wp-browser: [BUG] Running tests in a separate process and with preservedGlobalState fails

Environment OS: MacOS PHP version: 7.3 Installed Codeception version: 4.1.5 Installed wp-browser version: 2.5.5 WordPress version: 5.4.1 Local development environment: VVV WordPress structure and management: default

Can you perform the test manually?

Testing REST response through Insomnia works.

Codeception configuration file
Paste, in a fenced YAML block, the content of your Codeception configuration file; remove any sensitive data!

paths:
    tests: tests
    output: tests/_output
    data: tests/_data
    support: tests/_support
    envs: tests/_envs
actor_suffix: Tester
extensions:
    enabled:
        - Codeception\Extension\RunFailed
    commands:
        - Codeception\Command\GenerateWPUnit
        - Codeception\Command\GenerateWPRestApi
        - Codeception\Command\GenerateWPRestController
        - Codeception\Command\GenerateWPRestPostTypeController
        - Codeception\Command\GenerateWPAjax
        - Codeception\Command\GenerateWPCanonical
        - Codeception\Command\GenerateWPXMLRPC
params:
    - .env.testing
coverage:
    enabled: true
    include:
        - src/*
    exclude:
        - src/Core/CompiledContainer.php
    low_limit: 30
    high_limit: 75
settings:
    colors: true
    memory_limit: 1024M

Suite configuration file Paste, in a fenced YAML block, the content of the suite configuration file; remove any sensitive data!

# Codeception Test Suite Configuration
#
# Suite for unit or integration tests that require WordPress functions and classes.

actor: IntegrationTester
modules:
    enabled:
        - WPLoader
        - \Helper\Integration
    config:
        WPLoader:
            wpRootFolder: "%WP_ROOT_FOLDER%"
            dbName: "%TEST_DB_NAME%"
            dbHost: "%TEST_DB_HOST%"
            dbUser: "%TEST_DB_USER%"
            dbPassword: "%TEST_DB_PASSWORD%"
            tablePrefix: "%TEST_TABLE_PREFIX%"
            domain: "%TEST_SITE_WP_DOMAIN%"
            adminEmail: "%TEST_SITE_ADMIN_EMAIL%"
            title: "Test"
            plugins: ['advanced-custom-fields-pro/acf.php', 'classic-editor/classic-editor.php', 'members/members.php', 'my-plugin/my-plugin.php']
            activatePlugins: ['advanced-custom-fields-pro/acf.php', 'classic-editor/classic-editor.php', 'members/members.php', 'my-plugin/my-plugin.php']

Describe the bug When running a test that has a

  /**
   * Test successful login request
   *
   * @runInSeparateProcess
   * @preserveGlobalState disabled
   */

I get this error:

1) LoginEndpointTest: Request was successful
 Test  tests/Integration/Endpoints/LoginEndpointTest.php:testRequestWasSuccessful

  [PHPUnit\Framework\Exception] PHP Fatal error:  Uncaught Error: Class 'Codeception\TestCase\WPTestCase' not found in /Users/denis.zoljom/vagrant-local/www/infinum/my-project/public_html/wp-content/plugins/my-plugin/tests/Integration/Endpoints/LoginEndpointTest.php:16
Stack trace:
#0 Standard input code(31): require_once()
#1 Standard input code(111): __phpunit_run_isolated_test()
#2 {main}
  thrown in /Users/denis.zoljom/vagrant-local/www/infinum/my-project/public_html/wp-content/plugins/my-plugin/tests/Integration/Endpoints/LoginEndpointTest.php on line 16
Fatal error: Uncaught Error: Class 'Codeception\TestCase\WPTestCase' not found in /Users/denis.zoljom/vagrant-local/www/infinum/my-project/public_html/wp-content/plugins/my-plugin/tests/Integration/Endpoints/LoginEndpointTest.php:16
Stack trace:
#0 Standard input code(31): require_once()
#1 Standard input code(111): __phpunit_run_isolated_test()
#2 {main}
  thrown in /Users/denis.zoljom/vagrant-local/www/infinum/my-project/public_html/wp-content/plugins/my-plugin/tests/Integration/Endpoints/LoginEndpointTest.php on line 16

To Reproduce

Add the docblocks with annotations before running tests.

Expected behavior

The test should be able to run in a separate process.