Hello, everybody.

My name is Colton Ogden.

This is CS50 on Twitch.

And I'm joined by Kareem Zidane.

KAREEM ZIDANE: Hello, everyone.

COLTON OGDEN: So, Kareem and I did a stream about--

was it last week or two weeks ago?

KAREEM ZIDANE: Yep.

COLTON OGDEN: On GitHub and git where we talked about what is GitHub,

how do you actually use it and use it on your local machine?

How do you then tie that into our repository on GitHub?

Which is sort of the first part of the equation

for a lot of modern development.

But what are we going to talk about today that sort of extends that?

KAREEM ZIDANE: Today we are going to talk about two very important concepts

or terms in the dev ops world, namely continuous integration

and continuous deployment, otherwise known as CI/CD.

And just because of the context, we are also

going to be talking about a little bit of testing techniques.

COLTON OGDEN: Sure, yeah, very important things.

You know, obviously as you're developing applications

beyond just toy applications, getting into actually a business setting--

KAREEM ZIDANE: Yeah.

COLTON OGDEN: --or even CS50 type--

a lot of CS50's apps and infrastructure is all sort of

based around this idea of continuously deploying testing and integrating

your apps onto their respective platforms.

KAREEM ZIDANE: That's true.

Yeah, so last time we actually talked about GitHub, as you mentioned.

And we talked about the idea that these tools

are very, very useful because we developers tend

to make changes all the time.

And so, it's nice to keep track of these changes

and be able to toggle between or switch between them later on.

Today, we're going to extend that by means

of being able to ensure that our changes don't break our projects or anything

that we have in our project already.

And we're also going to be able to automatically maybe publish our project

or deploy our project to several targets.

If it's a website, for example, we can deploy this to Amazon, or to Heroku,

or if it's a Python package we can deploy this to Pipeline, and so on.

COLTON OGDEN: Yeah, because obviously if we're deploying our website,

we make changes and we push them.

We want to make sure that they don't break.

KAREEM ZIDANE: True.

COLTON OGDEN: The irony being that Facebook is currently at 503.

KAREEM ZIDANE: Yes.

COLTON OGDEN: Which we just saw earlier.

So, let's see what we have in the chat today.

We have a few people in the chat.

We have a ForkDB, which I'm not sure if we saw you before in a previous stream.

[? RahulNogBelecuras ?] is a regular.

[? SashaCan't32 ?] says hello.

MKloppenburg says "hey, everybody."

MKloppenberg is a regular.

And [? MajordFought ?] says, "hi, what is this session about?"

This session's going to be about CI-CD.

So, what's the first big topic that we want to bite off today?

KAREEM ZIDANE: OK, do you want to switch to my--

COLTON OGDEN: Yeah, let's do that.

So, let's bring up Kareem's screen here.

KAREEM ZIDANE: All right.

So, here's my terminal.

And I'm going to start by writing my own sort of simple math library that

has one function.

And this function is going to test if an integer, a number, a positive integer,

or non-negative integer, is prime or not.

COLTON OGDEN: OK.

KAREEM ZIDANE: And if you don't recall, a prime number

is a number that's only divisible by itself and 1 only.

So yeah, let's try to get started.

So, I'm going to open a new file here.

Call it MyMathLib.pi.

COLTON OGDEN: OK.

KAREEM ZIDANE: And I'm going to define a Python function called

Is_Prime that takes in one argument, n.

And then inside of that function, what I'm going to do

is try to check if a number is prime or not.

Now, mathematically, if a number is not prime,

it has to have a factor that's less than or equal to it square root.

COLTON OGDEN: OK.

KAREEM ZIDANE: Right?

So, I mean, you should probably trust me on that.

But the mathematical proof for this is pretty simple.

We're not really going to go through it right now.

COLTON OGDEN: Yeah, you can't define something by something

larger than half of itself, right?

KAREEM ZIDANE: You can divide something by something--

COLTON OGDEN: That's why we take the square root, because we can't find

a factor that's larger than its half.

KAREEM ZIDANE: OK.

I'm going to--

OK, I'm not sure I get that totally.

But I'm going to trust you on this as well.

COLTON OGDEN: That's the way I understand it.

KAREEM ZIDANE: All right, I mean, yeah, sure.

So, we can we can start by iterating through the numbers from i

up to n, including the square root of n, which

is the number that we're trying to figure out if it's prime or not here.

COLTON OGDEN: So, from 1 until half of--

so, say 20-- it would be not half the square root in that case.

It would be like--

KAREEM ZIDANE: Yep.

COLTON OGDEN: 4.0-something.

KAREEM ZIDANE: That's why I was puzzled when you said half of half.

COLTON OGDEN: Yeah.

Because there is another algorithm I thought where are they

checked up to half of it.

But I guess the square root makes sense.

KAREEM ZIDANE: Right.

So, we better not divide by 0.

We better not divide by 1.

So, we're going to start by dividing by 2

and then go up to the square root of n, which I

believe is going to be in math, right?

Import math.

COLTON OGDEN: Yeah, I think so.

