Specifying Gradle dependencies for *.jar files - junit

Question

This must be straight forward but I fail to see where group: name: and version: come from for a particular jar file. For example from Gradle's documentation.
dependencies {
compile group: 'org.hibernate', name: 'hibernate-core', version: '3.6.7.Final'
testCompile group: 'junit', name: 'junit', version: '4.+'
testRuntime "org.hamcrest:SelfDescribing:1.+"
}
I'm trying to make use of a hamcrest jar for my junit testing. I need hamcrest for runtime testing but I don't know how to correctly specify this. Below is my build.gradle file. This test project will build successfully but will not run the unit tests due to unresolved dependencies.
apply plugin: 'java'
apply plugin: 'eclipse-wtp'
version = '1.0'
compileJava.destinationDir = file("$buildDir/classes/test")
sourceSets {
main {
java {
srcDir 'src'
}
}
}
repositories {
flatDir dirs: "C:/eclipse/plugins/org.junit_4.11.0.v201303080030"
flatDir dirs: "C:/eclipse/plugins"
}
dependencies {
compile "junit:junit:4"
testCompile "junit:junit:4"
testRuntime "org.hamcrest:SelfDescribing:1.+"
}
test {
testLogging.showStandardStreams = true
testLogging {
events 'started', 'passed', 'skipped', 'failed', 'standardOut', 'standardError'
exceptionFormat 'short'
}
}
jar {
manifest.attributes provider: 'gradle'
}

Answer 1

To add a dependency on a jar file, add a statement like this to your dependencies block:
compile files('path/to/archive.jar')
A popular approach is this, which will automatically pick up all jar files in a libs directory:
compile fileTree(dir: 'path/to/libs', include: '*.jar')

Answer 2

When using a flatDir repository, you'll have to make sure that:
Artifact files are contained directly in the specified directory (not in a subdirectory).
Artifact filenames match the pattern module-version.extension (e.g. junit-4.jar) or module.extension (e.g. junit.jar).
Alternatively, you could use file dependencies as described in Scott's answer.
PS: I'm not sure if version ranges work with flatDir repositories.