Spock basics
Spock (homepage) is like its authors say 'testing and specification framework'. Spock combines very elegant and natural syntax with the powerful capabilities. And what is most important it is easy to use.
One note at the very beginning: I assume that you are already familiar with principles of Test Driven Development and you know how to use testing framework like for example JUnit.
So how can I start?
Writing spock specifications is very easy. We need basic configuration of Spock and Groovy dependencies (if you are using mavenized project with Eclipse look to my previous post: Spock, Java and Maven). Once we have everything set up and running smooth we can write our first specs (spec or specification is equivalent for test class in other frameworks like JUnit of TestNG).
What is great with Spock is fact that we can use it to test both Groovy projects and pure Java projects or even mixed projects.
What is great with Spock is fact that we can use it to test both Groovy projects and pure Java projects or even mixed projects.
Let's go!
Every spec class must inherit from spock.lang.Specification class. Only then test runner will recognize it as test class and start tests. We will write few specs for this simple class: User class and few tests not connected with this particular class.
We start with defining our class:
import spock.lang.*
class UserSpec extends Specification {
}
All activites we want to perform before each test method, are to be put in def setup() {...} method and everything we want to be run after each test should be put in def cleanup() {...} method (they are equivalents for JUnit methods with @Before and @After annotations).
It can look like this:
class UserSpec extends Specification {
User user
Document document
def setup() {
user = new User()
document = DocumentTestFactory.createDocumentWithTitle("doc1")
}
def cleanup() {
}
}
class UserSpec extends Specification {
User user = new User()
Document document = DocumentTestFactory.createDocumentWithTitle("doc1")
def setup() {
}
def cleanup() {
}
}
What is more readable or preferred? It is just a matter of taste because according to Spock docs behaviour is the same in these two cases.
It is worth mentioning that JUnit @BeforeClass/@AfterClass are also present in Spock as def setupSpec() {...} and def cleanupSpec() {...}. They will be runned before first test and after last test method.
First tests
In Spock every method in specification class, expect setup/cleanup, is treated by runner as a test method (unless you annotate it with @Ignore).
Very interesting feature of Spock and Groovy is ability to name methods with full sentences just like regular strings:
class UserSpec extends Specification {
// ...
def "should assign coment to user"() {
// ...
}
}
Test method (also called feature method) is logically divided into few blocks, each with its own purpose. Blocks are defined like labels in Java (but they are transformed with Groovy AST transform features) and some of them must be put in code in specific order.
Most basic and common schema for Spock test is:
class UserSpec extends Specification {
// ...
def "should assign coment to user"() {
given:
// do initialization of test objects
when:
// perform actions to be tested
then:
// collect and analyze results
}
}
But there are more blocks like:
- setup
- expect
- where
- cleanup
given block
This block is used to setup test objects and their state. It has to be first block in test and cannot be repeated. Below is little example how can it be used:
In this code given block contains initialization of test objects and nothing more. We create simple user without any specified attributes and project with given name. In case when some of these objects could be reused in more feature methods, it could be worth putting initialization in setup method.
class UserSpec extends Specification {
// ...
def "should add project to user and mark user as project's owner"() {
given:
User user = new User()
Project project = ProjectTestFactory.createProjectWithName("simple project")
// ...
}
}
In this code given block contains initialization of test objects and nothing more. We create simple user without any specified attributes and project with given name. In case when some of these objects could be reused in more feature methods, it could be worth putting initialization in setup method.
when and then blocks
When block contains action we want to test (Spock documentation calls it 'stimulus'). This block always occurs in pair with then block, where we are verifying response for satisfying certain conditions. Assume we have this simple test case:
In when block there is a call of tested method and nothing more. After we are sure our action was performed, we can check for desired conditions in then block.
Then block is very well structured and its every line is treated by Spock as boolean statement. That means, Spock expects that we write instructions containing comparisons and expressions returning true or false, so we can create then block with such statements:
Sometimes we expect that our method throws an exception under given circumstances. We can write test for it with use of thrown method:
In this test we want to make sure that passing incorrect parameters is correctly handled by tested method and that method throws an exception in response. In case you want to be certain that method does not throw particular exception, simply use notThrown method.
