diff --git a/tests/decoders/test_jsonl.py b/tests/decoders/test_jsonl.py
new file mode 100644
index 00000000..a14a93e6
--- /dev/null
+++ b/tests/decoders/test_jsonl.py
@@ -0,0 +1,88 @@
+from __future__ import annotations
+
+from typing import Any, Iterator, AsyncIterator
+from typing_extensions import TypeVar
+
+import httpx
+import pytest
+
+from gitpod._decoders.jsonl import JSONLDecoder, AsyncJSONLDecoder
+
+_T = TypeVar("_T")
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("sync", [True, False], ids=["sync", "async"])
+async def test_basic(sync: bool) -> None:
+    def body() -> Iterator[bytes]:
+        yield b'{"foo":true}\n'
+        yield b'{"bar":false}\n'
+
+    iterator = make_jsonl_iterator(
+        content=body(),
+        sync=sync,
+        line_type=object,
+    )
+
+    assert await iter_next(iterator) == {"foo": True}
+    assert await iter_next(iterator) == {"bar": False}
+
+    await assert_empty_iter(iterator)
+
+
+@pytest.mark.parametrize("sync", [True, False], ids=["sync", "async"])
+async def test_new_lines_in_json(
+    sync: bool,
+) -> None:
+    def body() -> Iterator[bytes]:
+        yield b'{"content":"Hello, world!\\nHow are you doing?"}'
+
+    iterator = make_jsonl_iterator(content=body(), sync=sync, line_type=object)
+
+    assert await iter_next(iterator) == {"content": "Hello, world!\nHow are you doing?"}
+
+
+@pytest.mark.parametrize("sync", [True, False], ids=["sync", "async"])
+async def test_multi_byte_character_multiple_chunks(
+    sync: bool,
+) -> None:
+    def body() -> Iterator[bytes]:
+        yield b'{"content":"'
+        # bytes taken from the string 'известни' and arbitrarily split
+        # so that some multi-byte characters span multiple chunks
+        yield b"\xd0"
+        yield b"\xb8\xd0\xb7\xd0"
+        yield b"\xb2\xd0\xb5\xd1\x81\xd1\x82\xd0\xbd\xd0\xb8"
+        yield b'"}\n'
+
+    iterator = make_jsonl_iterator(content=body(), sync=sync, line_type=object)
+
+    assert await iter_next(iterator) == {"content": "известни"}
+
+
+async def to_aiter(iter: Iterator[bytes]) -> AsyncIterator[bytes]:
+    for chunk in iter:
+        yield chunk
+
+
+async def iter_next(iter: Iterator[_T] | AsyncIterator[_T]) -> _T:
+    if isinstance(iter, AsyncIterator):
+        return await iter.__anext__()
+    return next(iter)
+
+
+async def assert_empty_iter(decoder: JSONLDecoder[Any] | AsyncJSONLDecoder[Any]) -> None:
+    with pytest.raises((StopAsyncIteration, RuntimeError)):
+        await iter_next(decoder)
+
+
+def make_jsonl_iterator(
+    content: Iterator[bytes],
+    *,
+    sync: bool,
+    line_type: type[_T],
+) -> JSONLDecoder[_T] | AsyncJSONLDecoder[_T]:
+    if sync:
+        return JSONLDecoder(line_type=line_type, raw_iterator=content, http_response=httpx.Response(200))
+
+    return AsyncJSONLDecoder(line_type=line_type, raw_iterator=to_aiter(content), http_response=httpx.Response(200))