Highly interactive development environments (HIDEs) enable uninterrupted development flow through continuous program evolution and rapid hypothesis checking. However, traditional testing approaches -- typically executed separately via CLI -- isolate tests from HIDE tooling (interactive debuggers, value and stack inspectors, etc.) and introduce disruptive delays due to coarse execution granularity and lack of runtime context. This disconnect breaks development flow by exceeding critical attention thresholds. In this paper we present a library that provides runtime representation for tests, allowing tight integration with HIDEs, and enabling immediate access to HIDE tooling in the context of test failure. We then describe development workflows enhanced with testing and demonstrate how they achieve subsecond test reexecution times crucial for maintaining developer focus.