Add regression test for Gemma4 audio relative positional range

tests/models/gemma4/test_modeling_gemma4.py

@@ -270,6 +270,34 @@ def test_num_layers_is_small(self):
     def test_generate_from_random_inputs_embeds(self):
         pass
 
+    def test_audio_rel_pos_encoding_uses_context_size_from_config(self):
+        from transformers.models.gemma4.configuration_gemma4 import Gemma4AudioConfig
+        from transformers.models.gemma4.modeling_gemma4 import Gemma4AudioRelPositionalEncoding
+
+        config = Gemma4AudioConfig(
+            hidden_size=32,
+            attention_chunk_size=6,
+            attention_context_left=5,
+            attention_context_right=1,
+            use_clipped_linears=False,
+        )
+
+        module = Gemma4AudioRelPositionalEncoding(config)
+        hidden_states = torch.zeros(1, 3, config.hidden_size)
+
+        pos = module(hidden_states)
+
+        context_size = config.attention_chunk_size + config.attention_context_left - 1 + config.attention_context_right
+        expected_len = context_size // 2 + 1
+
+        self.assertEqual(pos.shape, (1, expected_len, config.hidden_size))
+
+        position_ids = torch.arange(context_size // 2, -1, -1, device=hidden_states.device)[..., None]
+        scaled_time = position_ids * module.inv_timescales.to(device=hidden_states.device)
+        expected = torch.cat([torch.sin(scaled_time), torch.cos(scaled_time)], dim=-1).to(hidden_states.dtype)
+
+        torch.testing.assert_close(pos, expected)
+
 
 class Gemma4Vision2TextModelTester:
     def __init__(