let Rpc client take a deltachat-rpc-server path and write a test using it

deltachat-rpc-client/src/deltachat_rpc_client/rpc.py

@@ -54,7 +54,7 @@ class RpcMethod:
 class Rpc:
     """RPC client."""
 
-    def __init__(self, accounts_dir: Optional[str] = None, **kwargs):
+    def __init__(self, accounts_dir: Optional[str] = None, rpc_server_path="deltachat-rpc-server", **kwargs):
         """Initialize RPC client.
 
         The given arguments will be passed to subprocess.Popen().
@@ -66,6 +66,7 @@ class Rpc:
             }
 
         self._kwargs = kwargs
+        self.rpc_server_path = rpc_server_path
         self.process: subprocess.Popen
         self.id_iterator: Iterator[int]
         self.event_queues: dict[int, Queue]
@@ -88,7 +89,7 @@ class Rpc:
             popen_kwargs["preexec_fn"] = os.setpgrp  # noqa: PLW1509
 
         popen_kwargs.update(self._kwargs)
-        self.process = subprocess.Popen("deltachat-rpc-server", **popen_kwargs)
+        self.process = subprocess.Popen(self.rpc_server_path, **popen_kwargs)
         self.id_iterator = itertools.count(start=1)
         self.event_queues = {}
         self.request_results = {}

deltachat-rpc-client/tests/test_rpc_virtual.py

@@ -0,0 +1,16 @@
+import subprocess
+import sys
+
+from deltachat_rpc_client import DeltaChat, Rpc
+
+
+def test_install_venv_and_use_other_core(tmp_path):
+    venv = tmp_path.joinpath("venv1")
+    python = sys.executable
+    subprocess.check_call([python, "-m", "venv", venv])
+    subprocess.check_call([venv / "bin" / "pip", "install", "deltachat-rpc-server==2.20.0"])
+    rpc = Rpc(accounts_dir=tmp_path.joinpath("accounts"), rpc_server_path=venv.joinpath("bin", "deltachat-rpc-server"))
+
+    with rpc:
+        dc = DeltaChat(rpc)
+        assert dc.rpc.get_system_info()["deltachat_core_version"] == "v2.20.0"