Gradle - uploadArchives generated snapshot is different from createJar - gradle

Question

With my build.gradle file I am creating a jar file using a createJar task, which I later upload using an upload using an uploadArchives task.
The project is in groovy, structured like:
/src/main/groovy/package.name
/src/test/groovy
It's a test jar file, where the main class is in /src/test/groovy and it uses for processing classes from /src/main/groovy/package.name
The createJar task works and creates the jar that I need correctly.
So far so good.
The problem is when I run uploadArchives, which generates a snapshot.jar and it only contains the classes from /src/main/groovy/package.name
Why are the 2 jar files different ?
How can I make uploadArchives to upload the jar from createJar (or at least include the test classes as well & run it using the main class specified in createJar) ?
In build.gradle I have something like :
apply plugin: 'groovy'
apply plugin: 'java'
apply plugin: 'maven'
sourceCompatibility = 1.5
repositories {
mavenCentral()
}
artifacts {
archives file: file('./build/libs/name-'+version+'.jar'), name: 'name', type: 'jar'
}
task createJar(type: Jar) {
classifier 'test'
from sourceSets.test.output
manifest {
attributes 'Implementation-Title': 'Gradle Jar File',
'Implementation-Version': version,
'Main-Class': 'MainClassName'
}
}
uploadArchives {
repositories {
mavenDeployer {
repository(url: "http://url/snapshotsFolder/") {
authentication(userName: "user", password: "pass")
}
}
}
}

Answer 1

To extend my comment, let me add an example:
jar {
classifier 'test'
from sourceSets.test.output
manifest {
attributes 'Implementation-Title': 'Gradle Jar File', 'Implementation-Version': version, 'Main-Class': 'MainClassName'
}
}
This will configure the task jar of type Jar, which is created by the java plugin.