4.3 KiB
Getting Started
These exercises lean on Test-Driven Development (TDD), but they're not an exact match.
The following steps assume that you are in the same directory as the exercise.
You must have rust installed. Follow the Installing Rust chapter in the Rust book. The getting started with rust section from exercism is also useful.
Step 1
Run the test suite. It can be run with cargo, which is installed with rust.
$ cargo test
This will fail, complaining that hello-world could not compile.
To fix this, create a new directory called src.
Create a new file called, lib.rs, inside the src directory.
Step 2
Run the test again. It will give you a new error, another compile error.
Our lib.rs does not contain any code, specifically the hello()
function that our test is looking for.
Fixing the Error
To fix it, open up the src/lib.rs file and add the following code:
pub fn hello(name: Option<&str>) -> String {
"".to_string()
}
Our test is looking for the hello() function from the hello_world
crate. lib.rs, by default, is our crate root and our test
is looking for the hello() function there.
The code we are adding to lib.rs defines a public function (pub fn) that is called "hello".
The function accepts a name as an optional argument (Option).
The function returns a String.
We start by returning an empty string ("".to_string()).
Step 3
Run the test again.
This time, code compilation will pass and we receive actual test failures.
running 3 tests
test test_other_same_name ... ignored
test test_sample_name ... ignored
test test_no_name ... FAILED
failures:
---- test_no_name stdout ----
thread 'test_no_name' panicked at 'assertion failed: `(left == right)`
(left: `"Hello, World!"`, right: `""`)', tests/hello-world.rs:5
failures:
test_no_name
test result: FAILED. 0 passed; 1 failed; 2 ignored; 0 measured
Understanding Test Failures
Only one of the tests runs (test_no_name) and it fails. The other
tests are ignored (more on that later).
The test_no_name failure states that it is expecting the value,
"Hello, World!", to be returned from hello("").
The left side of the assertion (at line 5) should be equal to the right side.
---- test_no_name stdout ----
thread 'test_no_name' panicked at 'assertion failed: `(left == right)`
(left: `"Hello, World!"`, right: `""`)', tests/hello-world.rs:5
To fix it, let's return "Hello, World!", instead of an empty string
("") inside our hello function.
pub fn hello(name: Option<&str>) -> String {
"Hello, World!".to_string()
}
Step 4
Run the test again. This time, it will pass.
running 3 tests
test test_other_same_name ... ignored
test test_sample_name ... ignored
test test_no_name ... ok
test result: ok. 1 passed; 0 failed; 2 ignored; 0 measured
Doc-tests hello-world
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured
You may have noticed compiler warnings earlier:
Compiling hello-world v0.0.0
(file:////exercism/exercises/rust/hello-world)
src/lib.rs:1:14: 1:18 warning: unused variable: `name`, #[warn(unused_variables)] on by default
src/lib.rs:1 pub fn hello(name: Option<&str>) -> String {
^~~~
Our hello function does not use the name argument so the
compiler is letting us know that we could potentially remove the
argument from our function (it likes "clean code").
As we make the rest of the tests pass, we will find that we need the name
argument, so don't delete it.
Activate the next test. Open the tests/hello-world.rs file.
Delete the #[ignore] line for the test_sample_name test.
Step 5
Run the test suite again. Read the test failure and make the test pass.
As a reminder, the rust book
is a good reference for understanding rust.
The cargo output may also have hints to help you, depending on the errors you get.
For example, rustc --explain E0425 will explain unresolved name errors.
Wash, Rinse, Repeat
Delete one #[ignore] at a time, and make each test pass before you move to
the next one.
Submit
When everything is passing, you can submit your code with the following command:
$ exercism submit src/lib.rs