Split TTS playback speed regression test

Signed-off-by: John Tennant <jtennant@squareup.com>

desktop/src-tauri/src/huddle/tts.rs

@@ -920,6 +920,9 @@ fn lock_player_ops(ops: &Mutex<()>) -> MutexGuard<'_, ()> {
 
 // ── Tests ─────────────────────────────────────────────────────────────────────
 
+#[cfg(test)]
+#[path = "tts_playback_speed_tests.rs"]
+mod playback_speed_tests;
 #[cfg(test)]
 #[path = "tts_tests.rs"]
 mod tests;

desktop/src-tauri/src/huddle/tts_playback_speed_tests.rs

@@ -0,0 +1,26 @@
+use super::*;
+
+/// Regression guard: playback decoration happens after speed processing, so
+/// the fixed device cushion is never time-stretched.
+#[test]
+fn playback_speed_preserves_production_sentence_lead_in() {
+    let processed = process_complete_chunk(&vec![0.5; 2_400], 1.5, SAMPLE_RATE)
+        .expect("process synthesized model audio");
+    let mut first = true;
+    let processed =
+        build_sentence_append_buffer(&mut first, processed, 2_400, true, true);
+
+    assert_eq!(SENTENCE_LEAD_IN_SAMPLES, 480);
+    assert!(
+        processed[..SENTENCE_LEAD_IN_SAMPLES]
+            .iter()
+            .all(|&sample| sample == 0.0),
+        "the fixed device cushion must remain pure zero"
+    );
+    assert!(
+        processed[SENTENCE_LEAD_IN_SAMPLES..]
+            .iter()
+            .any(|sample| sample.abs() > 0.1),
+        "speech energy must remain after the fixed device cushion"
+    );
+}

desktop/src-tauri/src/huddle/tts_tests.rs

@@ -885,31 +885,6 @@ fn sentence_append_buffer_is_one_contiguous_source() {
     );
 }
 
-/// Regression guard: playback decoration happens after speed processing, so
-/// the fixed device cushion is never time-stretched.
-#[test]
-fn playback_speed_preserves_production_sentence_lead_in() {
-    let processed = process_complete_chunk(&vec![0.5; 2_400], 1.5, SAMPLE_RATE)
-        .expect("process synthesized model audio");
-    let mut first = true;
-    let processed =
-        build_sentence_append_buffer(&mut first, processed, 2_400, true, true);
-
-    assert_eq!(SENTENCE_LEAD_IN_SAMPLES, 480);
-    assert!(
-        processed[..SENTENCE_LEAD_IN_SAMPLES]
-            .iter()
-            .all(|&sample| sample == 0.0),
-        "the fixed device cushion must remain pure zero"
-    );
-    assert!(
-        processed[SENTENCE_LEAD_IN_SAMPLES..]
-            .iter()
-            .any(|sample| sample.abs() > 0.1),
-        "speech energy must remain after the fixed device cushion"
-    );
-}
-
 // ── clamp_to_full_scale tests ─────────────────────────────────────────────
 
 /// In-range speech audio passes through bit-exact — no gain is applied.