Attribute Macro faux::create

#[create]

Transforms a struct into a mockable version of itself.

An associated function called faux is created for the tagged struct, masking the original definition of the struct by changing its name.

Use cargo-expand to see the changes to your struct after macro expansion.

Requirements

This macro deliberately fails to compile if any of the struct’s fields are not private. Otherwise, a user of the struct could try to access the field directly when it no longer exists in the transformed version.

Only methods within impl blocks tagged by #[methods] may use the struct’s fields.

Examples

#[cfg_attr(test, faux::create)]
pub struct MyStruct {
    a: i32,
    b: Vec<u32>,
}

#[cfg_attr(test, faux::methods)]
impl MyStruct {
    /* methods go here */
}

// creates a mock instance of MyStruct
let my_mock = MyStruct::faux();

Attribute arguments

self_type

Customizes storage of real instances of the mockable struct.

If self_type is set, it must be set to the same value in all #[methods] for this struct.

Explanation

By default, #[faux::create] transform a struct from:

#[faux::create]
struct MyStruct { /* fields */ }

into something like:

struct MyStruct(MaybeFaux);

enum MaybeFaux {
  // when a mock is created we use this variant
  Mock(/* snip */),
  // when a real instance is created we use this variant
  // stores an owned instance of the struct
  // not a smart pointer to the struct
  Real(OriginalMyStruct),
}

// the definition of the original struct
struct OriginalMyStruct { /* fields */ }

This works well when constructors of MyStruct returns an owned instance. There are some cases, however, where the constructor returns a smart pointer (i.e., Rc<Self>). To support such cases, use this attribute argument to customize how faux will wrap the real instance of your struct.

Examples

use std::sync::Arc;

#[faux::create(self_type = "Arc")]
pub struct MyStruct {
    /* private fields */
}

#[faux::methods(self_type = "Arc")]
impl MyStruct {
    pub fn new() -> Arc<Self> {
        /* implementation */
    }

    /* more methods */
}

Allowed values:

• #[create(self_type = "Owned")] (default)
• #[create(self_type = "Rc")]
• #[create(self_type = "Arc")]
• #[create(self_type = "Box")]