48 rock is equal to moves.Rock and 1:53 we'll say paper is equal to moves.Paper, and 1:57 then self.assertNotEqual, and rock and paper, 2:01 because rock and paper should not be equal to each other. 2:07 But rock and rock, should be. 2:14 This should handle this testing. 2:15 We, we're making the two rock instances. 2:17 We make sure they're equal to each other and then make a rock instance and 2:19 a paper instance and make sure that they are not equal to each other. 2:22 We're repeating ourselves a little bit with making all of these rocks, 2:25 but we'll clean that up later. 2:28 So let's try running these tests. 2:30 So, python tests.py, and, oop, let's make this a little taller. 2:31 There we go. 2:39 Let's just run it again. 2:41 There we go. 2:43 So, it ran four tests. 2:44 One, two, three, four. 2:45 And they all passed. 2:46 So, great. Four tests, four passes. 2:48 So now, let's dry up our test a little bit. 2:50 We can add a method to our test case, and 2:53 I'll leave this up at the top that is named setUp. 2:55 And this is one of the fun cases where a library predates PEP 8. 3:01 So setUp has camel case, PEP 8 says we should be lowercase with underscores but 3:05 it's old, so it stays just like it is. 3:11 Okay, so this function, this method will get called, 3:14 will get run before each of our tests. 3:19 So, any code we put in here will always have like, kinda a fresh state. 3:21 So what we're gonna do is say, self.rock is equal to 3:26 moves.Rock, self.paper is equal to moves.Paper, 3:31 and self.scissors is equal to moves.Scissors. 3:36 And now I wish I had written something about Jagger, 3:41 because then I would have had moves.Jagger. 3:44 Okay. 3:47 Now Python has to do a little bit more work here. 3:48 Python has to instantiate these variables every time. 3:49 But we get to write less code and really that's what's important, right? 3:52 Our workload? 3:55 Okay. 3:57 So we have these three attributes. 3:58 We have self.rock, self.paper, self.scissors. 3:59 Let's use them. 4:02 So here we're gonna do rock one. 4:03 We don't need rock one, we don't need rock one at all. 4:05 And we don't even need rock two. 4:08 So we're gonna take those out. 4:09 And we're gonna assert that self.rock is equal to a new rock instance. 4:11 And then here we can take these two out completely and 4:19 just assert that self.rock is not equal to self.paper, 'kay? 4:23 So, we've dried the stuff up a whole lot. 4:30 Now, we have to make the new rock instance here, 4:32 because we don't want to just test that the object is equal to itself. 4:34 We know the object is equal to itself. 4:37 We wanna make sure the object is equal to another instance of the same class, 4:39 because two rocks with the same, this should be tied. 4:43 So we save all that, we run our tests again, and 4:46 oh, I have a typo, this should be moves.Rock. 4:51 All right, one more time? 4:54 And we're all good. 4:57 All the tests are still passing. 4:59 Okay, to complete the testing of all of our moves, 5:00 we should test our greater than, or the dunder vt, and 5:04 our less than, or the dunder le methods. 5:09 So, let's test that rock is better than scissors, because it should be. 5:13 So, self.assertGreater, 5:21 self.rock, and self.scissors. 5:24 And let's also test that paper is worse than scissors. 5:29 So, self.assertLess, 5:37 self.paper, and self.scissors. 5:41 Okay. 5:46 So, we're trying to write these in a, a fairly human readable way. 5:47 So let's, let's test this. 5:52 All of our tests pass, and that's great. 5:55 Now, there are a lot more search engines that are available. 5:57 We're gonna cover a few more in the course, and 5:59 the rest I'm gonna make sure and link to in the teacher's notes. 6:01 So, be able to read those and you'll be able to test all sorts of things. 6:04 Assertions that deal with quantitative values like assertEqual or 6:08 assertGreater are really handy when you're dealing with numbers. 6:11 I know that I use them quite a bit, both in regular scripts and for 6:14 testing web apps. 6:18 Or I wanna make sure that a status code is 200, 304, 404, or something else. 6:19 Remember, you have the full power of Python too, so feel free to use len and 6:24 other functions in your assertions. 6:29