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The happy path makes sure that code works the way it was intended to work.
[MUSIC]
0:00
Now that we know how to test, it's time
to start looking at the more difficult
0:04
question, and that is what to test.
0:08
Remember, this is the part where we
developers haven't been replaced yet.
0:11
What we've looked at thus far is
what is known as the happy path.
0:16
You should be able to determine what that
path is by asking yourself this question.
0:19
If this code ran correctly,
how would I know?
0:23
I'd like to take a moment to
practice a skill once more.
0:27
Along with all the other parts we
learned in the how to test stage.
0:30
Why don't we take a look at the other
component that we broke out, the chooser?
0:34
Specifically, let's take a look
at the alpha numeric chooser.
0:38
Okay, so we will press the double shift.
0:42
We'll do Shift, Shift and
then I'll start looking for
0:45
alpha, there we go,
AlphaNumericChooser.java, there it is.
0:48
Okay, so
let's go over some key concepts here.
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First off, this extends a class
called AbstractChooser.
0:57
Let's open that up too.
1:01
This might be the first time you've
seen this keyword here, abstract.
1:04
What this means, basically,
is that the class cannot be instantiated.
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You must extend it and
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override some required methods that
are also marked with the abstract keyword.
1:15
See the icon over here?
1:20
This shows who uses the subclass, and
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then down here this shows who
implements each one of these methods.
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So this one is an abstract method.
1:28
Okay, and you'll notice that over
here it doesn't have any definition.
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Just says what it throws.
1:34
But it's abstract,
you must extend and override this.
1:38
Wow, so this class, this abstract class
also has an inner class named Location.
1:41
Inner classes are helpful sometimes to
create classes that depend on certain
1:49
variables in a surrounding class,
or parent class.
1:53
Do you see here how it's using maxRows and
maxColumns from the AbstracChooser class?
1:57
The AbstractChooser takes a maxRows and
a maxColumns and that's the outside class.
2:02
And the inside class here, this location,
uses the maxRows and the maxColumns,
2:06
because it's in the right scope.
2:11
Also look here, the constructor for
Location is protected.
2:13
So no one other than the code in this
package can create a location, only us.
2:18
So you've used something like this before,
remember map.entry in the map interface?
2:24
It looks like all this is
doing is grabbing a row and
2:29
column, validating that it's allowed,
and then returning it.
2:32
It's a pretty dumb object, right?
2:37
Now, you might not have seen any
of these concepts before, and
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I wanted to use them to show you and
reiterate, that doesn't matter.
2:42
You are testing the behavior,
not the implementation, remember?
2:47
We're not gonna test that
all that stuff is true,
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we're just gonna test the behavior.
2:55
So let's just do that, right?
2:56
What is the happy path
that comes out of here?
2:58
Well the public API says one thing,
3:00
It says locationFromInput,
and it returns a location.
3:04
So how about we make sure that
if we choose something valid
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it returns the expected row and
column, sound good?
3:13
So we wanna test the elementation
specifically, so
3:16
let's switch over to
the AlphanumericChooser.
3:19
So see we can mouse over here and
here we'll jump back over there?
3:22
Cool.
3:26
So, let's create a new test over here,
so again that's Cmd+Shift+T or
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Shift+Ctrl+T in Windows.
3:32
And I'm gonna choose Create New Test.
3:34
JUnit four, it's got the right class name,
it's in the right passage.
3:38
This time let's go ahead and
let's make a before method.
3:42
And let's just go ahead and
have it generate this test.
3:44
We're gonna rename it, we know that
it's gonna give us a wrong name.
3:46
So let's go ahead and create that.
3:49
First things first, let's rename that.
3:52
Let's say validInputReturnsProperLocation.
3:54
All right, so
how about in the Before up here
4:03
we have it create the chooser for
us, right?
4:08
So we're gonna say,
chooser= new AlphaNumericChooser.
4:12
And remember that that takes the max
rows as 26 rows for the alphabet,
4:17
we'll just do that.
4:22
And then 10 columns that's
a big vending machine.
4:23
Let's do that.
4:27
And it says can't resolve chooser, so
4:28
let's have it go ahead and
create the field chooser for us.
4:31
Cool, okay, so we've got the arrange
covered in the before method there,
4:35
now let's do the act.
4:39
So let's go ahead and
get one of those locations out right,
4:41
that was that inner class.
4:45
We'll call it loc and we'll use
the chooser that got instantiated and
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we'll say location from input.
4:50
And let's just pass in the input,
we'll pass in B4, and
4:52
now let's assert that we got
the right location back.
4:57
So we want to make sure that
B4 returns the second row,
5:02
right, A, B, and the fourth column.
5:07
So that's array indices 1 and 3, right?
5:10
Okay, so we're really only
testing one behavior, but
5:15
we're probably gonna do it
in two assert statements.
5:18
That's okay because we're
testing the behavior.
5:21
There's two assert statements but
it's the same behavior, right?
5:23
Okay, so let's do an assert,Equals, and
5:26
remember it goes expected and actual.
5:30
So we expect 1 for the row.
5:34
And we expect 2, or sorry,
we expect 3 for the column, right?
5:40
So that's B4.
5:44
Cool, let's test it, awesome.
5:52
Here we can see our new test is showing up
here and it looks like it passed, great.
5:56
It's kinda handy sometimes to
always make sure that it fails too.
6:00
So cool, we can make sure that it fails.
6:06
You know what though?
6:09
Let's think about this,
what if one these assertions,
6:10
one of these two assertions fail?
6:12
It's not gonna be obvious how it failed,
right?
6:13
Let's break it and let's see.
6:16
All right, so
if I say let's change this to 3.
6:17
It's just gonna say that it's an assertion
error and expected 3 but it was 1.
6:24
But it's not clear,
there's two assertions, not clear.
6:28
Is it talking about the row or
is it talking about the column?
6:30
So this is a great use of
the optional message parameter.
6:33
So what should do is you put on
the positive version of what was expected.
6:38
So let's do that, so this would be here,
this would be the proper row and
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put in here, this is the proper column.
6:49
Okay, and then we refresh and run again,
and we'll see that it says proper row.
6:54
So now, somebody, if this test fails,
7:01
they'll know, because of that message
that we put in there, what that is.
7:02
It's a nice touch, right?
7:06
Fix that back.
7:08
There, now we know what's going on.
7:12
There are definitely more descriptive
assertion patterns that we can use, and
7:13
are available to us, and we'll touch
all those briefly here in a bit.
7:17
Looking at these class,
if we come back here to this class,
7:21
there are some exceptions
that are thrown in here.
7:24
We should probably try to test those too.
7:27
What a happy path we've found.
7:30
Exceptions are also
part of the happy path.
7:32
So after this quick break,
7:34
let's learn how to properly test all
expectations of our public facing API.
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