add: main function

tests/hello_rpg.rs

@@ -0,0 +1,80 @@
+//! Integration tests for the compiler binary against the Hello World program.
+
+use std::process::Command;
+
+/// `CARGO_BIN_EXE_rust-langrpg` is injected by Cargo for integration tests and
+/// always points at the freshly-built binary under `target/`.
+const BIN: &str = env!("CARGO_BIN_EXE_rust-langrpg");
+
+/// Absolute path to hello.rpg, resolved at compile time relative to the crate
+/// root so the test works regardless of the working directory.
+const HELLO_RPG: &str = concat!(env!("CARGO_MANIFEST_DIR"), "/hello.rpg");
+
+// ─────────────────────────────────────────────────────────────────────────────
+// Helper
+// ─────────────────────────────────────────────────────────────────────────────
+
+fn run(args: &[&str]) -> std::process::Output {
+    Command::new(BIN)
+        .args(args)
+        .output()
+        .unwrap_or_else(|e| panic!("failed to spawn '{}': {e}", BIN))
+}
+
+// ─────────────────────────────────────────────────────────────────────────────
+// Tests
+// ─────────────────────────────────────────────────────────────────────────────
+
+/// The compiler should exit 0 when given hello.rpg (no -o flag — tree is
+/// discarded but the parse must still succeed).
+#[test]
+fn hello_rpg_exits_ok() {
+    let out = run(&[HELLO_RPG]);
+    assert!(
+        out.status.success(),
+        "expected exit 0 for hello.rpg\nstderr: {}",
+        String::from_utf8_lossy(&out.stderr),
+    );
+}
+
+/// When -o is supplied the output file must be created and contain a non-empty
+/// parse tree.
+#[test]
+fn hello_rpg_writes_tree() {
+    let out_path = std::env::temp_dir().join("hello_rpg_test_tree.txt");
+
+    let out = run(&["-o", out_path.to_str().unwrap(), HELLO_RPG]);
+
+    assert!(
+        out.status.success(),
+        "compiler failed with -o flag\nstderr: {}",
+        String::from_utf8_lossy(&out.stderr),
+    );
+
+    let tree = std::fs::read_to_string(&out_path)
+        .unwrap_or_else(|e| panic!("could not read output file '{}': {e}", out_path.display()));
+
+    assert!(
+        !tree.trim().is_empty(),
+        "output file is empty — expected a parse tree",
+    );
+
+    // The tree should reference at least the top-level <program> non-terminal.
+    assert!(
+        tree.contains("program"),
+        "parse tree does not mention <program>:\n{tree}",
+    );
+}
+
+/// The compiler must print the file name to stderr as "ok: hello.rpg" (or the
+/// full path) when the parse succeeds.
+#[test]
+fn hello_rpg_reports_ok_on_stderr() {
+    let out = run(&[HELLO_RPG]);
+
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert!(
+        stderr.starts_with("ok:"),
+        "expected stderr to start with 'ok:'\ngot: {stderr}",
+    );
+}