update readme, include content-type headers in requests

README.md

@@ -1,11 +1,24 @@
 # k6-script-from-har
 
 Dead simple k6 test generator.  
-Given a har file, this script scrapes and generates idiomatic k6 test code.  
+Given a har file, this script parses and generates cleanly factored k6 test code.  
+[Only `fetch` calls]  
 
-Create a .har file by opening a browser's network tab, navigate, click `export HAR` button. Or can be combined with tools like `Playwright` to have automated tests generate the .har file.  
+This is an alternative to the [har-to-k6](https://k6.io/docs/test-authoring/create-tests-from-recordings/using-the-har-converter/
+) converter which in our experience created messy generated "write only" code that required a lot of clean up every time we used it.
 
-Includes `testTemplate.js` and `testCommon.js` as a starting factoring of shared structure. May be modified after install to your liking. Includes example for getting Auth bearer tokens and attaching them to requests.
+## Who this is for
+We use this for **workflow** load testing of a backend heavy SPA with 10s or 100s of users.
+
+We wanted to measure
+1. Realistic load characteristics (real-world usage conditions)
+2. Workflow completion time
+    * baseline time for one virtual user
+    * how far can we push virtual user count until the time is unacceptable (e.g. 20s for a multi-page workflow)
+3. Infrastructure reliability
+    * at how many virtual users does something in the infrastructure break (follow up - what broke, how do we harden our infra)
+
+The record and playback approach was a good fit for us. We also wanted basic checks in place e.g. failure response status should show up red instead of green in results.
 
 ## Installation
 Ensure k6 is [installed](https://grafana.com/docs/k6/latest/set-up/install-k6/)
@@ -75,3 +88,29 @@ The included testCommon.js and testTemplate.js files include helpers and reasona
         * without these checks the performance tests could appear to succeed even though individual calls were beginning to fail, or take a long time.
     * Review the contents of testCommon.js for more details
 
+## Example code output
+
+```ts
+import { httpRequest, commonSetup, state } from '/testCommon.js';
+
+const given_vus = __ENV.AT_VU_COUNT === undefined ? 15 : __ENV.AT_VU_COUNT;
+const given_iterations = __ENV.AT_ITERATIONS === undefined ? given_vus * 3 : __ENV.AT_ITERATIONS;
+
+export const options = {
+	vus: given_vus,
+	iterations: given_iterations,
+};
+
+export function setup() {
+	commonSetup();
+	return state;
+}
+
+export default function (setup_state) {
+	Object.assign(state, setup_state);
+	httpRequest('GET', 'https://status.k6.io/api/v2/status.json');
+	httpRequest('GET', 'https://k6.io/data/jobs-positions.json');
+}
+
+
+```

bin/k6scriptfromhar.js

@@ -21,7 +21,7 @@ var allRequests = har.log.entries
 .filter(e => e._resourceType === 'fetch')
 .map(e => e.request);
 
-const k6TestCodeLines = allRequests.map(r => `httpRequest('${r.method}','${r.url}'${r.postData ? ', ' + JSON.stringify(JSON.parse(r.postData.text)) : ''});`);
+const k6TestCodeLines = allRequests.map(r => `httpRequest('${r.method}', '${r.url}'${(!r.postData ? '' : `, ${JSON.stringify(r.postData.text)}, { headers: {'Content-Type': '${r.postData.mimeType}'} }`)});`);
 const testBody = k6TestCodeLines.join('\n\t');
 
 var testTemplate = fsSync.readFileSync("./testTemplate.js", {encoding: 'utf8'});

src/testCommon.js

@@ -3,20 +3,26 @@ import { check } from 'k6';
 
 export const state = {};
 export function httpRequest(method, url, body, params = {}) {
+    //attach Authorization header if access_token is set
     if (state.access_token) params.headers = Object.assign({ "Authorization": 'Bearer ' + state.access_token }, params.headers ? params.headers : {});
+
+    //default to JSON content type for POST requests
     if (method === 'POST')
-        params.headers = Object.assign({ "Content-Type": "application/json-patch+json", "Accept": "*/*" }, params.headers ? params.headers : {});
         params.timeout = (params.timeout !== undefined ? params.timeout : 600000); //default to 10m timeout instead of 60s implicit default
 
     const res = http.request(method, url, JSON.stringify(body), params);
 
-    if (!(res.status >= 200 && res.status < 400)) {
+    const isSuccessCode = (res.status >= 200 && res.status < 400);
+    if (!isSuccessCode) {
+        //log to enable troubleshooting after the test run
         const fileAndLineNumber = new Error().stack.split('\n')[2];
         console.log('\n\n' + fileAndLineNumber + ' ' + res.url);
         console.log({ res });
     }
+
+    //some reasonable default checks, feel free to modify
     const checks = {};
-    checks[url + ' status 200-399'] = r => r.status >= 200 && r.status < 400;
+    checks[url + ' status ' + res.status] = r => isSuccessCode;
     checks[url + ' timing < 10s'] = r => r.timings.duration < 10000;
     check(res, checks);
 }