add k6 benchmark script

bench.js

@@ -0,0 +1,52 @@
+import http from "k6/http";
+import { check } from "k6";
+import { SharedArray } from "k6/data";
+
+export const options = {
+  discardResponseBodies: true,
+  scenarios: {
+    sequential_test: {
+      executor: "per-vu-iterations",
+      vus: 1,
+      iterations: 1,
+      maxDuration: "30m",
+    },
+  },
+};
+
+const testData = new SharedArray("test requests", function () {
+  return JSON.parse(open("answer.json")).tests;
+});
+
+export default function () {
+  console.log(`Starting sequential test run with ${testData.length} requests.`);
+
+  for (const testCase of testData) {
+    const requestBody = testCase.request;
+    const testName = testCase.name;
+
+    const url = "http://localhost:7007/api/image/generate";
+    const payload = JSON.stringify(requestBody);
+    const params = {
+      headers: {
+        "Content-Type": "application/json",
+        Accept: "image/png",
+      },
+      tags: {
+        name: testName,
+      },
+      timeout: "200s",
+    };
+
+    console.log(`'${testName}'`);
+    const res = http.post(url, payload, params);
+    console.log(`'${testName}' duration=${res.timings.duration}ms`);
+    check(res, {
+      "status is 200 (OK)": (r) => r.status === 200,
+      "content-type is image/png": (r) =>
+        r.headers["Content-Type"] === "image/png",
+    });
+  }
+
+  console.log("Sequential test run finished.");
+}