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