How do I import submodules in another submodule which are part of the tests/ directory?

Question

My goal is to write a test-module(tests/) to an existing rust package.

my package directory tree looks similar to below example_package

example_package
|
├── Cargo.toml
├── src
│   ├── lib.rs
|   ├── other_module.rs
│   ├── main.rs
└── tests
    ├── lib.rs
    ├── test1.rs
    └── test_fixtures
        ├── mod.rs
        ├── test_fixture1.rs
        └── test_fixture2.rs

Here

• test-fixtures/ - is the directory which has common test inputs used in actual testcases.
• test1.rs - is the actual testcase which imports test-fixtures/ and tests a testcase.

But when I tried to import fixtures in test1.rs as below

//tried all below three different ways
use crate::test_fixtures;
//use self::test_fixtures;
//use super::test_fixtures;

The code fails at compile time.

 --> tests/test1.rs:2:5
  |
2 | use crate::test_fixtures;
  |     ^^^^^^^^^^^^^^^^^^^^ no `test_fixtures` in the root

What is the right way to import a submodule in another submodule which are part of tests/?

Code:

// tests$ cat lib.rs 
pub mod test_fixtures;
pub mod test1;

// tests$ cat test_fixtures/mod.rs 
pub mod test_fixture1;
pub mod test_fixture2;

// tests$ cat test_fixtures/test_fixture1.rs 
pub fn test_fixture1() {
    
    print!("test_fixture1");
}

// tests$ cat test_fixtures/test_fixture2.rs 
pub fn test_fixture2() {
    
    print!("test_fixture2");
}

// tests$ cat test1.rs 
use crate::test_fixtures;
//use self::test_fixtures;
//use super::test_fixtures;
pub fn test1() {
    println!("running test1");
    
}

Answer 1

This is documented in the book, section Test Organisation, subsection Submodules in Integration Tests:

As mentioned earlier, each file in the tests directory is compiled as its own separate crate.

[...]

After we’ve created tests/common/mod.rs, we can use it from any of the integration test files as a module. Here’s an example of calling the setup function from the it_adds_two test in tests/integration_test.rs:

use adder;

mod common;

#[test]
fn it_adds_two() {
    common::setup();
    assert_eq!(4, adder::add_two(2));
}

Note that the mod common; declaration is the same as the module declaration we demonstrated in Listing 7-21. Then in the test function, we can call the common::setup() function.

Answer 2

└── tests
    ├── lib.rs
    ├── test1.rs
    └── test_fixtures
        ├── mod.rs
        ├── test_fixture1.rs
        └── test_fixture2.rs

The file structure presented makes an incorrect assumption. The tests folder is not a library crate. Adding a file named lib.rs inside the tests folder will not declare modules for use on all integration tests.

Instead, declare the common modules (such as test_fixtures) in each integration test file, or create a helper library which is shared by all of them.

See also:

• What is an idiomatic way to have shared utility functions for integration tests and benchmarks?
• Cannot import a module in an integration test

Answer 3

Your tests/test1.rs file should look like this,

mod test_fixtures;

#[test]
fn test1() {
    test_fixtures::test_fixture2
}

Notice, that you need to use mod to use the local module.

This tells the rust compiler to include a file named test_fixtures.rs or alternatively look for test_fixtures folder with mod.rs file in it.