That were very simple tests with standard Spock test layout and canonical divide into given/when/then parts. But Spock offers more possibilities in writing tests and provides more blocks.
In this example, Spock creates variable called email which is used when calling method being tested. Internally feature method is called once, but framework iterates over given values and calls expect/when block as many times as there are values (however, if we use @Unroll annotation Spock can create separate run for each of given values, more about it in one of next examples).
Now, lets assume that we want our feature method to test both successful and failure validations. To achieve that goal we can create few parameterized variables for both input parameter and expected result. Here is a little example:
Another useful feature of Spock during parameterizing test is its ability to "unroll" each parameterized test. Feature method from previous example could be defined as (the body stays the same, so I do not repeat it):
class UserSpec extends Specification {
// ...
def "should assign user to comment when adding comment to user"() {
given:
User user = new User()
Comment comment = new Comment()
when:
user.addComment(comment)
then:
comment.getUserWhoCreatedComment().equals(user)
}
// ...
}
In when block there is a call of tested method and nothing more. After we are sure our action was performed, we can check for desired conditions in then block.
Then block is very well structured and its every line is treated by Spock as boolean statement. That means, Spock expects that we write instructions containing comparisons and expressions returning true or false, so we can create then block with such statements:
user.getName() == "John"
user.getAge() == 40
!user.isEnabled()
Sometimes we expect that our method throws an exception under given circumstances. We can write test for it with use of thrown method:
class CommentSpec extends Specification {
def "should throw exception when adding null document to comment"() {
given:
Comment comment = new Comment()
when:
comment.setCommentedDocument(null)
then:
thrown(RuntimeException)
}
}
In this test we want to make sure that passing incorrect parameters is correctly handled by tested method and that method throws an exception in response. In case you want to be certain that method does not throw particular exception, simply use notThrown method.
expect block
Expect block is primarily used when we do not want to separate when and then blocks because it is unnatural. It is especially useful for simple test (and according to TDD rules all test should be simple and short) with only one condition to check, like in this example (it is simple but should show the idea):
def "should create user with given name"() {
given:
User user = UserTestFactory.createUser("john doe")
expect:
user.getName() == "john doe"
}
More blocks!
That were very simple tests with standard Spock test layout and canonical divide into given/when/then parts. But Spock offers more possibilities in writing tests and provides more blocks.
setup/cleanup blocks
These two blocks have the very same functionality as the def setup and def cleanup methods in specification. They allow to perform some actions before test and after test. But unlike these methods (which are shared between all tests) blocks work only in methods they are defined in.
where - easy way to create readable parameterized tests
Very often when we create unit tests there is a need to "feed" them with sample data to test various cases and border values. With Spock this task is very easy and straighforward. To provide test data to feature method, we need to use where block. Let's take a look at little the piece of code:
def "should successfully validate emails with valid syntax"() {
expect:
emailValidator.validate(email) == true
where:
email }
In this example, Spock creates variable called email which is used when calling method being tested. Internally feature method is called once, but framework iterates over given values and calls expect/when block as many times as there are values (however, if we use @Unroll annotation Spock can create separate run for each of given values, more about it in one of next examples).
Now, lets assume that we want our feature method to test both successful and failure validations. To achieve that goal we can create few parameterized variables for both input parameter and expected result. Here is a little example:
def "should perform validation of email addresses"() {
expect:
emailValidator.validate(email) == result
where:
email result }
def "should perform validation of email addresses"() {
expect:
emailValidator.validate(email) == result
where:
email | result
"WTF" | false
"@domain" | false
"foo@bar.com" | true
"a@test" | false
}
Another useful feature of Spock during parameterizing test is its ability to "unroll" each parameterized test. Feature method from previous example could be defined as (the body stays the same, so I do not repeat it):
@Unroll("should validate email #email")
def "should perform validation of email addresses"() {
// ...
}
What next?
Well, that was just quick and short journey through Spock and its capabilities. However, with that basic tutorial you are ready to write many unit tests. In one of my future posts I am going to describe more features of Spock focusing especially on its mocking abilities.