Gradle connectedCheck fails with 'No tests found' after migrating to AndroidX

Question

I'm working on a multi-module project, and after making the transition from the support libraries to AndroidX, ./gradlew connectedCheck fails:

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':MyProject:connectedDebugAndroidTest'.
> There were failing tests. See the report at: file:///Users/justinpollard/Dev/android-app/MyProject/build/reports/androidTests/connected/index.html

A bit further up, I see this message:

11:48:13 I/RemoteAndroidTest: Running am instrument -w -r   com.myproject.test/androidx.test.runner.AndroidJUnitRunner on Pixel XL - 9
11:48:13 V/ddms: execute: running am instrument -w -r   com.myproject.test/androidx.test.runner.AndroidJUnitRunner
11:48:15 V/InstrumentationResultParser: INSTRUMENTATION_RESULT: shortMsg=Process crashed.
11:48:15 I/InstrumentationResultParser: test run failed: 'Instrumentation run failed due to 'Process crashed.''
Starting 0 tests on Pixel XL - 9
Tests on Pixel XL - 9 failed: Instrumentation run failed due to 'Process crashed.'
11:48:15 I/XmlResultReporter: XML test result file generated at /Users/justinpollard/Dev/android-app/MyProject/build/outputs/androidTest-results/connected/TEST-Pixel XL - 9-MyProject-.xml. Total tests 0,
11:48:15 V/InstrumentationResultParser: INSTRUMENTATION_CODE: 0
11:48:15 V/InstrumentationResultParser:
11:48:15 V/ddms: execute 'am instrument -w -r   com.myproject.test/androidx.test.runner.AndroidJUnitRunner' on 'HT73Y0200438' : EOF hit. Read: -1
11:48:15 V/ddms: execute: returning

com.android.builder.testing.ConnectedDevice > No tests found.[Pixel XL - 9] FAILED
No tests found. This usually means that your test classes are not in the form that your test runner expects (e.g. don't inherit from TestCase or lack @Test annotations).

This makes it seem like the failure is caused by a test apk crash before the tests can run. When I run one of my connected tests from Android Studio, I see a little more information:

2019-05-13 11:55:55.927 29839-29839/? E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.myproject, PID: 29839
    java.lang.RuntimeException: Unable to instantiate instrumentation ComponentInfo{com.myproject.test/androidx.test.runner.AndroidJUnitRunner}: java.lang.ClassNotFoundException: Didn't find class "androidx.test.runner.AndroidJUnitRunner" on path: DexPathList[[zip file "/system/framework/android.test.runner.jar", zip file "/system/framework/android.test.mock.jar", zip file "/data/app/com.myproject.test-2MzWVeeaNLfexBOU_5tLPw==/base.apk", zip file "/data/app/com.myproject-Hd0c3YX8pUlOxZVK3mlgMA==/base.apk"],nativeLibraryDirectories=[/system/lib64, /vendor/lib64]]
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5855)
        at android.app.ActivityThread.access$1100(ActivityThread.java:200)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1656)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6718)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: java.lang.ClassNotFoundException: Didn't find class "androidx.test.runner.AndroidJUnitRunner" on path: DexPathList[[zip file "/system/framework/android.test.runner.jar", zip file "/system/framework/android.test.mock.jar", zip file "/data/app/com.myproject.test-2MzWVeeaNLfexBOU_5tLPw==/base.apk", zip file "/data/app/com.myproject-Hd0c3YX8pUlOxZVK3mlgMA==/base.apk"],nativeLibraryDirectories=[/system/lib64, /vendor/lib64]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:134)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5851)
        at android.app.ActivityThread.access$1100(ActivityThread.java:200) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1656) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:193) 
        at android.app.ActivityThread.main(ActivityThread.java:6718) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 
        Suppressed: java.lang.NoClassDefFoundError: Failed resolution of: Landroidx/test/runner/MonitoringInstrumentation;
        at java.lang.VMClassLoader.findLoadedClass(Native Method)
        at java.lang.ClassLoader.findLoadedClass(ClassLoader.java:738)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:363)
                ... 10 more
     Caused by: java.lang.ClassNotFoundException: Didn't find class "androidx.test.runner.MonitoringInstrumentation" on path: DexPathList[[zip file "/system/framework/android.test.runner.jar", zip file "/system/framework/android.test.mock.jar", zip file "/data/app/com.myproject.test-2MzWVeeaNLfexBOU_5tLPw==/base.apk", zip file "/data/app/com.myproject-Hd0c3YX8pUlOxZVK3mlgMA==/base.apk"],nativeLibraryDirectories=[/system/lib64, /vendor/lib64]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:134)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
                ... 13 more

It's surprising to me that AndroidJUnitRunner and MonitoringInstrumentation are not found on the path since I include androidx.text:runner in the app-level build.gradle dependencies:

dependencies {
    ...
    androidTestImplementation(
        "androidx.test.ext:junit:1.1.0",
        "androidx.test:rules:1.1.0",
        "androidx.test:runner:1.1.0",
        "androidx.test.espresso:espresso-core:3.1.0",
    )
    ...
}

I've also made sure I'm following the instructions listed here at https://developer.android.com/training/testing/set-up-project:

1) My project build.gradle includes the google() repository (the instructions do say to include this in the app-level build.gradle, but I'm assuming that's incorrect given allprojects exists in the project-level build.gradle?)

2) I've got my dependencies listed in the app-level dependencies.androidTestImplementation (see above)

3) Add useLibrary 'android.test.runner' to the android section of my app build.gradle

4) Add <uses-library android:name="android.test.runner" android:required="false" /> to the app's AndroidManifest.xml (the instructions make it seem like this may not be required since I'm using gradle to run the tests)

For reference, without including an entire test, here's an illustrative example of my setup:

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;

import androidx.test.ext.junit.runners.AndroidJUnit4;

@RunWith(AndroidJUnit4.class)
public class ExampleTest {

    @Before
    public void setUp() throws Exception {
        // Setup here
    }

    @After
    public void tearDown() {
        // Tear down here
    }

    @Test
    public void testExample() {
        // Test code here
    }

    ...
}

Can anyone help me get these tests up and running again? Thanks!