1
00:00:00,180 --> 00:00:02,880
So the problem with computerFire and

2
00:00:02,880 --> 00:00:07,200
computerPlaceShip is that they
have random outcomes built in.

3
00:00:07,200 --> 00:00:10,320
Each of these functions really
does two different things.

4
00:00:10,320 --> 00:00:15,580
First they build a random location,
then they do something with that location,

5
00:00:15,580 --> 00:00:18,200
like fire a shot or place a ship.

6
00:00:19,600 --> 00:00:23,630
In programming, we call this tight
coupling when two distinct functions

7
00:00:23,630 --> 00:00:26,960
are bundled up so that they can
only really be used together.

8
00:00:26,960 --> 00:00:30,730
Now a hallmark of tightly coupled code
is that it makes our job of writing unit

9
00:00:30,730 --> 00:00:32,310
tests harder.

10
00:00:32,310 --> 00:00:34,940
So to refactor this code I
think we can actually just

11
00:00:34,940 --> 00:00:37,250
abstract those two ideas apart.

12
00:00:37,250 --> 00:00:41,290
We see that the same code appears
in both the computerFire and

13
00:00:41,290 --> 00:00:43,220
computerPlaceShip functions,

14
00:00:43,220 --> 00:00:47,480
the part that generates two numbers in
the board range and puts them in an array.

15
00:00:47,480 --> 00:00:51,810
So we can pull that out into its own
function that returns the result.

16
00:00:51,810 --> 00:00:54,040
Let's call the function
getRandomCoordinates.

17
00:01:06,540 --> 00:01:10,872
Then I'll cut the variable declarations
for x, y, and coordinates out of

18
00:01:10,872 --> 00:01:15,230
the computerFire function and
paste them inside getRandomCoordinates.

19
00:01:16,370 --> 00:01:19,993
So now to put the x and
y numbers in an array,

20
00:01:19,993 --> 00:01:25,250
instead of var coordinates = x,
y, we'll say return x, y.

21
00:01:26,950 --> 00:01:29,930
So now I can delete these from
computerPlaceShip as well.

22
00:01:34,790 --> 00:01:40,790
So, computerPlayShip also randomly
chooses horizontal or vertical.

23
00:01:40,790 --> 00:01:44,910
So we can use the same strategy by pulling
out that logic into a separate function.

24
00:01:46,170 --> 00:01:48,485
Let's call this function
getRandomDirection.

25
00:01:56,451 --> 00:02:01,023
So now I'll go ahead and
cut the direction declaration out of

26
00:02:01,023 --> 00:02:05,785
computerPlaceShip and
paste it inside getRandomDirection.

27
00:02:07,940 --> 00:02:12,668
And in this function instead
of var direction equals =

28
00:02:12,668 --> 00:02:18,061
Math.random, we'll say return Math.random.

29
00:02:18,061 --> 00:02:22,884
So at this point there's actually
nothing left of our original

30
00:02:22,884 --> 00:02:26,640
functions besides a call to fire and
placeShip.

31
00:02:26,640 --> 00:02:30,820
So, at the bottom of our file we can
remove the module that exports for

32
00:02:30,820 --> 00:02:33,280
computerPlaceShip and computerFire.

33
00:02:35,701 --> 00:02:39,552
But now we can also use the randomizers
with the existing fire and

34
00:02:39,552 --> 00:02:43,629
placeShip functions in place of
the original computer functions.

35
00:02:51,710 --> 00:02:55,303
So for example,
we can set up the game to call fire and

36
00:02:55,303 --> 00:03:01,208
placeShip with some attempted random
coordinates in-between human player turns.

37
00:03:01,208 --> 00:03:02,318
Like this.

38
00:03:15,531 --> 00:03:18,988
We also get to use these randomizer
functions in other parts of our game

39
00:03:18,988 --> 00:03:20,450
engine if we need to.

40
00:03:20,450 --> 00:03:21,700
That's a big plus.

41
00:03:21,700 --> 00:03:24,020
More reusable code will
save us time later.

42
00:03:26,530 --> 00:03:29,220
And this way we don't have
to add any tests at all.

43
00:03:29,220 --> 00:03:31,880
In fact, this is another thing
that writing tests helps us with.

44
00:03:33,710 --> 00:03:36,007
When it's hard to write tests for
something,

45
00:03:36,007 --> 00:03:40,060
you might wonder whether you really
need that function in the first place.

46
00:03:40,060 --> 00:03:43,780
And this way, writing tests can
guide us toward simpler code.

47
00:03:43,780 --> 00:03:46,690
We still can't do a super
meaningful test for

48
00:03:46,690 --> 00:03:49,430
the randomizer functions
because of their random nature.

49
00:03:49,430 --> 00:03:54,460
But we've pulled the random pieces apart
from our other application code so

50
00:03:54,460 --> 00:03:56,620
that our other parts remain testable.

51
00:03:56,620 --> 00:04:00,175
Thinking about good unit test
has improved our code yet again,

52
00:04:00,175 --> 00:04:02,336
making it more reusable and modular.

53
00:04:15,425 --> 00:04:17,310
We've learned a lot in this stage.

54
00:04:17,310 --> 00:04:20,100
Set up and tear down in our test suites,
testing for

55
00:04:20,100 --> 00:04:23,870
edge cases, and
keeping our code decoupled and testable.

56
00:04:23,870 --> 00:04:28,020
So you're ready to use Mocha and Chai
to keep doing BDD in your applications.

57
00:04:29,050 --> 00:04:32,990
In the last stage, I'll show you some
other convenient ways to display your test

58
00:04:32,990 --> 00:04:35,960
results and introduce some more
advanced features of Mocha.