TypeScriptBrowserPetstoreClientTests failure in CircleCI node 3

CircleCI tests (node 3) failed more often these days:

Running tests...

Running 2 test files...


dist/isomorphic-fetch.test.js:

 ❌ Isomorphic Fetch > GET-Request
      Error: Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.
        at createTimeoutError (node_modules/@web/test-runner-mocha/dist/autorun.js:1:243195)
        at Ty.Gg._timeoutError (node_modules/@web/test-runner-mocha/dist/autorun.js:1:259145)
        at node_modules/@web/test-runner-mocha/dist/autorun.js:1:257217

 ❌ Isomorphic Fetch > POST-Request
      Error: Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.
        at createTimeoutError (node_modules/@web/test-runner-mocha/dist/autorun.js:1:243195)
        at Ty.Gg._timeoutError (node_modules/@web/test-runner-mocha/dist/autorun.js:1:259145)
        at node_modules/@web/test-runner-mocha/dist/autorun.js:1:257217

Chromium: |██████████████████████████████| 2/2 test files | 10 passed, 2 failed

Finished running tests in 5s with 2 failed tests.


[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:exec (npm-test) on project TypeScriptBrowserPetstoreClientTests: Command execution failed.: Process exited with an error: 1 (Exit value: 1) -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

e.g. https://app.circleci.com/pipelines/github/OpenAPITools/openapi-generator/23117/workflows/8a4b3cbe-5ab0-4f3f-8351-f40621cd7e82/jobs/65428

maybe httpbin.org is throttling connections from the CI? not sure but we should switch to Echo API server instead: https://github.com/OpenAPITools/openapi-generator/wiki/Integration-Tests#echo-server

cc @TiFu (2017/07) @taxpon (2017/07) @sebastianhaas (2017/07) @kenisteward (2017/07) @Vrolijkx (2017/09) @macjohnny (2018/01) @topce (2018/10) @akehir (2019/07) @petejohansonxo (2019/11) @amakhrov (2020/02) @davidgamero (2022/03) @mkusaka (2022/04)

also cc @TiFu - the author of the typescript client generator

Start with the failing dist/isomorphic-fetch.test.js GET-Request and POST-Request tests and compare their HTTP target with the Echo server instructions in the linked OpenAPI Generator wiki. Confirm the failure is addressed by using the Echo API server, then rerun the TypeScriptBrowserPetstoreClientTests CircleCI test command and verify both requests pass.