Create tests for rush files with cycled dependencies

tests/cycled.rs

@@ -0,0 +1,87 @@
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+use std::process::{Command, Output};
+
+const MANIFEST_PATH: &str = env!("CARGO_MANIFEST_DIR");
+
+#[inline]
+fn create_rush_file(name: &str, content: &str) {
+    let mut path_buf = PathBuf::from(name);
+    _ = path_buf.set_extension("rush");
+
+    let path = path_buf.display();
+
+    let mut file = match File::create(&path_buf) {
+        Ok(ok) => ok,
+        Err(e) => panic!("could not create {path}: {e}")
+    };
+
+    if let Err(e) = file.write_all(content.as_bytes()) {
+        panic!("could not write to {path}: {e}")
+    }
+}
+
+#[inline]
+fn run_rush(path: &str) -> Output {
+    let binary_path = format!("{MANIFEST_PATH}/target/debug/rush");
+    Command::new(binary_path)
+        .arg(format!("-f {path}.rush"))
+        .output()
+        .expect("could not execute command")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn cycled() {
+        let file_path = "cycled";
+
+        create_rush_file(file_path, r#"rule echo
+  command = echo "hello $in"
+
+build hello: echo hello
+build all: hello"#);
+
+        let out = run_rush(file_path);
+
+        assert!(!out.status.success());
+
+        let stderr = unsafe {
+            std::str::from_utf8_unchecked(&out.stderr)
+        };
+
+        assert!{
+            stderr.contains(r#"cycled.rush:4: edge "hello" depends on itself"#)
+        }
+    }
+
+    #[test]
+    fn cycled_path() {
+        let file_path = "cycled_path";
+
+        create_rush_file(file_path, r#"rule echo
+  command = echo "Building $out"
+
+build A: echo B
+build B: echo C
+build C: echo A
+
+default A"#);
+
+        let out = run_rush(file_path);
+
+        assert!(!out.status.success());
+
+        let stderr = unsafe {
+            std::str::from_utf8_unchecked(&out.stderr)
+        };
+
+        assert!{
+            stderr.contains(r#"cycled_path.rush:4: cycle detected: A -> B -> C -> A
+note: edge "A" is causing the cycle"#)
+        }
+    }
+}