Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/google/googletest-rust


https://github.com/google/googletest-rust

Last synced: about 2 months ago
JSON representation

Awesome Lists containing this project

README 

        
# GoogleTest Rust



[![crates.io][crates-badge]][crates-url]

[![docs.rs][docs-badge]][docs-url]

[![Apache licensed][license-badge]][license-url]

[![Build Status][actions-badge]][actions-url]



[crates-badge]: https://img.shields.io/crates/v/googletest.svg

[crates-url]: https://crates.io/crates/googletest

[docs-badge]: https://img.shields.io/badge/docs.rs-googletest-66c2a5

[docs-url]: https://docs.rs/googletest/*/googletest/

[license-badge]: https://img.shields.io/badge/license-Apache-blue.svg

[license-url]: https://github.com/google/googletest-rust/blob/main/LICENSE

[actions-badge]: https://github.com/google/googletest-rust/workflows/CI/badge.svg

[actions-url]: https://github.com/google/googletest-rust/actions?query=workflow%3ACI+branch%3Amain



This library brings the rich assertion types of Google's C++ testing library

[GoogleTest](https://github.com/google/googletest) to Rust. It provides:



 * A framework for writing matchers which can be combined to make a wide range

   of assertions on data,

 * A rich set of matchers providing similar functionality to those included in

   [GoogleTest](https://google.github.io/googletest/reference/matchers.html),

   and

 * A new set of assertion macros offering similar functionality to those of

   [GoogleTest](https://google.github.io/googletest/primer.html#assertions).



**The minimum supported Rust version is 1.66**.



> :warning: The API is not fully stable and may still be changed until we

> publish version 1.0.

>

> Moreover, any items or modules starting with `__` (double underscores) must

> not be used directly. Those items or modules are only for internal uses and

> their API may change without a major version update.



## Learning resources



If you're just getting started with `googletest`, consider going through

the first chapter of

["Advanced testing for Rust applications"](https://github.com/mainmatter/rust-advanced-testing-workshop),

a self-guided Rust course: it provides a guided introduction to the library,

with exercises to help you get comfortable with `googletest` macros,

its matchers and its overall philosophy.



## Assertions and matchers



The core of GoogleTest is its *matchers*. Matchers indicate what aspect of an

actual value one is asserting: (in-)equality, containment, regular expression

matching, and so on.



To make an assertion using a matcher, GoogleTest offers three macros:



 * [`assert_that!`] panics if the assertion fails, aborting the test.

 * [`expect_that!`] logs an assertion failure, marking the test as having

   failed, but allows the test to continue running (called a _non-fatal

   assertion_). It requires the use of the [`gtest`] attribute macro

   on the test itself.

 * [`verify_that!`] has no side effects and evaluates to a [`Result<()>`] whose

   `Err` variant describes the assertion failure, if there is one. In

   combination with the

   [`?` operator](https://doc.rust-lang.org/reference/expressions/operator-expr.html#the-question-mark-operator),

   this can be used to abort the test on assertion failure without panicking. It

   is also the building block for the other two macros above.



For example:



```rust

use googletest::prelude::*;



#[test]

fn fails_and_panics() {

    let value = 2;

    assert_that!(value, eq(4));

}



#[gtest]

fn two_logged_failures() {

    let value = 2;

    expect_that!(value, eq(4)); // Test now failed, but continues executing.

    expect_that!(value, eq(5)); // Second failure is also logged.

}



#[test]

fn fails_immediately_without_panic() -> Result<()> {

    let value = 2;

    verify_that!(value, eq(4))?; // Test fails and aborts.

    verify_that!(value, eq(2))?; // Never executes.

    Ok(())

}



#[test]

fn simple_assertion() -> Result<()> {

    let value = 2;

    verify_that!(value, eq(4)) // One can also just return the last assertion.

}

```



This library includes a rich set of matchers, covering:



 * Equality, numeric inequality, and approximate equality;

 * Strings and regular expressions;

 * Containers and set-theoretic matching.



