Android Gradle DexException: Multiple dex files define Lorg/hamcrest/Description

Question

com.android.dex.DexException: Multiple dex files define Lorg/hamcrest/Description

occurring while trying to do a debug build/test either via Android Studio or via Gradle command-line on my application.

The release build (without tests) works fine but as soon as testing is included (hamcrest being a testing library), the build fails with the above error.

I've checked my module dependencies and there's no duplicate requirements which gradle -q dependencies corroborates.

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Project settings.gradle

include ':[library module]' include ':[main module]' 

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Project build.gradle

buildscript {     repositories {         mavenCentral()     }     dependencies {         classpath 'com.android.tools.build:gradle:0.9.+'         classpath 'org.robolectric.gradle:gradle-android-test-plugin:0.9.+'     } }  allprojects {     repositories {         mavenCentral()     } } 

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[library module] build.gradle

apply plugin: 'android-library'  android {     compileSdkVersion 19     buildToolsVersion "19.0.0"      defaultConfig {         minSdkVersion 14         targetSdkVersion 19     }      packagingOptions {         exclude 'META-INF/LICENSE.txt'         exclude 'META-INF/NOTICE.txt'     } }  dependencies {     compile 'com.google.zxing:core:3.0.+'     compile 'com.bugsnag:bugsnag-android:2.1.1+' } 

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[main module] build.gradle

apply plugin: 'android'  android {     signingConfigs {     release {         [...]     } }      sourceSets {         main {             manifest.srcFile 'src/main/AndroidManifest.xml'             res.srcDirs = ['src/main/res']         }         androidTest {             setRoot('src/test')         }         instrumentTest {         }     }      compileSdkVersion 19     buildToolsVersion '19.0.0'      defaultConfig {         minSdkVersion 14         targetSdkVersion 19         testPackageName "[main.packageName].tests"     }      buildTypes {         release {             runProguard false             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'         }     }      packagingOptions {         exclude 'META-INF/LICENSE.txt'         exclude 'META-INF/NOTICE.txt'     } }  apply plugin: 'android-test'    androidTest {     // configure the set of classes for JUnit tests     include '**/*Test.class'      // configure max heap size of the test JVM     maxHeapSize = "2048m" }  repositories {     maven { url 'https://repo.commonsware.com.s3.amazonaws.com' }     maven { url 'https://oss.sonatype.org/content/repositories/snapshots/' } }  dependencies {     androidTestCompile 'junit:junit:4.10'     androidTestCompile 'org.robolectric:robolectric:2.3-SNAPSHOT'     androidTestCompile 'com.squareup:fest-android:1.0.+'     compile project(':[library module]')     compile 'com.github.gabrielemariotti.changeloglib:library:1.4.+'     compile 'com.google.code.gson:gson:2.2.4'     compile 'com.google.android.gms:play-services:+'     compile 'com.android.support:appcompat-v7:+'     compile ('de.keyboardsurfer.android.widget:crouton:1.8.+') {         exclude group: 'com.google.android', module: 'support-v4'     }     compile files('libs/CWAC-LoaderEx.jar')     compile 'com.squareup.okhttp:okhttp:1.5.+'     compile 'com.octo.android.robospice:robospice:1.4.11'     compile 'com.octo.android.robospice:robospice-cache:1.4.11'     compile 'com.octo.android.robospice:robospice-retrofit:1.4.11'     compile 'com.commonsware.cwac:security:0.1.+'     compile 'com.readystatesoftware.sqliteasset:sqliteassethelper:+' } 

Answer 1

I solved the error by looking in Android Studio for the exact class called 'Description'. It turned out to be present in 3 jars. One from junit, one from a direct dependency and one from mockito.

It turns out that junit, instead of a normal dependency, includes the Hamcrest classes in the junit jar.

To be able to solve the problem include junit-dep instead of junit.

so change

androidTestCompile('junit:junit:4.8.+')

to

androidTestCompile('junit:junit-dep:4.8.+')

Mockito has the same problem/solution: use mockito-core.1.9.5.jar instead of mockito-all.1.9.5.jar