Could not launch intent Android Junit Test Cases

I was trying to run some junit test cases for my Android application. Here is my code:

@Rule
public ActivityTestRule<MainActivity_> rule = new ActivityTestRule<>(MainActivity_.class);

@Test
public void testRead() {
    MainActivity mainActivity = rule.getActivity();
    tpViewModel vm = new tpViewModel(mainActivity.getApplication());

    assertNotNull("Failed.", vm.getWords());
}

The error message I am getting from running the above test method:

java.lang.RuntimeException: Could not launch intent Intent { act=android.intent.action.MAIN flg=0x14000000 cmp=com.mainapp/.MainActivity_ } within 45 seconds. Perhaps the main thread has not gone idle within a reasonable amount of time? There could be an animation or something constantly repainting the screen. Or the activity is doing network calls on creation? See the threaddump logs. For your reference the last time the event queue was idle before your activity launch request was 1529479548185 and now the last time the queue went idle was: 1529479548185. If these numbers are the same your activity might be hogging the event queue.
at android.support.test.runner.MonitoringInstrumentation.startActivitySync(MonitoringInstrumentation.java:419)
at android.support.test.rule.ActivityTestRule.launchActivity(ActivityTestRule.java:219)
at android.support.test.rule.ActivityTestRule$ActivityStatement.evaluate(ActivityTestRule.java:268)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runners.Suite.runChild(Suite.java:128)
at org.junit.runners.Suite.runChild(Suite.java:27)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
at android.support.test.internal.runner.TestExecutor.execute(TestExecutor.java:58)
at android.support.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:375)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:2074)

Any ideas? Thanks!