Problem:
When running a test with Gradle and trying to print to System.out or System.err nothing happens. How to make Gradle to display standard output?
Solution:
Here’s sample Gradle buildscript:
buildscript {
repositories {
mavenCentral()
}
}
apply plugin: 'java'
apply plugin: 'groovy'
repositories {
mavenCentral()
}
dependencies {
compile "org.codehaus.groovy:groovy-all:2.4.1"
testCompile "org.spockframework:spock-core:1.0-groovy-2.4"
}
And here’s a sample test class that prints to standard output:
package com.farenda.solved
import spock.lang.Specification
class StandardOutPrintTest extends Specification {
def 'should tell nothing but the true'() {
println('Inside the test!')
expect:
42 == 42
}
}
Now, when you run the test from the console, you will see that it prints nothing:
$> gradle test --tests com.farenda.solved.StandardOutPrintTest :compileJava UP-TO-DATE :compileGroovy UP-TO-DATE :processResources UP-TO-DATE :classes UP-TO-DATE :compileTestJava UP-TO-DATE :compileTestGroovy UP-TO-DATE :processTestResources UP-TO-DATE :testClasses UP-TO-DATE :test UP-TO-DATE BUILD SUCCESSFUL Total time: 7.158 secs
The problem is that Gradle is not logging messages printed to standard out/err, so you have to tell it to do that in your buildscript, using the following command:
buildscript {
repositories {
mavenCentral()
}
}
apply plugin: 'java'
apply plugin: 'groovy'
repositories {
mavenCentral()
}
// this turns logging on in tests:
test.testLogging.showStandardStreams = true
dependencies {
compile "org.codehaus.groovy:groovy-all:2.4.1"
testCompile "org.spockframework:spock-core:1.0-groovy-2.4"
}
Now, when you rerun the test it will print standard out/err as expected:
$> gradle cleanTest test --tests com.farenda.solved.StandardOutPrintTest
:cleanTest
:compileJava UP-TO-DATE
:compileGroovy UP-TO-DATE
:processResources UP-TO-DATE
:classes UP-TO-DATE
:compileTestJava UP-TO-DATE
:compileTestGroovy UP-TO-DATE
:processTestResources UP-TO-DATE
:testClasses UP-TO-DATE
:test
com.farenda.solved.StandardOutPrintTest > should tell nothing but the true STANDARD_OUT
Inside the test!
BUILD SUCCESSFUL
Total time: 8.684 secs
It works as advertised! :-) As you can see, I had to rerun the test with cleanTest task to make Gradle to actually run the test. It is because when Gradle sees that nothing has changed it does nothing.
