add unit test for config and integration test with cargo --list

Author: kylematsuda

tests/testsuite/cargo_command.rs

@@ -104,6 +104,32 @@ fn list_command_looks_at_path() {
     );
 }
 
+#[cfg(windows)]
+#[cargo_test]
+fn list_command_looks_at_path_case_mismatch() {
+    let proj = project()
+        .executable(Path::new("path-test").join("cargo-1"), "")
+        .build();
+
+    let mut path = path();
+    path.push(proj.root().join("path-test"));
+    let path = env::join_paths(path.iter()).unwrap();
+
+    // See issue #11814: Environment variable names are case-insensitive on Windows.
+    // We need to check that having "Path" instead of "PATH" is okay.
+    let output = cargo_process("-v --list")
+        .env("Path", &path)
+        .env_remove("PATH")
+        .exec_with_output()
+        .unwrap();
+    let output = str::from_utf8(&output.stdout).unwrap();
+    assert!(
+        output.contains("\n    1                   "),
+        "missing 1: {}",
+        output
+    );
+}
+
 #[cargo_test]
 fn list_command_handles_known_external_commands() {
     let p = project()

tests/testsuite/config.rs

@@ -211,6 +211,31 @@ f1 = 123
     assert_eq!(s, S { f1: Some(456) });
 }
 
+#[cfg(windows)]
+#[cargo_test]
+fn environment_variable_casing() {
+    // Issue #11814: Environment variable names are case-insensitive on Windows.
+    let config = ConfigBuilder::new()
+        .env("Path", "abc")
+        .env("Two-Words", "abc")
+        .env("two_words", "def")
+        .build();
+
+    let var = config.get_env("PATH").unwrap();
+    assert_eq!(var, String::from("abc"));
+
+    let var = config.get_env("path").unwrap();
+    assert_eq!(var, String::from("abc"));
+
+    let var = config.get_env("TWO-WORDS").unwrap();
+    assert_eq!(var, String::from("abc"));
+
+    // Make sure that we can still distinguish between dashes and underscores
+    // in variable names.
+    let var = config.get_env("Two_Words").unwrap();
+    assert_eq!(var, String::from("def"));
+}
+
 #[cargo_test]
 fn config_works_with_extension() {
     write_config_toml(