Tests for #11283 (#12322)

Added tests for #11283. The itEncodesNullObjects test fails with the branch before the merge and succeeds with the master branch

Author: rafern

shell/platform/android/BUILD.gn

@@ -416,6 +416,7 @@ action("robolectric_tests") {
     "test/io/flutter/embedding/engine/RenderingComponentTest.java",
     "test/io/flutter/embedding/engine/renderer/FlutterRendererTest.java",
     "test/io/flutter/embedding/engine/systemchannels/PlatformChannelTest.java",
+    "test/io/flutter/plugin/common/StandardMessageCodecTest.java",
     "test/io/flutter/plugin/platform/SingleViewPresentationTest.java",
     "test/io/flutter/util/PreconditionsTest.java",
   ]

shell/platform/android/test/io/flutter/FlutterTestSuite.java

@@ -15,6 +15,7 @@
 import io.flutter.embedding.engine.RenderingComponentTest;
 import io.flutter.embedding.engine.renderer.FlutterRendererTest;
 import io.flutter.embedding.engine.systemchannels.PlatformChannelTest;
+import io.flutter.plugin.common.StandardMessageCodecTest;
 import io.flutter.plugin.platform.SingleViewPresentationTest;
 import io.flutter.util.PreconditionsTest;
 
@@ -29,6 +30,7 @@
     PlatformChannelTest.class,
     PreconditionsTest.class,
     RenderingComponentTest.class,
+    StandardMessageCodecTest.class,
     SingleViewPresentationTest.class,
     SmokeTest.class,
 })

shell/platform/android/test/io/flutter/plugin/common/StandardMessageCodecTest.java

@@ -0,0 +1,80 @@
+package io.flutter.plugin.common;
+
+import io.flutter.plugin.common.StandardMessageCodec;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+
+import static org.junit.Assert.assertEquals;
+
+@Config(manifest=Config.NONE)
+@RunWith(RobolectricTestRunner.class)
+public class StandardMessageCodecTest {
+    // Data types defined as per StandardMessageCodec.Java
+    // XXX Please consider exposing these so that tests can access them
+    private static final byte NULL = 0;
+    private static final byte TRUE = 1;
+    private static final byte FALSE = 2;
+    private static final byte INT = 3;
+    private static final byte LONG = 4;
+    private static final byte BIGINT = 5;
+    private static final byte DOUBLE = 6;
+    private static final byte STRING = 7;
+    private static final byte BYTE_ARRAY = 8;
+    private static final byte INT_ARRAY = 9;
+    private static final byte LONG_ARRAY = 10;
+    private static final byte DOUBLE_ARRAY = 11;
+    private static final byte LIST = 12;
+    private static final byte MAP = 13;
+
+    @Test
+    public void itEncodesNullLiterals() {
+        // Setup message codec
+        StandardMessageCodec codec = new StandardMessageCodec();
+        
+        // Attempt to encode message with a null literal inside a list
+        // A list with a null is used instead of just a null literal because if
+        // only null is encoded, then no message is returned; null is returned instead
+        ArrayList<Object> messageContent = new ArrayList();
+        messageContent.add(null);
+        ByteBuffer message = codec.encodeMessage(messageContent);
+        message.flip();
+        ByteBuffer expected = ByteBuffer.allocateDirect(3);
+        expected.put(new byte[]{LIST, 1, NULL});
+        expected.flip();
+        assertEquals(expected, message);
+    }
+
+    @Test
+    public void itEncodesNullObjects() {
+        // An example class that equals null
+        class ExampleNullObject {
+            @Override
+            public boolean equals(Object other) {
+                return other == null || other == this;
+            }
+            
+            @Override
+            public int hashCode() {
+                return 0;
+            }
+        }
+        
+        // Setup message codec
+        StandardMessageCodec codec = new StandardMessageCodec();
+        
+        // Same as itEncodesNullLiterals but with objects that equal null instead
+        ArrayList<Object> messageContent = new ArrayList();
+        messageContent.add(new ExampleNullObject());
+        ByteBuffer message = codec.encodeMessage(messageContent);
+        message.flip();
+        ByteBuffer expected = ByteBuffer.allocateDirect(3);
+        expected.put(new byte[]{LIST, 1, NULL});
+        expected.flip();
+        assertEquals(expected, message);
+    }
+}