test(devkit): add integration tests for export CSV subcommand

packages/devkit/tests/cli_export.rs

@@ -0,0 +1,42 @@
+use stellar_devkit::cli::export::Export;
+use stellar_devkit::simulation::fee_model::{FeeModel, FeeModelConfig};
+
+#[test]
+fn export_csv_has_correct_header() {
+    let config = FeeModelConfig { seed: Some(1), ..Default::default() };
+    let mut model = FeeModel::new(config);
+    let points = model.generate(5, 0);
+    let csv = Export::to_csv(&points);
+    assert!(
+        csv.starts_with("timestamp,fee,ledger,is_spike\n"),
+        "CSV header mismatch: {csv}"
+    );
+}
+
+#[test]
+fn export_csv_row_count_matches_input() {
+    let config = FeeModelConfig { seed: Some(2), ..Default::default() };
+    let mut model = FeeModel::new(config);
+    let points = model.generate(10, 0);
+    let csv = Export::to_csv(&points);
+    let rows: Vec<&str> = csv.trim().lines().collect();
+    assert_eq!(
+        rows.len(),
+        11,
+        "expected 10 data rows + 1 header, got {}",
+        rows.len() - 1
+    );
+}
+
+#[test]
+fn export_csv_columns_are_parseable() {
+    let config = FeeModelConfig { seed: Some(3), ..Default::default() };
+    let mut model = FeeModel::new(config);
+    let points = model.generate(1, 1_000);
+    let csv = Export::to_csv(&points);
+    let data_line = csv.lines().nth(1).expect("missing data row");
+    let cols: Vec<&str> = data_line.split(',').collect();
+    assert_eq!(cols.len(), 4, "expected 4 columns, got {}", cols.len());
+    assert!(cols[0].parse::<u64>().is_ok(), "timestamp not a u64");
+    assert!(cols[1].parse::<u64>().is_ok(), "fee not a u64");
+}