fix: create deflater in DEFLATER mode in CompressionFilter

[ppkarwasz]

What

Due to a copy/paste error in #52 CompressionFilter.onPreAdd() built the outbound deflater with Zlib.MODE_INFLATER instead of MODE_DEFLATER, so every outbound write threw IllegalStateException ("not initialized as DEFLATER") from Zlib.deflate(). Outbound compression was completely broken.

Why it went unnoticed

CompressionFilterTest was @Ignored with its body commented out (it depended on EasyMock's removed MockControl API), so CompressionFilter had no live coverage. ZlibTest only exercises Zlib directly, never going through onPreAdd().

Changes

• One-line fix: deflater is now created with MODE_DEFLATER.
• Rewrote CompressionFilterTest with Mockito, replacing the unused EasyMock dependency (Mockito is already managed in the root pom and used in mina-core).
• Added coverage for onPreAdd(): a compress/decompress round trip, and a guard that the deflater and inflater are not swapped.

Both new tests fail against the buggy code with the expected IllegalStateException, and pass with the fix.

[elecharny]

Thanks a lot Piotr,

I was trying to reactivate the test that was commented (mostly due to the fact we were using an old version of easymock, and we just were too lazy to port it, which was a VERY bad idea...).

Would this test been active, the original copy/paste mistake would never have been a problem :/

[elecharny]

Ok, seems correct for 2.2.X. However I won't be able to backport the test because mockito 5 requires a Java version >= 11.

Not such a big deal, as we can rely on 2.2.X for such tests, and backport the code but the test in 2.1.X and 2.0.X.

[elecharny]

Hi @ppkarwasz, I don't think we need to pass the size parameters for the deflater:

        Zlib deflater = new Zlib(compressionLevel, Zlib.MODE_DEFLATER);

instead of

        Zlib deflater = new Zlib(compressionLevel, Zlib.MODE_DEFLATER, maxDecompressedSize, 
                maxDecompressRatio, decompressRatioMinSize);

[ppkarwasz]

Mockito 4 should work IIRC.

[ppkarwasz]

I don't think we need to pass the size parameters for the deflater:

Yes, I added it for symmetry and in the previous PR I pushed the symmetry one step too far… 😆

[elecharny]

@ppkarwasz works like a charm with mockito 4 on 2.1.X branch! I'm currently cutting the 3 releases, we should be good to go this week-end. Thanks for the help!