carols10cents/cargo-open

Add a test for trying to open a crate that has not yet been downloaded

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#5 opened on Oct 4, 2015

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E-easyhelp wanted

Description

In main.rs, add a unit test for the cargo_dir function that checks that it panics if we have specified a new crate in the Cargo.toml file but have not yet run any command that would fetch that crate's source to our local filesystem.

Use the existing test marked should_panic for an example of how to make a test check that a function panics.

As I write this up, I'm seeing that it would be easier if a function to read the Cargo.toml contents was extracted from the cargo_dir function and, instead, cargo_dir took the contents of Cargo.toml as an argument. That would make it easier to pass different Cargo.toml contents in for a unit test, so that should be part of this issue and should be done before adding the test.

I'd accept a PR that adds this test even if it fails, or if it fails with a weird error message! I'm not sure if I've coded things in such a way as to reuse existing cargo knowledge or not. Eventually I'd like this to panic with a message like "This crate has not been fetched yet; please run cargo install" first.

Bonus points if you change the code to make the test pass!

Contributor guide

Tech stack
rust
Domain
testing
Issue type
test
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Rust testing basicsunderstanding of cargo dir function
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
First, examine the existing `cargo dir` function in `main.rs` and the `should panic` test example. Extract the part that reads `Cargo.toml` into a separate function. Then write a unit test that calls the new function with a `Cargo.toml` that has a crate not yet fetched, and assert that it panics with an appropriate message. The maintainer suggested a panic message like 'This crate has not been fetched yet; please run `cargo install`'.