We have defined the plugin and used the plugin in the same build file. We will see how we can extract the plugin code from the build file and put it in a separate source file in the project source directory. Also, we will learn how we can test the plugin.
When we define the plugin in our build file, we cannot re-use it in other projects. And we now have the definition and usage of the plugin in the same file. To separate the definition and usage, we can create the plugin class in the buildSrc directory of a Gradle project. In a Gradle multi-project, we must use the buildSrc directory of the root project. This means, for a multi-project build, we can re-use the plugin in the other projects of the multi-project build.
We already learned when we wrote a custom task that any sources in the buildSrc directory are automatically compiled and added to the classpath of the project. First, we create the directory buildSrc/src/main/groovy/sample. In this directory, we create a file called InfoPlugin.groovy with the following code:
package sample
import org.gradle.api.*
class InfoPlugin implements Plugin<Project> {
void apply(Project project) {
project.extensions.create('info', InfoPluginExtension)
project.task('info') << {
println "$project.info.prefix: $project.gradle.gradleVersion"
}
}
}Next, we create the file InfoPluginExtension.groovy in the directory:
package sample
class InfoPluginExtension {
String prefix
}In our build file in the root of the project, we reference our plugin with the package and class name:
apply plugin: sample.InfoPlugin
info {
prefix = 'Gradle version'
}When we run the info task, we see in the output that first the plugin code is compiled, and then the info task is executed:
$ gradle :buildSrc:compileJava UP-TO-DATE :buildSrc:compileGroovy :buildSrc:processResources UP-TO-DATE :buildSrc:classes :buildSrc:jar :buildSrc:assemble :buildSrc:compileTestJava UP-TO-DATE :buildSrc:compileTestGroovy UP-TO-DATE :buildSrc:processTestResources UP-TO-DATE :buildSrc:testClasses UP-TO-DATE :buildSrc:test :buildSrc:check :buildSrc:build :info Gradle version: 1.1 BUILD SUCCESSFUL Total time: 2.743 secs
One of the tasks that are executed for the project in the buildSrc directory is the test task. We can write test cases for testing the plugin code, just like in any other project. We add a build.gradle file in buildSrc and define the dependencies for the JUnit test framework. In the following sample build file, we add a dependency for JUnit:
repositories.mavenCentral()
dependencies {
testCompile 'junit:junit:4.10'
}Next, we can add a test case named InfoPluginTest.groovy in the buildSrc/src/test/groovy/sample directory:
package sample
import org.gradle.api.*
import org.gradle.testfixtures.ProjectBuilder
import org.junit.*
class InfoPluginTest {
@Test
void infoTaskIsAddedToProject() {
final Project project = ProjectBuilder.builder().build()
project.apply plugin: sample.InfoPlugin
assert project.tasks.findByName('info')
}
@Test
void configurePrefix() {
final Project project = ProjectBuilder.builder().build()
project.apply plugin: sample.InfoPlugin
project.info.prefix = 'Sample'
assert project.info.prefix == 'Sample'
}
}We use the ProjectBuilder class to create a fixture for the Project object. We can apply the plugin to the project and then test to see if the info task is available. The Project object cannot execute tasks in the project; it is only for simple checks like this one.
When we invoke the info task from the command line, our test class is compiled and executed. If a test fails, the project will abort, but if all tests pass, the project continues.