Add StreamLineReader with unit tests

tests/test_stream_line_reader.py

@@ -0,0 +1,52 @@
+from unittest.mock import MagicMock
+
+import pytest
+
+from galaxy.reader import StreamLineReader
+from galaxy.unittest.mock import AsyncMock
+
+@pytest.fixture()
+def stream_reader():
+    reader = MagicMock()
+    reader.read = AsyncMock()
+    return reader
+
+@pytest.fixture()
+def read(stream_reader):
+    return stream_reader.read
+
+@pytest.fixture()
+def reader(stream_reader):
+    return StreamLineReader(stream_reader)
+
+@pytest.mark.asyncio
+async def test_message(reader, read):
+    read.return_value = b"a\n"
+    assert await reader.readline() == b"a"
+    read.assert_called_once()
+
+@pytest.mark.asyncio
+async def test_separate_messages(reader, read):
+    read.side_effect = [b"a\n", b"b\n"]
+    assert await reader.readline() == b"a"
+    assert await reader.readline() == b"b"
+    assert read.call_count == 2
+
+@pytest.mark.asyncio
+async def test_connected_messages(reader, read):
+    read.return_value = b"a\nb\n"
+    assert await reader.readline() == b"a"
+    assert await reader.readline() == b"b"
+    read.assert_called_once()
+
+@pytest.mark.asyncio
+async def test_cut_message(reader, read):
+    read.side_effect = [b"a", b"b\n"]
+    assert await reader.readline() == b"ab"
+    assert read.call_count == 2
+
+@pytest.mark.asyncio
+async def test_half_message(reader, read):
+    read.side_effect = [b"a", b""]
+    assert await reader.readline() == b""
+    assert read.call_count == 2