test: add integration test for CSV reference resolution

Add integration tests for `parseCsv` using fixture CSV files
to verify that table references are correctly resolved across
multiple files.

src/csv-loader/fixtures/order_rev.csv

@@ -0,0 +1,3 @@
+id,user,total
+string,string,int
+o01,u01,100

src/csv-loader/fixtures/user_rev.csv

@@ -0,0 +1,5 @@
+# orders := ~order_rev(user)
+id,name
+string,string
+u01,Alice
+u02,Bob

src/csv-loader/integration.test.ts

@@ -0,0 +1,31 @@
+import { describe, it, expect } from "vitest";
+import { parseCsv } from "./loader";
+import * as path from "path";
+import * as fs from "fs";
+
+const fixturesDir = path.join(__dirname, "fixtures");
+
+describe("parseCsv - integration: loading two CSV tables from fixtures", () => {
+  it("should load user_rev and order_rev tables and resolve orders array with correct length", () => {
+    const userCsv = fs.readFileSync(
+      path.join(fixturesDir, "user_rev.csv"),
+      "utf-8",
+    );
+
+    const result = parseCsv(userCsv, {
+      emitTypes: false,
+      currentFilePath: path.join(fixturesDir, "user_rev.csv"),
+    });
+
+    expect(result.data).toHaveLength(2);
+
+    // Alice (u01) should have 1 order
+    const aliceOrders = result.data[0].orders as Record<string, unknown>[];
+    expect(aliceOrders).toHaveLength(1);
+    expect(aliceOrders[0].id).toBe("o01");
+
+    // Bob (u02) should have 0 orders
+    const bobOrders = result.data[1].orders as Record<string, unknown>[];
+    expect(bobOrders).toHaveLength(0);
+  });
+});