Matchers are composable:



```rust

use googletest::prelude::*;



#[gtest]

fn contains_at_least_one_item_at_least_3() {

    let value = vec![1, 2, 3];

    expect_that!(value, contains(ge(3)));

}

```



They can also be logically combined:



```rust

use googletest::prelude::*;



#[gtest]

fn strictly_between_9_and_11() {

    let value = 10;

    expect_that!(value, gt(9).and(not(ge(11))));

}

```



## Pattern-matching



One can use the macro [`matches_pattern!`] to create a composite matcher for a

struct or enum that matches fields with other matchers:



```rust

use googletest::prelude::*;



struct AStruct {

    a_field: i32,

    another_field: i32,

    a_third_field: &'static str,

}



#[test]

fn struct_has_expected_values() {

    let value = AStruct {

        a_field: 10,

        another_field: 100,

        a_third_field: "A correct value",

    };

    expect_that!(value, matches_pattern!(AStruct {

        a_field: eq(10),

        another_field: gt(50),

        a_third_field: contains_substring("correct"),

    }));

}

```



## Writing matchers



One can extend the library by writing additional matchers. To do so, create a

struct holding the matcher's data and have it implement the trait [`Matcher`]:



```rust

struct MyEqMatcher {

    expected: T,

}



impl Matcher for MyEqMatcher {

    fn matches(&self, actual: T) -> MatcherResult {

         (self.expected == actual).into()

    }



    fn describe(&self, matcher_result: MatcherResult) -> String {

        match matcher_result {

            MatcherResult::Match => {

                format!("is equal to {:?} the way I define it", self.expected)

            }

            MatcherResult::NoMatch => {

                format!("isn't equal to {:?} the way I define it", self.expected)

            }

        }

    }

}

```



It is recommended to expose a function which constructs the matcher:



```rust

pub fn eq_my_way(expected: T) -> impl Matcher {

    MyEqMatcher { expected }

}

```



The new matcher can then be used in the assertion macros:



```rust

#[gtest]

fn should_be_equal_by_my_definition() {

    expect_that!(10, eq_my_way(10));

}

```



## Non-fatal assertions



Using non-fatal assertions, a single test is able to log multiple assertion

failures. Any single assertion failure causes the test to be considered having

failed, but execution continues until the test completes or otherwise aborts.



This is analogous to the `EXPECT_*` family of macros in GoogleTest.



To make a non-fatal assertion, use the macro [`expect_that!`]. The test must

also be marked with [`gtest`] instead of the Rust-standard `#[test]`.



```rust

use googletest::prelude::*;



#[gtest]

fn three_non_fatal_assertions() {

    let value = 2;

    expect_that!(value, eq(2));  // Passes; test still considered passing.

    expect_that!(value, eq(3));  // Fails; logs failure and marks the test failed.

    expect_that!(value, eq(4));  // A second failure, also logged.

}

```



This can be used in the same tests as `verify_that!`, in which case the test

function must also return [`Result<()>`]:



```rust

use googletest::prelude::*;



#[gtest]

fn failing_non_fatal_assertion() -> Result<()> {

    let value = 2;

    expect_that!(value, eq(3));  // Just marks the test as having failed.

    verify_that!(value, eq(2))?;  // Passes, so does not abort the test.

    Ok(())        // Because of the failing expect_that! call above, the

                  // test fails despite returning Ok(())

}

```



```rust

use googletest::prelude::*;



#[gtest]

fn failing_fatal_assertion_after_non_fatal_assertion() -> Result<()> {

    let value = 2;

    verify_that!(value, eq(3))?; // Fails and aborts the test.

    expect_that!(value, eq(3));  // Never executes, since the test already aborted.

    Ok(())

}

```



### Interoperability



You can use the `#[gtest]` macro together with many other libraries

such as [rstest](https://crates.io/crates/rstest). Just apply both attribute

macros to the test:



```rust

#[gtest]

#[rstest]

#[case(1)]

#[case(2)]

#[case(3)]

fn rstest_works_with_google_test(#[case] value: u32) -> Result<()> {

   verify_that!(value, gt(0))

}

```



Make sure to put `#[gtest]` *before* `#[rstest]`. Otherwise the

annotated test will run twice, since both macros will attempt to register a test

with the Rust test harness.



