Using multiple TestRules in the same test

Question

I have written a custom TestRule to use with my Android test suite. It populates a table in the database used by the app under test. Now I need to use this DataRule along with ActivityTestRule. Can I have two fields of my test class annotated with @Rule? How do I control the order in which the rules are applied?

Background:

The Android API provides a TestRule for starting an Activity which is the core class for every app with a UI. My app has a database and I have several tests which require the database to be pre-populated with some known data. Previously, with JUnit3-based tests, I used an abstract superclass to centralize the code which prepares the database and then I extended this superclass for different test cases. Now I am trying to implement the same logic using JUnit 4. I learned recently that test rules are one way to provide logic which is reused across tests, so I am trying to move the logic from my superclass to a test rule. Is this an appropriate way to achieve my goal?

Answer 1

You certainly can have multiple @Rule fields in a single test. I'm not sure what the default ordering of rule application is, or if it's even well-defined. However, if ordering is important you can control it with a RuleChain which allows you to define an order on how rules are applied when you have multiple rules in a test case.

From the Javadoc...

@Rule
public RuleChain chain = RuleChain
                           .outerRule(new LoggingRule("outer rule")
                           .around(new LoggingRule("middle rule")
                           .around(new LoggingRule("inner rule");

Answer 2

RuleChain is deprecated and since 4.13 you can make use of order parameter in Rule.

org.junit.Rule annotation has a parameter "order" which you can use to order the Rules in one file.

check the doc in the link below

Rule.java