How to run unit tests with dependency to an Android library module? - unit-testing

Question

Whenever I try to run unit-tests for classes in my app module that depend on classes from an library module, I get this:
java.lang.NoClassDefFoundError: de/ivu/junittest/DummyData
at de.ivu.junittest.app.DummyModel.<init>(DummyModel.java:16)
at DummyModelTest.testInstantiation(DummyModelTest.java:7)
...
In the above sample, DummyData is part of the lib module, while DummyModel is part of the app module. DummyModel has a member of type DummyData, but instantiating this in the test-class DummyModelTest causes the aforementioned exception at test-time.
The project structure is as follows:
JUnitTestProject
app [module]
src
main
java
de.ivu.junittest.app
DummyModel.java
...
...
test
java
de.ivu.junittest.app
DummyModelTest.java
...
lib [module]
src
main
java
de.ivu.junittest
DummyData.java
...
...
The build.gradle for the app module contains the following:
apply plugin: 'android'
android {
compileSdkVersion 19
buildToolsVersion "19.0.1"
defaultConfig {
minSdkVersion 7
targetSdkVersion 19
versionCode 1
versionName "1.0"
}
buildTypes {
release {
runProguard false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
}
}
}
sourceSets {
unitTest {
java.srcDir file('src/test/java')
resources.srcDir file('src/test/res')
}
}
configurations {
unitTestCompile.extendsFrom runtime
unitTestRuntime.extendsFrom unitTestCompile
}
dependencies {
compile 'com.android.support:appcompat-v7:+'
compile project (':lib')
compile fileTree(dir: 'libs', include: ['*.jar', '*.aar'])
unitTestCompile files("$project.buildDir/classes/release")
unitTestCompile 'junit:junit:4.+'
unitTestCompile 'org.robolectric:robolectric:2.+'
unitTestCompile 'com.google.android:android:4.+'
unitTestCompile project (':lib')
unitTestCompile fileTree(dir: 'libs', include: ['*.jar', '*.aar'])
instrumentTestCompile 'junit:junit:4.+'
instrumentTestCompile 'org.robolectric:robolectric:2.+'
}
task unitTest(type:Test, dependsOn: assemble) {
testClassesDir = project.sourceSets.unitTest.output.classesDir
classpath = project.sourceSets.unitTest.runtimeClasspath
}
check.dependsOn unitTest
And finally the source of the three java-classes, starting with DummyData:
package de.ivu.junittest;
import android.util.Log;
public class DummyData {
private int data;
public int getData() {
return data;
}
public void setData(int data) {
this.data = data;
}
}
The DummyModel class:
package de.ivu.junittest.app;
import android.util.Log;
import de.ivu.junittest.DummyData;
public class DummyModel {
private DummyData data = new DummyData();
public void setData(int data) {
this.data.setData(data);
}
public int getData() {
return this.data.getData();
}
}
And finally, DummyModelTest:
import static org.junit.Assert.assertEquals;
import org.junit.runner.RunWith;
import org.junit.Test;
import org.robolectric.RobolectricTestRunner;
import de.ivu.junittest.app.DummyModel;
#RunWith(RobolectricTestRunner.class)
public class DummyModelTest {
#Test
public void testInstantiation() {
DummyModel model = new DummyModel();
model.setData(42);
assertEquals(model.getData(), 42);
}
}
After trying more than a dozen different things, any help is deeply appreciated.

Answer 1

The trick is to add the other modules' classes directories as dependency. So you end up with unitTestCompile files instead of unitTestCompile project:
dependencies {
...
unitTestCompile files("../lib/classes/release")
...
}
Not very beautiful, nor very intuitive, but it works with my current setup (Gradle 1.10, Build Tools 19.0.1, and Android-Gradle-plugin 0.8).