start with a test and maybe it will actually get used, Eventually.

build.gradle

@@ -42,7 +42,7 @@ android {
         targetSdkVersion 28
         versionCode = 1_01_02
         versionName = "1.1.2"
-        testInstrumentationRunner = "android.support.test.runner.AndroidJUnitRunner"
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }
 
     buildTypes {

src/androidTest/java/cash/z/wallet/sdk/ExampleInstrumentedTest.java

@@ -1,26 +0,0 @@
-package cash.z.wallet.sdk;
-
-import android.content.Context;
-import android.support.test.InstrumentationRegistry;
-import android.support.test.runner.AndroidJUnit4;
-
-import org.junit.Test;
-import org.junit.runner.RunWith;
-
-import static org.junit.Assert.*;
-
-/**
- * Instrumented test, which will execute on an Android device.
- *
- * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
- */
-@RunWith(AndroidJUnit4.class)
-public class ExampleInstrumentedTest {
-	@Test
-	public void useAppContext() {
-		// Context of the app under test.
-		Context appContext = InstrumentationRegistry.getTargetContext();
-
-		assertEquals("cash.z.wallet.sdk.test", appContext.getPackageName());
-	}
-}

src/androidTest/java/cash/z/wallet/sdk/dao/ComplactBlockDaoTest.kt

@@ -0,0 +1,17 @@
+package cash.z.wallet.sdk.dao
+
+import androidx.test.runner.AndroidJUnit4
+import org.junit.Assert.*
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class ComplactBlockDaoTest {
+
+    private var dao: CompactBlockDao? = null
+
+    @Test
+    fun testDaoExists() {
+        assertNotNull(dao)
+    }
+}

src/main/java/cash/z/wallet/sdk/dao/CompactBlockDao.kt

@@ -0,0 +1,4 @@
+package cash.z.wallet.sdk.dao
+
+interface CompactBlockDao {
+}