--headless 3x slower than GUI when "numTestsKeptInMemory" set to 0

[Q-back]

Current behavior:

If I'll set "numTestsKeptInMemory": 0 in cypress.json then tests running in GUI (both Chrome and Electron) are 3x faster than in --headless mode. (0:30 vs 1:30)

Desired behavior:

I think speeds should be pretty the same

Steps to reproduce: (app code and test code)

my cypress.json

{
  "pluginsFile": "tests/e2e/plugins/index.js",
  "baseUrl": "http://localhost:8080",
  "viewportWidth": 1100,
  "viewportHeight": 660,
  "video": false,
  "numTestsKeptInMemory": 0
}

my package.json commands

    "test": "vue-cli-service test:e2e --headless --mode=test",
    "test-gui": "vue-cli-service test:e2e --mode=test"

Versions

cypress: 3.4.1
OS: macos 10.14.2

[jennifer-shehane]

Duplicate of #2912, which has never been resolved because a completely reproducible example has never been provided demonstrating this concretely. Please comment in that issue with a complete project that we can run that demonstrates this. We've spent a lot of time trying to reproduce this in the past because performance is really important to us.

Also, there ARE reasons that running in cypress run could be slower than cypress open that are intended behaviors of Cypress as explained here: #2912 (comment)

[Q-back]

I'm really sorry, currently I can't provide an example because I'm working on a closed project. If I'll be able to reproduce the issue outside of it I'll post here for sure. Thanks for fast response 🙂