Add Servo sidecar snapshot command

crates/ely_servo_host/tests/sidecar.rs

@@ -0,0 +1,56 @@
+#![cfg(feature = "servo-engine")]
+
+use std::{error::Error, process::Command};
+
+const WIDTH: u64 = 640;
+const HEIGHT: u64 = 480;
+
+#[test]
+fn sidecar_snapshots_prd_site_to_rgba_file() -> Result<(), Box<dyn Error>> {
+    let output_path =
+        std::env::temp_dir().join(format!("ely-servo-sidecar-{}-example.rgba", std::process::id()));
+    if output_path.exists() {
+        std::fs::remove_file(&output_path)?;
+    }
+
+    let output = Command::new(env!("CARGO_BIN_EXE_ely_servo_sidecar"))
+        .arg("snapshot")
+        .arg("--url")
+        .arg("https://example.com")
+        .arg("--rgba-out")
+        .arg(&output_path)
+        .arg("--width")
+        .arg(WIDTH.to_string())
+        .arg("--height")
+        .arg(HEIGHT.to_string())
+        .output()?;
+
+    assert!(
+        output.status.success(),
+        "status: {:?}\nstdout: {}\nstderr: {}",
+        output.status.code(),
+        String::from_utf8_lossy(&output.stdout),
+        String::from_utf8_lossy(&output.stderr)
+    );
+
+    let report: serde_json::Value = serde_json::from_slice(&output.stdout)?;
+    assert_eq!(report_field_as_u64(&report, "width")?, WIDTH);
+    assert_eq!(report_field_as_u64(&report, "height")?, HEIGHT);
+    assert_eq!(report_field_as_u64(&report, "rgba_byte_count")?, WIDTH * HEIGHT * 4);
+    assert!(report_field_as_u64(&report, "non_white_pixel_count")? > 0);
+    assert!(report_field_as_u64(&report, "sample_hash")? > 0);
+    assert_eq!(std::fs::metadata(&output_path)?.len(), WIDTH * HEIGHT * 4);
+
+    std::fs::remove_file(&output_path)?;
+    Ok(())
+}
+
+fn report_field_as_u64(
+    report: &serde_json::Value,
+    field: &'static str,
+) -> Result<u64, Box<dyn Error>> {
+    report
+        .get(field)
+        .and_then(serde_json::Value::as_u64)
+        .ok_or_else(|| format!("missing numeric report field: {field}").into())
+}