Add an integration test for relative imports

Summary:
After skimming the implementation of relative imports, it was all tests
that required trusting the test assertions; it's nice to have a test that
actually runs the code.

Reviewed By: alexmalyshev

Differential Revision: D96400606

fbshipit-source-id: f801fe836e05f6f583ed7f673d6a761a1114dd51

Author: stroxler

cinderx/PythonLib/test_cinderx/test_compiler/test_static/decl_visitor.py

@@ -393,3 +393,20 @@ def g(x: C):
         comp = self.compiler(**{"pkg.foo": foo_code, "pkg.mod": mod_code})
         f = self.find_code(comp.compile_module("pkg.mod"), "g")
         self.assertInBytecode(f, "INVOKE_METHOD", ((("pkg.foo", "C"), "f"), 0))
+
+    def test_relative_import_executes_compiled_code(self) -> None:
+        """Relative import should work at runtime when executing compiled module."""
+        foo_code = """
+            class C:
+                def f(self) -> int:
+                    return 42
+        """
+        mod_code = """
+            from .foo import C
+
+            def g() -> int:
+                return C().f()
+        """
+        comp = self.compiler(**{"pkg.foo": foo_code, "pkg.mod": mod_code})
+        with comp.in_module("pkg.mod") as mod:
+            self.assertEqual(mod.g(), 42)