feat: Add ffmpeg remuxing for faststart

server/tests/transcribe_test.rs

@@ -0,0 +1,45 @@
+use std::path::PathBuf;
+
+use doctate_server::transcribe::ffmpeg::remux_faststart;
+
+fn fixture(name: &str) -> PathBuf {
+    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/fixtures")
+        .join(name)
+}
+
+#[tokio::test]
+async fn ffmpeg_remux_produces_valid_output() {
+    let input = fixture("sample.m4a");
+    assert!(input.exists(), "fixture missing: {}", input.display());
+
+    let output = remux_faststart(&input)
+        .await
+        .expect("remux failed");
+
+    let meta = std::fs::metadata(output.path()).expect("output missing");
+    assert!(meta.len() > 0, "output file is empty");
+
+    // Sanity check: ffprobe should still recognize it as an m4a/mp4 container.
+    let probe = std::process::Command::new("ffprobe")
+        .arg("-hide_banner")
+        .arg("-loglevel")
+        .arg("error")
+        .arg("-show_entries")
+        .arg("format=format_name")
+        .arg("-of")
+        .arg("default=nw=1:nk=1")
+        .arg(output.path())
+        .output()
+        .expect("ffprobe spawn failed");
+    assert!(probe.status.success(), "ffprobe failed");
+    let fmt = String::from_utf8_lossy(&probe.stdout);
+    assert!(fmt.contains("mp4") || fmt.contains("m4a"), "unexpected format: {fmt}");
+}
+
+#[tokio::test]
+async fn ffmpeg_remux_fails_on_missing_input() {
+    let input = PathBuf::from("/nonexistent/does-not-exist.m4a");
+    let result = remux_faststart(&input).await;
+    assert!(result.is_err(), "expected error for missing input");
+}