From 25a4d7ffab0947ed84973bcf9a12c9fa337296ef Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 29 Dec 2025 21:16:11 -1000
Subject: [PATCH] tweak

---
 tests/unit_tests/test_main.py | 65 +++++++++++++++++++++++++++++------
 1 file changed, 55 insertions(+), 10 deletions(-)

diff --git a/tests/unit_tests/test_main.py b/tests/unit_tests/test_main.py
index 0b88e7c623..1db7944653 100644
--- a/tests/unit_tests/test_main.py
+++ b/tests/unit_tests/test_main.py
@@ -2811,15 +2811,20 @@ def test_compile_program_no_build_info_when_json_missing_keys(
 # Tests for run_miniterm serial log batching
 
 
+# Sentinel to signal end of mock serial data (raises SerialException)
+MOCK_SERIAL_END = object()
+
+
 class MockSerial:
     """Mock serial port for testing run_miniterm."""
 
-    def __init__(self, chunks: list[bytes]) -> None:
+    def __init__(self, chunks: list[bytes | object]) -> None:
         """Initialize with a list of chunks to return from read().
 
         Args:
             chunks: List of byte chunks to return sequentially.
-                    Empty bytes at the end signal end of data.
+                    Use MOCK_SERIAL_END sentinel to signal end of data.
+                    Empty bytes b"" simulate timeout (no data available).
         """
         self.chunks = list(chunks)
         self.chunk_index = 0
@@ -2841,7 +2846,10 @@ class MockSerial:
     def in_waiting(self) -> int:
         """Return number of bytes available."""
         if self.chunk_index < len(self.chunks):
-            return len(self.chunks[self.chunk_index])
+            chunk = self.chunks[self.chunk_index]
+            if chunk is MOCK_SERIAL_END:
+                return 0
+            return len(chunk)  # type: ignore[arg-type]
         return 0
 
     def read(self, size: int = 1) -> bytes:
@@ -2849,12 +2857,12 @@ class MockSerial:
         if self.chunk_index < len(self.chunks):
             chunk = self.chunks[self.chunk_index]
             self.chunk_index += 1
-            if not chunk:
-                # Empty chunk means we're done - simulate end
+            if chunk is MOCK_SERIAL_END:
+                # Sentinel means we're done - simulate port closed
                 import serial
 
                 raise serial.SerialException("Port closed")
-            return chunk
+            return chunk  # type: ignore[return-value]
         import serial
 
         raise serial.SerialException("Port closed")
@@ -2868,7 +2876,7 @@ def test_run_miniterm_batches_lines_with_same_timestamp(
     # This is how data arrives over USB - many lines at once
     chunk = b"[I][app:100]: Line 1\r\n[I][app:100]: Line 2\r\n[I][app:100]: Line 3\r\n"
 
-    mock_serial = MockSerial([chunk, b""])
+    mock_serial = MockSerial([chunk, MOCK_SERIAL_END])
 
     config = {
         CONF_LOGGER: {
@@ -2906,7 +2914,7 @@ def test_run_miniterm_different_chunks_different_timestamps(
     chunk1 = b"[I][app:100]: Chunk 1 Line\r\n"
     chunk2 = b"[I][app:100]: Chunk 2 Line\r\n"
 
-    mock_serial = MockSerial([chunk1, chunk2, b""])
+    mock_serial = MockSerial([chunk1, chunk2, MOCK_SERIAL_END])
 
     config = {
         CONF_LOGGER: {
@@ -2936,7 +2944,7 @@ def test_run_miniterm_handles_split_lines() -> None:
     chunk1 = b"[I][app:100]: Start of "
     chunk2 = b"line\r\n"
 
-    mock_serial = MockSerial([chunk1, chunk2, b""])
+    mock_serial = MockSerial([chunk1, chunk2, MOCK_SERIAL_END])
 
     config = {
         CONF_LOGGER: {
@@ -2974,7 +2982,7 @@ def test_run_miniterm_backtrace_state_maintained() -> None:
         b"<<<stack<<<\r\n"
     )
 
-    mock_serial = MockSerial([backtrace_chunk, b""])
+    mock_serial = MockSerial([backtrace_chunk, MOCK_SERIAL_END])
 
     config = {
         CONF_LOGGER: {
@@ -3028,6 +3036,43 @@ def test_run_miniterm_backtrace_state_maintained() -> None:
     assert backtrace_states[3][1] is True
 
 
+def test_run_miniterm_handles_empty_reads(
+    capfd: CaptureFixture[str],
+) -> None:
+    """Test that empty reads (timeouts) are handled correctly.
+
+    When read() returns empty bytes, the code should continue waiting
+    for more data without processing anything.
+    """
+    # Simulate: empty read (timeout), then data, then empty read, then end
+    chunk = b"[I][app:100]: Test line\r\n"
+
+    mock_serial = MockSerial([b"", chunk, b"", MOCK_SERIAL_END])
+
+    config = {
+        CONF_LOGGER: {
+            CONF_BAUD_RATE: 115200,
+            "deassert_rts_dtr": False,
+        }
+    }
+    args = MockArgs()
+
+    with (
+        patch("serial.Serial", return_value=mock_serial),
+        patch.object(platformio_api, "process_stacktrace") as mock_bt,
+    ):
+        mock_bt.return_value = False
+        result = run_miniterm(config, "/dev/ttyUSB0", args)
+
+    assert result == 0
+
+    captured = capfd.readouterr()
+    lines = [line for line in captured.out.strip().split("\n") if line]
+    # Should have exactly one line despite empty reads
+    assert len(lines) == 1
+    assert "Test line" in lines[0]
+
+
 def test_run_miniterm_no_logger_returns_early(
     caplog: pytest.LogCaptureFixture,
 ) -> None: