Cucumber and Minitest with and without Bundler

The simplest code example I could come up with that shows the behaviour I don't understand yet.

Local set up

Program	Version
ruby	3.3.3
bundler	2.5.14
gem	3.5.14

Prepare running the commands

I updated the current version of all the gems my system, including rubygems isteslf and bundler

> gem update --system && gem update && bundle install

Latest version already installed. Done.
Updating installed gems
Nothing to update
Bundle complete! 2 Gemfile dependencies, 17 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.```

Checked the versions:

> gem -v
3.5.14
> bundler -v
Bundler version 2.5.14

With Bundler

 > bundle exec cucumber
Using the default profile...
Feature: Contrived Examples

  Scenario: Add stuff         # features/gives_cucumber_somthing_to_run.feature:3
    Given arguments 40 and 2  # features/step_definitions/general_steps.rb:1
    When they are added       # features/step_definitions/general_steps.rb:6
    Then the sum should be 42 # features/step_definitions/general_steps.rb:10

1 scenario (1 passed)
3 steps (3 passed)
0m0.003s

All is good.

Without Bundler

> cucumber
Using the default profile...
Feature: Contrived Examples

  Scenario: Add stuff         # features/gives_cucumber_somthing_to_run.feature:3
    Given arguments 40 and 2  # features/step_definitions/general_steps.rb:1
    When they are added       # features/step_definitions/general_steps.rb:6
    Then the sum should be 42 # features/step_definitions/general_steps.rb:10
      undefined method `assert_equal' for #<MinitestWorld:0x000000012aac1608> (NoMethodError)
      ./features/step_definitions/general_steps.rb:11:in `"the sum should be {int}"'
      features/gives_cucumber_somthing_to_run.feature:6:in `the sum should be 42'

Failing Scenarios:
cucumber features/gives_cucumber_somthing_to_run.feature:3 # Scenario: Add stuff

1 scenario (1 failed)
3 steps (1 failed, 2 passed)
0m0.050s

I don't understand why I get the NoMethodError in this case.