New tests for BasicFieldImageView image from /assets/. (google#444)

Tests for google#442.

blocklytest/src/androidTest/java/com/google/blockly/android/ui/fieldview/BasicFieldImageViewTest.java

@@ -0,0 +1,52 @@
+package com.google.blockly.android.ui.fieldview;
+
+import android.content.Context;
+
+import com.google.blockly.android.MockitoAndroidTestCase;
+
+import org.mockito.AdditionalAnswers;
+import org.mockito.Mockito;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * Tests for {@link BasicFieldImageView}.
+ */
+public class BasicFieldImageViewTest extends MockitoAndroidTestCase {
+    Context mMockContext;
+
+    BasicFieldImageView mImageFieldView;
+
+    @Override
+    public void setUp() throws Exception {
+        super.setUp();
+
+        mMockContext = Mockito.mock(Context.class, AdditionalAnswers.delegatesTo(getContext()));
+
+        mImageFieldView = new BasicFieldImageView(mMockContext);
+    }
+
+    public void testImageSourceFromAssets() throws IOException {
+        InputStream in = null;
+        try {
+            in = mImageFieldView.getStreamForSource("localIcon.png");
+            assertNotEmpty(in);
+            in.close();
+
+            in = mImageFieldView.getStreamForSource("/localIcon.png");
+            assertNotEmpty(in);
+            in.close();
+
+            in = mImageFieldView.getStreamForSource("file:///android_assets/localIcon.png");
+            assertNotEmpty(in);
+        } finally {
+            in.close();
+        }
+    }
+
+    private void assertNotEmpty(InputStream in) throws IOException {
+        assertNotNull(in);
+        assertTrue(in.available() > 0);
+    }
+}