Add test for environment and environment_pass references

unit_test/options_test.py

@@ -253,3 +253,22 @@ def test_container_engine_option(tmp_path: Path, toml_assignment, result_name, r
 
     assert parsed_container_engine.name == result_name
     assert parsed_container_engine.create_args == result_create_args
+
+
+def test_environment_pass_references():
+    options = Options(
+        platform="linux",
+        command_line_arguments=CommandLineArguments.defaults(),
+        env={
+            "CIBW_ENVIRONMENT_PASS_LINUX": "STARTER MAIN_COURSE",
+            "STARTER": "green eggs",
+            "MAIN_COURSE": "ham",
+            "CIBW_ENVIRONMENT": 'MEAL="$STARTER and $MAIN_COURSE"',
+        },
+    )
+    parsed_environment = options.build_options(identifier=None).environment
+    assert parsed_environment.as_dictionary(prev_environment={}) == {
+        "MEAL": "green eggs and ham",
+        "STARTER": "green eggs",
+        "MAIN_COURSE": "ham",
+    }