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Data Persistence with Room

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Saving a Pizza's Toppings

5:16 with Ben Deitch

In this video we'll see how to save which Toppings belong on which Pizza into the PizzaTopping table!

We've just tested our ability to save a pizza. 0:00
But what about saving its toppings? 0:03
Let's add some space at the bottom of the class and 0:06
add a function to help test saving data to the pizza topping table. 0:08
Let's start by adding the @Test annotation, and 0:14
then declaring our test function. 0:18
Fun, and let's call it pizzaToppingTest. 0:20
Just like our other test, we'll want to start by getting access to our 0:25
database and then clearing all the tables. 0:29
Since we already have access to our database and the pizzaTest function, 0:32
let's start by moving the appContext and 0:36
db variables out of the pizzaTest function and into the class itself. 0:39
Then, back in pizzaToppingTest, let's add a call to 0:50
db.clearAllTables, and get on with writing our test. 0:54
We'll need to insert a row for each topping on our pizza. 0:59
So let's call testToppingIds.forEach and then for 1:04
each topping, let's create a new pizza topping 1:08
object combining our testPizzaId with the toppingId. 1:12
So val pizzaTopping is going to equal a new pizza 1:17
topping object where we'll pass in testPizza.id and it. 1:23
Remember that it represents the topping ID we're currently looping on. 1:31
Once we've got the pizza topping, let's insert it with a call to 1:41
db.pizzaToppingDao.insert while passing in the pizza topping. 1:45
Now that we've inserted the data, 1:53
we need to test that we can retrieve which toppings belong to which pizza. 1:55
Let's add a new line at the bottom of the function and 2:01
then create a new val called returnedToppingIDs. 2:04
And let's set it equal to 2:08
db.pizzaToppingDao.getToppingIdsForPizzaId and 2:11
pass in testPizza.Id for the id. 2:18
Then we just need to assert that these are the same topping ids 2:23
from our test topping ids list. 2:26
Let's type assertEquals, and then for the expected value, 2:29
let's pass in test ToppingIds, and for the result let's pass in returnedToppingIds. 2:34
Awesome, that takes care of that test. 2:41
Let's click over here on the left to run it and see how we're doing. 2:44
Oops, looks like we have a foreign key error. 2:58
Thanks to our foreign key constraints, we're not allowed to insert any pizzas or 3:01
toppings that don't exist into our pizza topping table. 3:06
So before we insert any pizza toppings, we'll need to make sure we've already 3:10
inserted the pizzas and toppings into their respective tables. 3:15
To help us rewrite our test, let's break it out into the three sections we learned 3:21
about in the testing course, arrange, act and assert. 3:25
To arrange the test, we'll clear all the tables in the database. 3:30
Then for the Act section, we'll do all the inserting and retrieving of data. 3:36
And for the Assert section, we'll have the Assert. 3:43
Now, to finish the test, we just need to add inserting the pizza and 3:47
all of the toppings to the Arrange section. 3:51
Let's add a line below the call to clear all tables, and then insert the testPizza 3:54
just like we did above, db.pizzaDau.insert and pass in the testPizza. 3:58
Last but not least, we just need to insert all the toppings. 4:06
Remember, the toppings array is created in our app file and 4:10
is available throughout the whole project. 4:13
So let's type toppings.forEach and then for each topping, 4:16
let's insert it into the database, db.toppingDao.insert, 4:25
and pass in it to be the topping. 4:31
Now when we try to insert our new pizza topping both the pizza and 4:35
the topping we'll be inserting will both exist. 4:40
Let's run our test again and hope for the best. 4:43
Perfect. 4:52
Testing is a great way to make sure something works 4:54
before you start trying to weave it into your code base. 4:57
Not only that, it might save you some time by letting you work with just a test 4:59
instead of the whole app. 5:04
Okay, our tests are written, and 5:06
we're pretty sure our data layer is ready for action. 5:08
Coming up we'll dive back into the UI, and connect it to our database. 5:11