For security reasons they both require to be signed by the same keystore.
If you use different key for the application and the test you will get error:
Test run failed: Permission Denial: starting instrumentation ComponentInfo{net.retsat1.starlab.test/android.test.InstrumentationTestRunner} from pid=305, uid=305 not allowed because package net.retsat1.starlab.test does not have a signature matching the target net.retsat1.starlabjava.lang.SecurityException: Permission Denial: starting instrumentation ComponentInfo{net.retsat1.starlab.test/android.test.InstrumentationTestRunner} from pid=305, uid=305 not allowed because package net.retsat1.starlab.test does not have a signature matching the target net.retsat1.starlab
During development cycle keys generated by eclipse are usually used. When you are starting to think about release you are preparing the build signed with release key.
In eclipse there is no automatic way to sign for release, so you probably hand over this to ant script or do the signing by hand.
Afterwards if you are lucky your test that had previously run successfully on debug mode will be still passing in release mode. If for some reason this is not true you want to debug your test with eclipse.
When you want to run test(s) against your new build you find that signatures of the test and release apk mismatch.
In eclipse you can set a custom keystore from menu
Windows -> Preferences -> Android - > Build
This unfortunately leads to a problem as you eclipse does not accept release keystore with an error: Keystore was tampered with, or password was incorrect.
To convert release key to debug one that will be acceptable for eclipse, you need to import keystore into new debug keystore with keytool from jdk. This is done with the following command.
keytool -importkeystore -v -srckeystore release.keystore -destkeystore custom-debug.keystore -srcstorepass release-pass -deststorepass android -srcalias release-key -destalias androiddebugkey -srckeypass release-pass -destkeypass android
Of course substitute passwords and alias of source keystore with the one used in creation of release keystore.