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You have completed JavaScript Unit Testing!
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In this video, we’ll continue writing our BDD outline for Battleship. We’ll write new test specs that correctly test when a ship is located at a given coordinate.
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Our check for
ship function is looking good, but
0:00
we've only proven that
it will report a miss.
0:02
It tells us when no ship is located
at our given coordinates, but
0:05
does it also correctly tell us when a ship
is located at or given coordinates?
0:08
Let's write a new spec
that would prove it.
0:13
Okay, so back inside shiptest.js,
I'll just copy my current spec for
0:16
no ship present and
paste a new spec, right below it.
0:21
Then I'll adjust the description and
expectation.
0:26
So this description will say
should correctly report,
0:29
a ship located, at the given coordinates.
0:33
This spec test, whether
the function correctly finds a ship
0:42
that is located at the given location.
0:45
So we should change the argument
we passed, check for
0:49
ship, to match the players
one ship location.
0:51
So I'll change this to 0,0.
0:55
Then I'll adjust the expected
result to be true.
0:58
So now, when I run npn test in the consul,
1:04
the test report assertion error,
expected,undefined to be true.
1:07
Well currently the only timer
function returns something,
1:13
is when no ship is found.
1:17
So maybe we should add a matching
conditional to return true,
1:19
when something is found.
1:23
So in our check for
ship function inside ship methods.J S,
1:26
will say if no ship is present,
Return false.
1:31
Then we'll say else return true.
1:35
All right, so let's run the test again.
1:46
And cool.
1:51
Now it works.
1:52
But so far, we've only tested check for
1:56
ship using a single ship
with a single location.
1:58
So we should expand our test to be sure it
still works when a player has more than
2:03
one ship, and when a ship is located
at more than one coordinate.
2:07
So again, back inside ship test.js.
2:15
I'll copy the spec at the very top and
2:18
paste a new one at the bottom, then
revise my description and expectations.
2:22
So I'll change this description to say
should handle ships located at more than
2:30
one coordinate.
2:35
This spec will test the same
behaviors we've already tested,
2:44
but, with the ship having
multiple locations.
2:48
So, inside locations,
I'll add a new coordinate of 0,1.
2:51
Then I'll create new expectations for
this location, and
2:58
adjust the expected result to be true.
3:01
So, I'll simply copy this expectation,
and paste the new one right above it.
3:03
And this will say expect check for
ship player at 0,1 to be true.
3:08
Now, you normally don't want your unit
test to have more than one expectation,
3:20
because it might be unclear to
someone reading it what the test is
3:25
supposed to proof.
3:28
Now, in this case, since we have
individual unit tests for positive and
3:29
negative checks,
3:33
I'm comfortable using both expectations
in this unit test for brevity.
3:34
In fact, I'll also add an expectation for
the 0,0 location,
3:40
just to make sure we can find both.
3:43
And I'll set the expected
result to be true.
3:49
All right so let's save our file and
run npm test in the console.
3:53
And great that seems good so far.
4:01
So it looks like check for ships doesn't
break when we give it a bigger ship.
4:04
So let's try more than one ship.
4:09
So I'll copy the bottom
spec inside ship_test,
4:12
and paste a new spec right below it.
4:16
And I'll change this spec's description
to should handle checking multiple ships.
4:19
Then I’ll change the expectations.
4:31
But first I’ll just add one ship.
4:33
To the ship's array with new coordinates.
4:35
So I’ll copy the first location and
paste the new one right below that.
4:38
And change the coordinates to 1,
0 and 1, 1.
4:45
Then right about the last expectation,
I'll add two new expectations for
4:52
this new location.
4:56
So I'll copy one of these and
paste it below.
4:58
And for this I'll say expect
(checkForShip(player at 1, 0 .to be true
5:02
and will add another one that says expect
check ForShip player at [1,1] to be true.
5:07
All right so let's save this.
5:13
Go over to the console and run npm test.
5:20
So now our tests finally catch a bug.
5:24
It looks like multiple
ships don't work correctly.
5:27
So the test passes the first expectations,
which look at the first ship in the array.
5:30
But the expectations aimed
at the second ship fail.
5:37
It says assertion error.
5:41
Expected false to be true.
5:43
But we must have made
a mistake with our loop logic.
5:45
Why else would everything work for
the first ship, that first loop, and
5:49
then break during the second?
5:52
So let's take another look at
our checkForShip function.
5:54
And sure enough, I buried one of
the return statements too deep.
6:03
The loop will currently check for
no matches after every ship, so that means
6:08
that if the first ship isn't a match for
the given location, then the function
6:12
returns false right away before getting
to loop again to the next ship.
6:16
So it looks like we need to
reverse this logic a bit.
6:21
We want the function to return false for
6:24
no matches only after it has
checked every single ship.
6:27
So that means it should return false
only after the loop has finished.
6:31
But it should return true
immediately when it finds a match.
6:36
So we can just switch things around
to capture this idea better.
6:40
So we'll say if ship present return true,
and
6:44
I'll delete this else condition.
6:49
Then right before the closing bracket,
we'll say return false.
6:53
All right so let's save this and
go over to the console and run npm test.
6:59
And great,
it looks like the tests all passed now.
7:06
And to be double sure, we can expand the
test suite a bit as a proof of concept.
7:11
So let's add one more ship to
the ship's array with new coordinates.
7:15
So I'll copy one of the locations and
paste the new one at the bottom.
7:19
Then I'll change the coordinates to 2,0,
2,1.
7:26
And I'll add two new coordinates.
7:30
So this one will be 2,2.
7:34
And the next will be 2,3.
7:37
And then I'll go ahead and
add a new expectation.
7:44
That says expect check for
ship for player at 2,3,
7:50
to be true.
7:55
So now if I go over to the council and
run npm test.
7:58
It works great.
8:03
That was a lot of work, so pat yourself
on the back for doing a great job.
8:06
In the next video, we'll keep
adding specs to this test suite and
8:10
expand our game of Battleship.
8:13
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