feat: exit with 101 from forc-test if there are failing tests (FuelLa…

…bs#4463)

## Description
closes FuelLabs#4462.

With this PR we exit from `forc test` with 101 exit status, if there are
failing unit tests. If `forc test` execution itself fails we exit with
1. This is useful especially in CIs as the return status can be checked
to better understand what is happening.

## Checklist

- [x] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [x] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [ ] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [ ] I have requested a review from the relevant team or maintainers.

---------

Co-authored-by: Sophie Dankel <[email protected]>

docs/book/src/testing/unit-testing.md

@@ -15,6 +15,8 @@ Each test function is ran as if it were the entry point for a
 [script](../sway-program-types/scripts.md). Tests "pass" if they return
 successfully, and "fail" if they revert or vice versa while [testing failure](#testing-failure).
 
+If the project has failing tests `forc test` will exit with exit status `101`.
+
 ## Building and Running Tests
 
 We can build and execute all tests within a package with the following:

forc-util/src/lib.rs

@@ -52,6 +52,14 @@ impl ForcError {
     pub fn new(error: anyhow::Error, exit_code: u8) -> Self {
         Self { error, exit_code }
     }
+
+    /// Returns a `ForcError` with provided exit_code.
+    pub fn exit_code(self, exit_code: u8) -> Self {
+        Self {
+            error: self.error,
+            exit_code,
+        }
+    }
 }
 
 impl AsRef<anyhow::Error> for ForcError {

forc/src/cli/commands/test.rs

@@ -3,7 +3,7 @@ use ansi_term::Colour;
 use clap::Parser;
 use forc_pkg as pkg;
 use forc_test::{TestRunnerCount, TestedPackage};
-use forc_util::{forc_result_bail, format_log_receipts, ForcResult};
+use forc_util::{forc_result_bail, format_log_receipts, ForcError, ForcResult};
 use tracing::info;
 
 /// Run the Sway unit tests for the current project.
@@ -86,7 +86,9 @@ pub(crate) fn exec(cmd: Command) -> ForcResult<()> {
     if all_tests_passed {
         Ok(())
     } else {
-        Err("Some tests failed.".into())
+        let forc_error: ForcError = "Some tests failed.".into();
+        const FAILING_UNIT_TESTS_EXIT_CODE: u8 = 101;
+        Err(forc_error.exit_code(FAILING_UNIT_TESTS_EXIT_CODE))
     }
 }