How to copy files to Android emulator to be used in instrumentation tests?

I am trying to run an instrumented unit tests for Android Pie. The test I am building will test the access to expansion files delivered via Play Store APK Expansion files. In manual test this works, but that's, well, manual.

To run the test I push the file over to the emulator:

adb push obb/main.45.org.example.someapp.obb /storage/emulated/0/Android/obb/org.example.someapp/main.45.org.example.someapp.obb

and run tests with gradle connectedFreeDebugAndroidTest. Gradle compiles everything nicely and copies the APK over to the emulator. However, during this process, it seems the expansion file is also cleaned off the device:

> Task :app:connectedFreeDebugAndroidTest
01:18:05 V/ddms: execute: running am get-config
01:18:05 V/ddms: execute 'am get-config' on 'emulator-5554' : EOF hit. Read: -1
01:18:05 V/ddms: execute: returning
01:18:05 D/app-free-debug.apk: Uploading app-free-debug.apk onto device 'emulator-5554'
01:18:05 D/Device: Uploading file onto device 'emulator-5554'
01:18:05 D/ddms: Reading file permision of /tmp/gradle/someapp-android/app/outputs/apk/free/debug/app-free-debug.apk as: rw-r--r--
01:18:05 V/ddms: execute: running pm install -r -t "/data/local/tmp/app-free-debug.apk"
01:18:05 V/ddms: execute 'pm install -r -t "/data/local/tmp/app-free-debug.apk"' on 'emulator-5554' : EOF hit. Read: -1
01:18:05 V/ddms: execute: returning
01:18:05 V/ddms: execute: running rm "/data/local/tmp/app-free-debug.apk"
01:18:05 V/ddms: execute 'rm "/data/local/tmp/app-free-debug.apk"' on 'emulator-5554' : EOF hit. Read: -1
01:18:05 V/ddms: execute: returning
01:18:05 D/app-free-debug-androidTest.apk: Uploading app-free-debug-androidTest.apk onto device 'emulator-5554'
01:18:05 D/Device: Uploading file onto device 'emulator-5554'
01:18:05 D/ddms: Reading file permision of /tmp/gradle/someapp-android/app/outputs/apk/androidTest/free/debug/app-free-debug-androidTest.apk as: rw-r--r--
01:18:05 V/ddms: execute: running pm install -r -t "/data/local/tmp/app-free-debug-androidTest.apk"
01:18:06 V/ddms: execute 'pm install -r -t "/data/local/tmp/app-free-debug-androidTest.apk"' on 'emulator-5554' : EOF hit. Read: -1
01:18:06 V/ddms: execute: returning
01:18:06 V/ddms: execute: running rm "/data/local/tmp/app-free-debug-androidTest.apk"
01:18:06 V/ddms: execute 'rm "/data/local/tmp/app-free-debug-androidTest.apk"' on 'emulator-5554' : EOF hit. Read: -1
01:18:06 V/ddms: execute: returning
01:18:06 I/RemoteAndroidTest: Running am instrument -w -r   -e coverageFile /data/data/org.example.someapp/coverage.ec -e coverage true org.example.someapp.test/android.support.test.runner.AndroidJUnitRunner on Pixel_2_API_28_Android_Pie_(AVD) - 9
01:18:06 V/ddms: execute: running am instrument -w -r   -e coverageFile /data/data/org.example.someapp/coverage.ec -e coverage true org.example.someapp.test/android.support.test.runner.AndroidJUnitRunner
...
01:18:07 V/InstrumentationResultParser: Caused by: java.io.FileNotFoundException: /storage/emulated/0/Android/obb/org.example.someapp/main.45.org.example.someapp.obb: open failed: ENOENT (No such file or directory)

How can I make sure this file exists when tests run?