// TestRequired.b and TestRequired.c are not set.
TestRequired partialMessage = TestRequired.newBuilder()
.setA(1).buildPartial();
// parsePartialFrom should pass.
byte[] data = partialMessage.toByteArray();
assertEquals(partialMessage, parser.parsePartialFrom(data));
assertEquals(partialMessage, parser.parsePartialFrom(
partialMessage.toByteString()));
assertEquals(partialMessage, parser.parsePartialFrom(
new ByteArrayInputStream(data)));