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java.lang.NoClassDefFoundError: Test Module could not resolve classes of other Feature Module, Unit Testing - Kotlin - Android

I have the following Project Structure:
Main App
--app
--featureModule1
--featureModule2
--TestKit(Library module)
where Testkit has all dependencies including app and featureModules. The Testkit included all the unit tests related to the features in app and featuremodules.
When i run unit tests from Android studio(Right click-> Run Test in Testkit), they run fine. However whenever i try running it from gradle command: ./gradlew TestKit:testInternalDebugUnitTest, it throws NoClassDefFoundError for all the dependencies of other modules(for both app and feature modules).
Also i have already added implementation and testImplementation dependencies of all the modules in test module.
Please suggest:
Do i need to add path of classes generated in other modules, if yes pls guide where.
Also running Test with Coverage fails with
java.lang.VerifyError: Bad return type
Please suggest what am i doing wrong here.
Note:
I have created a Testkit because of the multiple open issues of Roboelectric in feature modules for ex: https://github.com/robolectric/robolectric/issues/5428
Versions
AS: 4.0.1
gradle: 4.0.1
gradle-wrapper: 6.5
Robolectric: 4.3.1

I was able to solve the problem using the following runtime test dependencies:
testRuntimeOnly(files("${projectDir}/../app/build/intermediates/app_classes/internalDebug/classes.jar"))
testRuntimeOnly(files("${projectDir}/../featureModule1/build/intermediates/app_classes/internalDebug/classes.jar"))
testRuntimeOnly(files("${projectDir}/../featureModule2/build/intermediates/app_classes/internalDebug/classes.jar"))
inside build.gradle of Testkit.
Can refer to the following link for more details:https://github.com/android/app-bundle-samples/issues/11#issuecomment-675725610

JUnit5 not generating test-result TEST-*.xml that JUnit4 used to

When I used JUnit4 in my projects it seemed that each time a test ran, it would generate a TEST-*.xml report in app/build/test-result. Jenkins would use these XML reports to display failing and passing tests on each build.
I've replaced JUnit4 with JUnit5 with the following in build.gradle:
testImplementation "org.junit.jupiter:junit-jupiter-api:5.3.2"
When running tests with JUnit 5, I'm no longer seeing these TEST-*.xml files being generated. As soon as I drop back to JUnit4, they are.
Is this no longer available in JUnit5 or is there something I have to set on each test in order to get these XML reports?

Found the solution. In order for the XML reports to be generated for each test you need to include the following in your build.gradle:
testImplementation 'org.junit.jupiter:junit-jupiter-api:5.3.2'
testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.3.2'
As well as:
tasks.withType(Test) {
useJUnitPlatform()
}
This other post may also be of use to others: JUnit5 integration tests with Gradle 4.6

Kotlin & Mockito unit tests failing in gradle

Running unit tests locally on Android Studio works fine but when I run it with gradle using ./gradlew test. The tests fails with the exception saying Mockito cannot spy/mock final classes. I thought using mockito with the inline extension was supposed to fix this. I have this dependency
in my gradle file testImplementation "org.mockito:mockito-inline:2.18.0"
Is there something that I'm missing?

What helped me, is to create a MockMaker file and to put it into test resources.
File
org.mockito.plugins.MockMaker (literally) that contains only this line
mock-maker-inline
and place it into
test/resources/mockito-extensions.
Answer - https://stackoverflow.com/a/50449830/3569545

Android unit test support does not work in android library modules

I am writing junit tests on android project using the new unit test support http://tools.android.com/tech-docs/unit-testing-support.
While the unit tests run on the 'com.android.application' module perfectly but they always fail on the 'com.android.library' modules. This has not been documented in http://tools.android.com/tech-docs/unit-testing-support . So I wonder whether I am the culprit.
When I write those tests on library modules, the tests can not find the classes on the module and always gives following errors:
package does not exist
error: cannot find symbol
The android unit test support is in experimental phase right now, but is there a solution to it.
UPDATE
I have added this issue to android issue tracker https://code.google.com/p/android/issues/detail?id=161038

It looks like the task to compile the unit tests doesn't depend on the task to compile the library code.
The following fixed it for me:
afterEvaluate {
tasks['assembleDebugUnitTest'].dependsOn(tasks['assembleDebug'])
}
I run the tests using
./gradlew testDebug
If you don't want to modify your build.gradle, manually specify the assembleDebug task on the command line should also do the trick:
./gradlew assembleDebug testDebug

In my android library project I also failed to get the tests running. What I did was create a test application that uses the library and wrote tests in the application that call the library methods.
This might not be the ideal solution, but was the way we got this to work.

Have a look over here https://github.com/nenick/AndroidStudioAndRobolectric
There you can run unit tests on libraries and flavors. And no you don't need to use Robolectric as Gaurav Vashisth stated. You can if you want to.
Here is an example of JUnit test in a library module

Android Studio 1.1, simple junit test setup

I have read around, there are a number of extensive answers (like this one) but the Android world evolves so fast that they seem to be a bit outdated and the official documentation still refers to Eclipse with ADT.
I am running AS 1.1 and I am trying to setup simple junit tests to run on the emulator, without Robolectric. If I don't include junit in my build.gradle, it can't find #After, #Before and #Test and I get package org.junit does not exist. Upon adding
// unit tests
androidTestCompile 'junit:junit:4.11'
the error becomes
Error:duplicate files during packaging of APK
[...]/app/build/outputs/apk/app-debug-test-unaligned.apk
Path in archive: LICENSE.txt
Origin 1: [...]/.gradle/caches/modules-2/files-2.1/org.hamcrest/hamcrest-core/1.3/42a25dc3219429f0e5d060061f71acb49bf010a0/hamcrest-core-1.3.jar
Origin 2: [...]/.gradle/caches/modules-2/files-2.1/junit/junit/4.11/4e031bb61df09069aeb2bffb4019e7a5034a4ee0/junit-4.11.jar
You can ignore those files in your build.gradle:
android {
packagingOptions {
exclude 'LICENSE.txt'
}
}
Following the console suggestion of excluding LICENSE.txt, it then works but it feels like a hack. So I'm wondering, am I maybe missing something? Thanks.

Android Studio unit testing support comes in 1.1 Beta 4 (release announcement) with Gradle plugin version 1.1.0-rc1.
More info in official document.
However it is experimental feature for now. E.g. it breaks installDebug gradle task.
For using JUnit in instrumentation tests there is good guide for Espresso library and another covering new AndroidJUnitRunner.

If it's any use I set up a boiler plate project allowing the use of Unit tests and Espresso tests by the use of switching build variants. You won't need the use of any third party plugins with this.
https://github.com/hitherejoe/Android-Boilerplate