[android] add basic tests for auto generated java lib

When the SWIG interface file (commissioner.i) is updated, the generated
java library API may be broken. There are currently no tests to guard
this. This commit adds a basic androidTest for this purpose. Note that
an Android rather than junit test is added because the test case depends
on an JNI library.

android/openthread_commissioner/service/build.gradle

@@ -81,7 +81,7 @@ dependencies {
     implementation 'com.google.android.gms:play-services-vision:20.1.3+'
     implementation 'com.google.android.gms:play-services-threadnetwork:16.0.0'
     implementation 'com.google.android.material:material:1.2.1'
-    testImplementation 'junit:junit:4.+'
+    androidTestImplementation 'com.google.truth:truth:1.4.4'
     androidTestImplementation 'androidx.test.ext:junit:1.1.5'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.0'
 }

android/openthread_commissioner/service/src/androidTest/java/io/openthread/commissioner/ActiveOperationalDatasetTest.java

@@ -0,0 +1,34 @@
+package io.openthread.commissioner;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import java.util.stream.Collectors;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public final class ActiveOperationalDatasetTest {
+  @Test
+  public void channelMask_valuesAreCorrect() {
+    ActiveOperationalDataset dataset = new ActiveOperationalDataset();
+    ChannelMaskEntry entry1 = new ChannelMaskEntry();
+    entry1.setPage((short) 0);
+    entry1.setMasks(new ByteArray(new byte[] {0x01, 0x02, 0x03, 0x04}));
+    ChannelMaskEntry entry2 = new ChannelMaskEntry();
+    entry2.setPage((short) 1);
+    entry2.setMasks(new ByteArray(new byte[] {0x05, 0x06, 0x07, 0x08}));
+    ChannelMask maskEntries = new ChannelMask();
+    maskEntries.add(entry1);
+    maskEntries.add(entry2);
+    dataset.setChannelMask(maskEntries);
+
+    assertThat(dataset.getChannelMask()).hasSize(2);
+    assertThat(dataset.getChannelMask().get(0).getPage()).isEqualTo(0);
+    assertThat(dataset.getChannelMask().get(0).getMasks().stream().collect(Collectors.toList()))
+        .containsExactly((byte) 0x01, (byte) 0x02, (byte) 0x03, (byte) 0x04);
+    assertThat(dataset.getChannelMask().get(1).getPage()).isEqualTo(1);
+    assertThat(dataset.getChannelMask().get(1).getMasks().stream().collect(Collectors.toList()))
+        .containsExactly((byte) 0x05, (byte) 0x06, (byte) 0x07, (byte) 0x08);
+  }
+}