matrixConfig

Builds a reusable matrix configuration value to pass to test / testSuite (and their FreeSpec "name"(…) forms), e.g. testSuite("group", matrixConfig { execution = ExecutionMode.Concurrent(4) }) { … }. Unset fields inherit the enclosing matrix scope. testConfig is one of the fields, so this also carries aroundAll / aroundEach / context.

Set concurrency via execution, not testConfig = TestConfig.invocation(...) (matrix derives invocation from execution; a conflicting one is overridden and can break discovery). A testScope(...) (virtual time) applies only to sequential execution — matrix auto-disables it when concurrent — so prefer enabling TestScope on the TestSession, and use aroundEach/aroundAll + withTimeout for timeouts under concurrency.