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In this video, we're going to look at JUnits Assertions

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API, which it gives us to get a bit of a feel for the

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kinds of assertions which we can do in our code.

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So let's jump in. So

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picking up from where we were in the

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last video, if we just get rid of that now,

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since we're talking about assertions, I should

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dig into these a little bit further.

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So JUnit has an assert class.

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So if I type Assert and then ., you

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can see here there are a ton of different methods

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which enable you to assert different things, courtesy

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of JUnits Assertions API.

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So in general you can assert things, but you

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can also fail tests like we've seen before.

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But focusing on the assertion side, you

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can assert that things are not null.

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So in other words, like an object reference

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is present in a variable. So it's useful

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for example, if you call a method and

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you expect an object to be returned, you

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might want to check that it's not null.

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You can check that some boolean condition is true.

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You can check that two arrays are equal. You can

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see here they're overloaded for different types

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pointing the two objects are equal, and again

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they are overloaded methods, so you can feel

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free to check those out in your own time.

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But just note that in general, these methods tend to

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come in pairs, so you can have assertEquals,

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and then there'll be an assertNotEquals, or there's

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an assertTrue, then there's an assertFalse.

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And broadly, what these allow you to check

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for, are basically (not clear) of object references.

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Equality of objects and values. Actually

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speaking of equality as well, you'll notice here that

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we have the first argument is the expected thing that

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we expect, and the second argument is the actual object

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that we get back, which we'll see in a second.

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We also have assertions of as many equal

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to and that kind of thing.

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So the best thing to do now is to look

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into your project, which you have set up in the

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previous section, and just do what I did. Just do

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Assert. after you've imported the org.junit.assert

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class and just go through those methods and really

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take them in and have a bit of a play around and

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get a feel for how they work.

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And in this way you get to know them

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first hand as you get to use them.