Implemented test for public constructor (#3153)

lib/android/app/src/test/java/com/reactnativenavigation/react/ReactGatewayTest.java

@@ -0,0 +1,27 @@
+package com.reactnativenavigation.react;
+
+import com.reactnativenavigation.BaseTest;
+
+import org.junit.Test;
+import org.robolectric.RuntimeEnvironment;
+
+public class ReactGatewayTest extends BaseTest {
+
+    @Override
+    public void beforeEach() {
+        super.beforeEach();
+    }
+
+    /**
+     * This is to make sure that the constructor that takes a host remains public as per
+     * reasons described on this ticket:
+     * https://github.com/wix/react-native-navigation/issues/3145
+     * Exception comes from SoLoader.init so we simply ignore it as it's not related to this test
+     */
+    @Test(expected = RuntimeException.class)
+    public void testPublicConstructor() {
+        NavigationReactNativeHost host = new NavigationReactNativeHost(RuntimeEnvironment.application, false, null);
+        new ReactGateway(RuntimeEnvironment.application, false, host);
+    }
+
+}