Clean up echo kernel handling and update readme (#22)

Author: blink1073

README.md

@@ -31,6 +31,26 @@ To use a plugin, add it to the `pytest_plugins` list in the `conftest.py` of you
 pytest_plugins = ["pytest_jupyter.jupyter_server"]
 ```
 
+This library includes an `echo_kernel`, which is useful to speed up testing.
+You must have either `"pytest-jupyter[server]"` or `"pytest-jupyter[client]"`
+installed to use the echo kernel.
+
+The `pytest_jupyter.jupyter_client` plugin provides an installed
+`echo_kernel_spec` as a fixture, and a `start_kernel` fixture
+that provides a factory function that starts a kernel using the `echo` kernel
+by default.
+
+The server fixures use the echo kernel by default.  To override this behavior,
+override the `jp_server_config` fixture and add the following config:
+
+```json
+{
+    "MultiKernelManager": {
+        "default_kernel_name": "<desired_kernel_name"
+    }
+}
+```
+
 All fixtures inside the plugin (e.g. jupyter_server) will be available to all of your project's unit tests. You can use a fixtures by passing it as an argument to your unit test function:
 
 ```python

pyproject.toml

@@ -96,7 +96,7 @@ filterwarnings= [
   # Fail on warnings
   "error",
   # TODO: from jupyter_server
-  "always:unclosed <socket.socket:ResourceWarning",
+  "always:unclosed <socket.socket:ResourceWarning"
 ]
 
 [tool.coverage.report]

pytest_jupyter/jupyter_client.py

@@ -54,23 +54,24 @@ def zmq_context():
 
 
 @pytest.fixture
-async def start_kernel(kernel_spec):
-    km = None
-    kc = None
+async def start_kernel(echo_kernel_spec):
+    kms = []
+    kcs = []
 
     async def inner(kernel_name="echo", **kwargs):
-        nonlocal km, kc
         km, kc = await start_new_async_kernel(kernel_name=kernel_name, **kwargs)
+        kms.append(km)
+        kcs.append(kc)
         return km, kc
 
     yield inner
 
-    if kc and km:
+    for kc in kcs:
         kc.stop_channels()
+
+    for km in kms:
         await km.shutdown_kernel(now=True)
         assert km.context.closed
-        km.context.destroy()
-        km.context.term()
 
 
 @pytest.fixture()
@@ -79,7 +80,7 @@ def kernel_dir():
 
 
 @pytest.fixture
-def kernel_spec(kernel_dir):
+def echo_kernel_spec(kernel_dir):
     test_dir = Path(kernel_dir) / "echo"
     test_dir.mkdir(parents=True, exist_ok=True)
     argv = [sys.executable, "-m", "pytest_jupyter.echo_kernel", "-f", "{connection_file}"]

pytest_jupyter/jupyter_server.py

@@ -45,7 +45,7 @@
     )
 
 
-from .jupyter_client import kernel_spec  # noqa
+from .jupyter_client import echo_kernel_spec  # noqa
 from .utils import mkdir
 
 # List of dependencies needed for this plugin.
@@ -102,13 +102,14 @@ async def get_server():
 def jp_server_config():
     """Allows tests to setup their specific configuration values."""
     if is_v2:
-        return Config(
-            {
+        config = {
+            "ServerApp": {
                 "jpserver_extensions": {"jupyter_server_terminals": True},
             }
-        )
+        }
     else:
-        return Config({})
+        config = {}
+    return Config(config)
 
 
 @pytest.fixture
@@ -191,7 +192,7 @@ def jp_configurable_serverapp(
     jp_logging_stream,
     asyncio_loop,
     io_loop,
-    kernel_spec,  # noqa
+    echo_kernel_spec,  # noqa
 ):
     """Starts a Jupyter Server instance based on
     the provided configuration values.
@@ -228,6 +229,9 @@ def _configurable_serverapp(
         c = Config(config)
         c.NotebookNotary.db_file = ":memory:"
 
+        if "default_kernel_name" not in c.MultiKernelManager:
+            c.MultiKernelManager.default_kernel_name = "echo"
+
         default_token = hexlify(os.urandom(4)).decode("ascii")
         if not is_v2:
             kwargs["token"] = default_token

tests/test_jupyter_client.py

@@ -15,6 +15,11 @@ async def test_start_kernel(start_kernel):
     msg = await kc.execute("hello", reply=True)
     assert msg["content"]["status"] == "ok"
 
+    km, kc = await start_kernel("python3")
+    assert km.kernel_name == "python3"
+    msg = await kc.execute("print('hi')", reply=True)
+    assert msg["content"]["status"] == "ok"
+
 
 def test_echo_kernel():
     kernel = EchoKernel()

tests/test_jupyter_server.py

@@ -23,7 +23,7 @@ async def test_send_request(send_request):
 
 async def test_connection(jp_fetch, jp_ws_fetch, jp_http_port, jp_auth_header):
     # Create kernel
-    r = await jp_fetch("api", "kernels", method="POST", body=json.dumps({"name": "echo"}))
+    r = await jp_fetch("api", "kernels", method="POST", body="{}")
     kid = json.loads(r.body.decode())["id"]
 
     # Get kernel info