Best approach for mocking struct methods with different behavior in tests

[Sze]

You also could use build options to pass in the value and make it changeable from the outside.

Passing build option to code from the zig command line?

In build.zig: const use_native_c_inner_loops = b.option(bool, "loops", "use native C inner loops") orelse false; const options = b.addOptions(); options.addOption(bool, "use_native_c_inner_loops", use_native_c_inner_loops); exe.addOptions("config", options); Then in your code const config = @import("config"); if (config.use_native_c_inner_loops) ... This means that you can do zig build run -Dloops to enagle the feature.

Alternatively you could import a module @import("settings") and then use the build system to switch between two different implementations for that module, or even generate one of them (build options are one way to generate a module of imported options).

This is related:

Modules are isomorphic to generic functions

You can get most of this same behavior even without introducing new concepts. Have your types be parametrized in a non-generic way with type parameters that come from other Zig modules, and then use the Zig build system to implement “generics” when composing an output executable (or a test one, or whatever artifact you’re generating). In concrete (but a bit pseudozig) terms: // Replica.zig const StateMachine = @import("StateMachine"); const Storage = @import("Storage"); state: StateMachine, …