The macro also works together with

[async tests with Tokio](https://docs.rs/tokio/latest/tokio/attr.gtest.html) in

the same way:



```rust

#[gtest]

#[tokio::test]

async fn should_work_with_tokio() -> Result<()> {

    verify_that!(3, gt(0))

}

```



There is one caveat when running async tests: test failure reporting through

`and_log_failure` will not work properly if the assertion occurs on a different

thread than runs the test.



## Predicate assertions



The macro [`verify_pred!`] provides predicate assertions analogous to

GoogleTest's `EXPECT_PRED` family of macros. Wrap an invocation of a predicate

in a `verify_pred!` invocation to turn that into a test assertion which passes

precisely when the predicate returns `true`:



```rust

fn stuff_is_correct(x: i32, y: i32) -> bool {

    x == y

}



let x = 3;

let y = 4;

verify_pred!(stuff_is_correct(x, y))?;

```



The assertion failure message shows the arguments and the values to which they

evaluate:



```

stuff_is_correct(x, y) was false with

  x = 3,

  y = 4

```



The `verify_pred!` invocation evaluates to a [`Result<()>`] just like

[`verify_that!`]. There is also a macro [`expect_pred!`] to make a non-fatal

predicaticate assertion.



## Unconditionally generating a test failure



The macro [`fail!`] unconditionally evaluates to a `Result` indicating a test

failure. It can be used analogously to [`verify_that!`] and [`verify_pred!`] to

cause a test to fail, with an optional formatted message:



```rust

#[test]

fn always_fails() -> Result<()> {

    fail!("This test must fail with {}", "today")

}

```



## Configuration



This library is configurable through environment variables. Since the

configuration does not impact whether a test fails or not but how a failure is

displayed, we recommend setting those variables in the personal

`~/.cargo/config.toml` instead of in the project-scoped `Cargo.toml`.



### Configuration variable list



| Variable name | Description                                             |

| ------------- | ------------------------------------------------------- |

| NO_COLOR      | Disables colored output. See .   |

| FORCE_COLOR   | Forces colors even when the output is piped to a file.  |



## Contributing Changes



Please read [CONTRIBUTING.md](CONTRIBUTING.md) for details on how to contribute

to this project.



[`and_log_failure()`]: https://docs.rs/googletest/*/googletest/trait.GoogleTestSupport.html#tymethod.and_log_failure

[`assert_that!`]: https://docs.rs/googletest/*/googletest/macro.assert_that.html

[`expect_pred!`]: https://docs.rs/googletest/*/googletest/macro.expect_pred.html

[`expect_that!`]: https://docs.rs/googletest/*/googletest/macro.expect_that.html

[`fail!`]: https://docs.rs/googletest/*/googletest/macro.fail.html

[`gtest`]: https://docs.rs/googletest/*/googletest/attr.gtest.html

[`matches_pattern!`]: https://docs.rs/googletest/*/googletest/macro.matches_pattern.html

[`verify_pred!`]: https://docs.rs/googletest/*/googletest/macro.verify_pred.html

[`verify_that!`]: https://docs.rs/googletest/*/googletest/macro.verify_that.html

[`Describe`]: https://docs.rs/googletest/*/googletest/matcher/trait.Describe.html

[`Matcher`]: https://docs.rs/googletest/*/googletest/matcher/trait.Matcher.html

[`Result<()>`]: https://docs.rs/googletest/*/googletest/type.Result.html