How to test Encoders?

[abergmeier]

In this repo, AbstractEncoderTest is used to test MessageToByteEncoder.
Including netty-all (via Gradle), it seems like AbstractEncoderTest is not included.
So how is one supposed to best test MessageToByteEncoder?

[turnik]

Netty provides EmbeddedChannel for testing purposes, I hope the following example will answer your question.

//kotlin
class MyDecoderTest {

    @Test
    fun `test decoder`() {
        //init channel
        val channel = EmbeddedChannel(MyDecoder())

        //send data
        channel.writeInbound(1)

        //get and validate result
        val result = channel.readInbound<Int>()
        assertEquals(2, result)
    }

    @Test
    fun `test encoder using hexdump`() {
        //init channel
        val channel = EmbeddedChannel(MyEncoder())

        //send data
        channel.writeOutbound(1)
        val outboundBuf = channel.readOutbound<ByteBuf>()

        // compare with the hex string using hexdump (more human-readable)
        assertEquals("00000001", ByteBufUtil.hexDump(outboundBuf))
    }

    @Test
    fun `test encoder using another buffer`() {
        //init channel
        val channel = EmbeddedChannel(MyEncoder())

        //send data
        channel.writeOutbound(1)
        val outboundBuf = channel.readOutbound<ByteBuf>()

        //validate result
        assertEquals(4, outboundBuf.readableBytes()) //check length of buf

        val expectedBuf = channel.alloc().directBuffer()
            .writeInt(1) //create similar buf

        assertEquals(expectedBuf, outboundBuf)
    }

    @Test
    fun `test encoder using byte array`() {
        //init channel
        val channel = EmbeddedChannel(MyEncoder())

        //send data
        channel.writeOutbound(1)
        val outboundBuf = channel.readOutbound<ByteBuf>()

        //validate result
        val resultArray = ByteArray(4)
        outboundBuf.readBytes(resultArray)
        assert(byteArrayOf(0x00, 0x00, 0x00, 0x01) contentEquals  resultArray)
    }

    class MyDecoder : MessageToMessageDecoder<Int>() {
        override fun decode(ctx: ChannelHandlerContext, msg: Int, out: MutableList<Any>) {
            val newInt = msg + 1
            out.add(newInt)
        }
    }

    class MyEncoder : MessageToByteEncoder<Int>() {
        override fun encode(ctx: ChannelHandlerContext, msg: Int, out: ByteBuf) {
            //encode int message to ByteBuf
            out.writeInt(msg)
        }
    }
}

[abergmeier]

Thanks for the examples.
What I am still fuzzy about is when to use e.g. writeAndFlush vs. writeOutbound.

[chrisvest]

The writeOutbound bypasses the pipeline and directly adds output to the outbound buffer.