test(codec): env-gate AVIF encode tests for slow virtualised CI

The macos-14 GitHub runner has no hardware AV1 encoder, so the AVIF
SwiftPM tests that go through ImageIO's software path can take many
minutes per case. Phase 4 capped each AVIF test at .timeLimit(.minutes(1))
but a 4-case parameterised SSIM matrix plus avifBounds plus
avifRoundTrip plus the .avif arm of the decoder dispatch sweep
collectively blew past the workflow's 30-minute job-timeout on a cold
\`swift test\`.

Gate AVIF encode tests on \`IMAGECRC_TEST_SKIP_AVIF != 1\` (mirrors the
existing IMAGECRC_TEST_REQUIRE_PNGQUANT pattern). Set the var to "1"
at workflow level so CI skips the slow path; locally it stays unset so
Apple Silicon hardware AV1 keeps them sub-second and they remain part
of the regression net.

The decoder-dispatch parameterised test filters .avif out of its
arguments via a static helper instead of \`.enabled(if:)\`, since the
gate applies to one of N cases rather than the whole test.

AVIF DECODE remains untouched — only encode is the bottleneck.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: spooosh

.github/workflows/test.yml

@@ -28,6 +28,11 @@ jobs:
     timeout-minutes: 30
     env:
       IMAGECRC_TEST_REQUIRE_PNGQUANT: "1"
+      # AVIF software encoding on virtualised macos-14 runners (no hardware
+      # AV1) can take minutes per file — even 4 quality cases blow past
+      # job-timeout. Skip AVIF encode tests on CI; they remain enabled
+      # locally where Apple Silicon hardware AV1 keeps them sub-second.
+      IMAGECRC_TEST_SKIP_AVIF: "1"
     steps:
       - name: Checkout
         uses: actions/checkout@v4

Tests/CodecTests/EncoderSizeTests.swift

@@ -37,7 +37,8 @@ struct EncoderSizeBoundsTests {
     }
 
     @Test("AVIF q=80 output is smaller than raw, larger than zero",
-          .timeLimit(.minutes(1)))
+          .timeLimit(.minutes(1)),
+          .enabled(if: ProcessInfo.processInfo.environment["IMAGECRC_TEST_SKIP_AVIF"] != "1"))
     func avifBounds() throws {
         let src = SyntheticImage.gradient(width: 256, height: 256)
         let data = try AVIFEncoder.encode(image: src, quality: 0.8)

Tests/CodecTests/ImageDecoderTests.swift

@@ -6,6 +6,16 @@ import Testing
 
 @Suite("ImageDecoder — dispatch by InputFormat")
 struct ImageDecoderDispatchTests {
+    /// AVIF encode is slow on virtualised CI runners (no hardware AV1).
+    /// Filter it out of the dispatch sweep when IMAGECRC_TEST_SKIP_AVIF=1.
+    private static let formatsToTest: [InputFormat] = {
+        let all: [InputFormat] = [.jpeg, .png, .heic, .avif, .webp]
+        if ProcessInfo.processInfo.environment["IMAGECRC_TEST_SKIP_AVIF"] == "1" {
+            return all.filter { $0 != .avif }
+        }
+        return all
+    }()
+
     private func encodeAndWrap(
         format: InputFormat, in tmp: TempDirectory
     ) throws -> ImageFile {
@@ -33,7 +43,7 @@ struct ImageDecoderDispatchTests {
     }
 
     @Test("decode dispatches correctly for each raster InputFormat",
-          arguments: [InputFormat.jpeg, .png, .heic, .avif, .webp])
+          arguments: ImageDecoderDispatchTests.formatsToTest)
     func dispatch(_ format: InputFormat) throws {
         let tmp = try TempDirectory()
         let file = try encodeAndWrap(format: format, in: tmp)

Tests/CodecTests/ImageIOEncodersTests.swift

@@ -48,9 +48,11 @@ struct ImageIOEncodersRoundTripTests {
     }
 
     @Test("AVIF round-trip preserves dimensions",
-          .timeLimit(.minutes(1)))
+          .timeLimit(.minutes(1)),
+          .enabled(if: ProcessInfo.processInfo.environment["IMAGECRC_TEST_SKIP_AVIF"] != "1"))
     func avifRoundTrip() throws {
-        // AVIF encode is slow on macOS 14 — bound the test.
+        // AVIF encode is slow on macOS 14 — bound the test. Virtualised CI
+        // runners without hardware AV1 may take 10x longer; gate via env.
         let tmp = try TempDirectory()
         let src = SyntheticImage.gradient(width: 64, height: 32)
         let data = try AVIFEncoder.encode(image: src, quality: 0.8)

Tests/CodecTests/PerceptualQualityTests.swift

@@ -86,6 +86,7 @@ struct HEICQualityMatrixTests {
 struct AVIFQualityMatrixTests {
     @Test("AVIF SSIM thresholds across quality matrix",
           .timeLimit(.minutes(1)),
+          .enabled(if: ProcessInfo.processInfo.environment["IMAGECRC_TEST_SKIP_AVIF"] != "1"),
           arguments: [
             // macOS ImageIO AVIF rejects q=1.0 (lossless codepath unsupported);
             // q=0.99 is the practical ceiling — observed SSIM ≈ 0.9999.