KAREEM ZIDANE: I mean, we're going to figure this out if it doesn't work.

So, square root of--

COLTON OGDEN: We got a couple messages in the chat, too.

It says, [? RahulNog. ?] I can't properly

stream because there's some buffering problem.

Maybe network poor on 1080p?

Yeah, possibly.

Try, if there is an option, try downgrading grading the quality.

ForDB says, "I'm here for the first time."

And [? RahulNog, ?] they're there for the first time as well.

So, thanks so much for joining us for the first time.

KAREEM ZIDANE: Yeah.

COLTON OGDEN: As we dive into CI/CD.

Definitely check out our prior streams in the GitHub stream if curious.

[? Nuanda333, ?] [? Asley, ?] says, "oh, that is so cool.

Kareem the dream.

We have a game between my friends to guess if the number is prime or not.

Next time I will cheat using this."

Yeah, definitely the cheat-y way to go.

KAREEM ZIDANE: All right, sounds great.

Yeah, all right.

So, let's move on.

So now we're looping through the numbers starting

with 2 up to and including, presumably, the square root of n, in this case.

And what we're going to do is check if n is divisible by i, in which case

n remainder i is going to be equal to 0.

In this case, we're going to return false, right?

COLTON OGDEN: Mhm.

KAREEM ZIDANE: Otherwise return true.

How does that sound to you?

COLTON OGDEN: Sounds good.

KAREEM ZIDANE: All right.

So, let's actually test this out.

How would you test this out?

COLTON OGDEN: I'd probably run it on a sequence of numbers

that I've predetermined have a certain--

a certain set of numbers that I know are prime versus a set of numbers

that I know are not prime.

KAREEM ZIDANE: Exactly.

So, I just fired up a Python interpreter here.

I'm going to import my function.

So from MyMathLib, import is prime.

Now I have is_prime in scope.

So, I'm just going to try to call in a bunch of numbers.

So for example, 0--

whoa, OK.

What's happening here?

COLTON OGDEN: So, is_prime.

Float object cannot be interpreted as an integer.

KAREEM ZIDANE: That's probably because the square root

function returns a float.

And this expects an integer.

COLTON OGDEN: Oh, yeah.

KAREEM ZIDANE: So, let's do this.

Let's switch it to an integer.

OK, let's try it again.

Import is prime from y--

the other way around.

From MyMathLib.

Import is_prime.

And then try again, is_prime of 0.

True.

That's weird.

COLTON OGDEN: OK, interesting.

KAREEM ZIDANE: OK.

COLTON OGDEN: So, did we not special case a 0, perhaps?

KAREEM ZIDANE: Yeah, there seems to be a problem here.

Well, it's saying that 0 is the prime, 1 is prime, 2 his prime, 3 is prime,

4, 5, OK, is 4 prime?

Well, it seems to be buggy.

So, the first thing that we-- it's a good practice.

The first thing that we should do when we find a bug like this in our program

is actually pinpoint this bug.

Or in other words--

you know, you can you can imagine, every time I

do something or try to fix a bug around a feature

that I open up a Python interpreter like this and keep trying things like this.

This is not really very time-efficient.

Because I'm going to be doing this again and again.

And this seems to be like a computer's problem.

Right?

COLTON OGDEN: So, you can maybe do what you just

did in the loop, or something in a script,

and just read your program over a bunch of them?

KAREEM ZIDANE: That's true.

COLTON OGDEN: Instead of manually typing them out, maybe.

KAREEM ZIDANE: Yeah, I could I could definitely

write a program that would test these automatically for me.

Luckily though, Python has actually a testing framework called Unit Test.

COLTON OGDEN: Oh, nice.

KAREEM ZIDANE: That we could actually use.

So, this stream is not really about Unit Test itself.

But we're going to be exploring a bit of its features.

Hopefully we'll explain the ones that we use while we're going through them so

that they're clear to everyone.

So, let's actually try this.

So, in another file.

I'm going to call tests.py.

All I need to do to use Unite Test is import UnitTests, like this.

And then create a class called--

I'm going to call it, in this case, to try to be descriptive,

IsPrimeTests because I'm testing my [? s ?] prime function.

And this class is going to extend UnitTest.TestCase.

And by extend, this is actually an object-oriented programming concept.

It basically means use features from the class UnitTest.testCase,

COLTON OGDEN: You're basically making a new class

called IsPrimeTests, which takes all of the behavior of test case,

in this case.

KAREEM ZIDANE: Correct, it's exactly that, yeah.

It's based on UnitTest.TestCase in this case, which is another class defined

in the unit test library.

COLTON OGDEN: [INAUDIBLE] says that my audio is a little low.

I just changed the sensitivity.

Is it still a little bit too low?

It does look like the audio levels are a bit low on it.

Hold on, let me try--

whoops.

Is that any better?

Are we getting a little bit-- we're getting a little bit closer.

I'm not sure why it's so low.

Test, one, two, three.

Sorry, my mic says it's at a good sensitivity level.

I'm not sure.

How's that?

Is that any better?

Oh, now it's in the red.

OK, cool, cool.