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Clone

Clone() copies a root scope's service registrations into a new root scope, without carrying over any already-invoked singleton state. It only works on *do.RootScope; regular and virtual scopes cannot be cloned directly.

This is the recommended way to isolate tests: register your services (and mocks) once, then clone the injector for each test case instead of rebuilding it from scratch.

injector := do.New()

Provide[*Car](i, NewCar)
Provide[*Engine](i, NewEngine)

// reset scope
injector = injector.Clone()

Because the clone starts with no invoked services, the next call to do.Invoke re-runs the provider functions and builds fresh instances — nothing is shared with the original injector.

Clone with options​

CloneWithOpts clones a root scope while also overriding its container options, such as the struct tag key used for do.InvokeStruct. Combined with do.Override, it's the standard pattern for swapping a real dependency with a mock in a single test:

injector := do.New()

Provide[*Car](i, NewCar)
Provide[Engine](i, NewEngine)

// clone
injector = injector.CloneWithOpts(&do.InjectorOpts{
    StructTagKey: "di",
})

// replace Engine by *MockEngine
do.Override[Engine](injector, func (i do.Injector) (Engine, error) {
    return &MockEngine{}, nil
})

When to use Clone​

  • Table-driven tests: clone once per test case to avoid state leaking between them.
  • Parallel tests: each goroutine gets its own instances from a shared registration set.
  • Feature flags / A-B setups: clone a base injector and override a handful of services per variant.

Common mistake: cloning the wrong scope​

Clone() and CloneWithOpts() are only available on *do.RootScope. If you're holding a child scope (from injector.Scope("name")) and try to reset it between tests, clone the root scope instead and re-derive the child scope from the clone — cloning a child scope directly isn't supported, since a scope's identity is tied to its position in the parent's tree.

For mocking whole packages instead of individual services, see package loading. For a broader picture of how scopes relate to each other, see Scopes.