Rust differentiates between “unit” exams and “integration” exams. I added double quotes as a result of I consider the semantics could be deceptive. Right here’s what they imply:
- Unit exams are written in the identical file as the primary. You annotate them with the
#[test]macro and namecargo take a look atas seen above - Integration exams are exterior to the code to check. You annotate code to be a part of integration exams with the
#[cfg(test)]macro.
Evaluates boolean mixtures of configuration flags at compile-time.
Along with the
#[cfg]attribute, this macro is supplied to permit boolean expression analysis of configuration flags. This steadily results in much less duplicated code.
The cfg macro affords numerous out-of-the-box configuration variables:
| Variable | Description | Instance |
|---|---|---|
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Goal’s CPU structure |
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Platform characteristic out there for the present compilation goal |
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Goal’s working system |
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Extra generic description of a goal, such because the household of the working programs or architectures that the goal typically falls into |
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Additional disambiguating details about the goal platform with details about the |
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Goal’s pointer width in bits |
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Vendor of the goal |
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Enabled when compiling the take a look at harness |
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When the crate compiled is being compiled with the |
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Relying on the panic technique |
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You might have seen the take a look at flag among the many many variables. To put in writing an integration take a look at, annotate the code with the #[cfg(test)] macro:
#[cfg(test)]
fn test_something() {
// No matter
}One also can use the macro to offer various code within the take a look at context:
fn howdy() -> &'static str {
return "Hey world";
}
#[cfg(test)]
fn howdy() -> &'static str {
return "Hey take a look at";
}The above snippet works throughout cargo run however not throughout cargo take a look at. Within the first case, the second operate is ignored; within the second, it’s not, and Rust tries to compile two features with the identical signature.
error[E0428]: the title `howdy` is outlined a number of occasions
--> src/lib.rs:10:1
|
5 | fn howdy() -> &'static str {
| -------------------------- earlier definition of the worth `howdy` right here
...
10 | fn howdy() -> &'static str {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ `howdy` redefined right here
|
= observe: `howdy` have to be outlined solely as soon as within the worth namespace of this module
Luckily, the cfg macro affords boolean logic. Therefore we will negate the take a look at config for the primary operate:
fn fundamental() {
println!("{}", howdy());
}
#[cfg(not(test))]
fn howdy() -> &'static str {
return "Hey world";
}
#[cfg(test)]
fn howdy() -> &'static str {
return "Hey take a look at";
}
#[test]
fn test_hello() {
assert_eq!(howdy(), "Hey take a look at");
}cargo runyieldsHey worldcargo take a look atcompiles then executes the take a look at efficiently
Whereas it solves our downside, it has apparent flaws:
- It’s binary – take a look at context or not
- It doesn’t scale: after a selected measurement, the sheer variety of annotations will make the venture unmanageable
