craft-audio: review fixes, round 16 (#442)

The Ogg track tests no longer depend on chance. Each writes its file
until the serial numbers are in the order it asks for, in both orders,
so the reversed order that told the old code apart always runs. A file
this ffmpeg cannot write goes through `skip`, which fails the test when
oracles are required.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/audio/src/write/flac/oracle_tests.rs

@@ -266,21 +266,35 @@ fn ogg_flac_reads_the_mask_comment() {
     }
 }
 
-/// Two streams in an Ogg file written by ffmpeg, which picks their serial numbers at random. The
-/// tests below write each file a few times, so that both serial orders occur.
+/// Two streams in an Ogg file written by ffmpeg, whose serial numbers are in file order or in
+/// `reversed` order. ffmpeg picks them at random, so this writes the file until the order occurs;
+/// symphonia orders tracks by serial, so the reversed order is the one that tells them apart.
+/// `None` after `skip` when this ffmpeg cannot write the file.
 #[cfg(feature = "symphonia")]
-fn two_ogg_streams(ff: &Path, name: &str, args: &[&str]) -> Option<Vec<u8>> {
+fn two_ogg_streams(ff: &Path, name: &str, args: &[&str], reversed: bool) -> Option<Vec<u8>> {
     let path = common::fixture_subdir("flac").join(format!("{name}.ogg"));
-    let status = Command::new(ff)
-        .args(["-v", "error", "-y", "-f", "lavfi", "-i", "aevalsrc=0|0|0|0:c=4c:d=0.1:s=48000"])
-        .args(["-f", "lavfi", "-i", "aevalsrc=0|0|0|0:c=4c:d=0.1:s=44100"])
-        .args(["-map", "0", "-map", "1"])
-        .args(args)
-        .args(["-f", "ogg"])
-        .arg(&path)
-        .status()
-        .unwrap();
-    status.success().then(|| std::fs::read(&path).unwrap())
+    for attempt in 0..64 {
+        let status = Command::new(ff)
+            .args(["-v", "error", "-y", "-f", "lavfi", "-i", "aevalsrc=0|0|0|0:c=4c:d=0.1:s=48000"])
+            .args(["-f", "lavfi", "-i", "aevalsrc=0|0|0|0:c=4c:d=0.1:s=44100"])
+            .args(["-map", "0", "-map", "1"])
+            .args(args)
+            .args(["-f", "ogg"])
+            .arg(&path)
+            .status()
+            .unwrap();
+        if !status.success() {
+            return common::skip(&format!("this ffmpeg cannot write {name}"));
+        }
+        let bytes = std::fs::read(&path).unwrap();
+        let file = craft_media::ogg::open(bytes.as_slice()).unwrap();
+        assert_eq!(file.streams.len(), 2, "{name}");
+        if (file.streams[0].serial > file.streams[1].serial) == reversed {
+            return Some(bytes);
+        }
+        assert!(attempt < 63, "{name}: 64 files with their serial numbers in one order");
+    }
+    None
 }
 
 /// A track index means the same stream in `tracks`, `probe` and `decode`: the file's order. Each
@@ -291,8 +305,8 @@ fn ogg_flac_tracks_are_in_file_order_with_their_own_mask_comments() {
     use crate::{ChannelLayout, DecodeOptions};
     let Some(ff) = ffmpeg() else { return };
     let args = ["-c:a", "flac", "-metadata:s:a:0", "WAVEFORMATEXTENSIBLE_CHANNEL_MASK=0x0107"];
-    for _ in 0..8 {
-        let bytes = two_ogg_streams(&ff, "ogg-one-mask", &args).unwrap();
+    for reversed in [false, true] {
+        let Some(bytes) = two_ogg_streams(&ff, "ogg-one-mask", &args, reversed) else { return };
         let rates: Vec<_> = crate::tracks(&bytes, None).unwrap().iter().map(|t| t.sample_rate).collect();
         assert_eq!(rates, [Some(48_000), Some(44_100)]);
         for (track, rate, layout) in [(0, 48_000, ChannelLayout::from_mask(0x107)), (1, 44_100, ChannelLayout::default_for(4))] {
@@ -313,8 +327,8 @@ fn ogg_flac_before_opus_is_the_first_track() {
     use crate::CodecId;
     let Some(ff) = ffmpeg() else { return };
     let args = ["-c:a:0", "flac", "-c:a:1", "libopus", "-ac:a:1", "2"];
-    for _ in 0..8 {
-        let Some(bytes) = two_ogg_streams(&ff, "ogg-flac-opus", &args) else { return };
+    for reversed in [false, true] {
+        let Some(bytes) = two_ogg_streams(&ff, "ogg-flac-opus", &args, reversed) else { return };
         assert_eq!(crate::tracks(&bytes, None).unwrap()[0].codec, CodecId::Flac);
         assert_eq!(crate::decode(&bytes, None).unwrap().0.codec, CodecId::Flac);
     }