Preserving original prototype method behavior versus partial mock generation in Jasmine 4 migration

Investigate the this-binding behavior of Jasmine spyOn when applied to prototype methods in Jasmine 4, particularly how the configuration interacts with and.callThrough(). The goal is to determine whether prototype method invocation via an instance reliably receives the correct context, or whether intermittent failures correlate with spy configuration choices.

Documented behavior indicates that Jasmine 2.x spyOn replaces the original method by default, while Jasmine 3+ requires and.callThrough() to preserve the implementation. However, the research brief flags an unresolved decision regarding prototype method this-binding in Jasmine 4, where failures appear dependent on and.callThrough() settings. Additionally, createSpyObj in earlier versions throws on non-enumerable properties, limiting its usefulness for class-based mocks, though Jasmine 4 can generate partial mocks from object literals.

The concrete constraint involves migrating existing test suites across major Jasmine versions while maintaining predictable method behavior and correct this-context for prototype-dependent code. The uncertainty centers on whether and.callThrough() mitigates the reported intermittent binding issues or whether the problem persists across configuration variants.

• Does spyOn(obj.prototype.method) in Jasmine 4 bind the instance context correctly when and.callThrough() is omitted?
• Does adding and.callThrough() to a spyOn of a prototype method stabilize this-binding, or does it introduce other side effects?
• Can createSpyObj('MyClass', ['method']) reliably mock prototype methods without triggering non-enumerable property errors in Jasmine 4?