factor out mock python repl (#43)

tests/unit_tests/test_python.py

@@ -0,0 +1,34 @@
+"""Test functionality of Python REPL."""
+
+import pytest
+
+from langchain.python import PythonREPL
+
+
+def test_python_repl() -> None:
+    """Test functionality when globals/locals are not provided."""
+    repl = PythonREPL()
+
+    # Run a simple initial command.
+    repl.run("foo = 1")
+    assert repl._locals["foo"] == 1
+
+    # Now run a command that accesses `foo` to make sure it still has it.
+    repl.run("bar = foo * 2")
+    assert repl._locals["bar"] == 2
+
+
+def test_python_repl_no_previous_variables() -> None:
+    """Test that it does not have access to variables created outside the scope."""
+    foo = 3  # noqa: F841
+    repl = PythonREPL()
+    with pytest.raises(NameError):
+        repl.run("print(foo)")
+
+
+def test_python_repl_pass_in_locals() -> None:
+    """Test functionality when passing in locals."""
+    _locals = {"foo": 4}
+    repl = PythonREPL(_locals=_locals)
+    repl.run("bar = foo * 2")
+    assert repl._locals["bar"] == 8