added JNI test

I am a little excited about this because it will be a great way to test
Rust functionality quickly and iterate quickly because we will not have
to update and run the full app.

src/androidTest/java/cash/z/wallet/sdk/jni/JniConverterTest.kt

@@ -0,0 +1,23 @@
+package cash.z.wallet.sdk.jni
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Test
+
+class JniConverterTest {
+
+    val converter:JniConverter = JniConverter()
+
+    @Test
+    fun testGetAddress_exists() {
+        assertNotNull(converter.getAddress("dummyseed".toByteArray()))
+    }
+
+    @Test
+    fun testGetAddress_valid() {
+        val address = converter.getAddress("dummyseed".toByteArray())
+        val expectedAddress = "ztestsapling1snmqdnfqnc407pvqw7sld8w5zxx6nd0523kvlj4jf39uvxvh7vn0hs3q38n07806dwwecqwke3t"
+        assertEquals("Invalid address", expectedAddress, address)
+    }
+
+}