libcnb-test: Check the exit code of pack sbom download

CHANGELOG.md

@@ -6,6 +6,10 @@ separate changelogs for each crate were used. If you need to refer to these old
 
 ## [Unreleased]
 
+### Fixed
+
+- libcnb-test: `TestContext::download_sbom_files` now checks the exit code of the `pack sbom download` command it runs. ([#520](https://github.com/heroku/libcnb.rs/pull/520))
+
 ### Changed
 
 - libcnb: Drop the use of the `stacker` crate when recursively removing layer directories. ([#517](https://github.com/heroku/libcnb.rs/pull/517))

libcnb-test/src/pack.rs

@@ -1,6 +1,7 @@
+use crate::PackResult;
 use std::collections::BTreeMap;
 use std::path::PathBuf;
-use std::process::{Command, Output, Stdio};
+use std::process::{Command, Output};
 use tempfile::TempDir;
 
 /// Represents a `pack build` command.
@@ -175,22 +176,41 @@ impl From<PackSbomDownloadCommand> for Command {
     }
 }
 
-/// Runs the given pack command, panicking with user-friendly error messages when errors occur and
-/// pipes through stdout and stderr.
-pub(crate) fn run_pack_command<C: Into<Command>>(command: C) -> Output {
-    command.into()
-        .stdout(Stdio::piped())
-        .stderr(Stdio::piped())
-        .spawn()
+/// Runs the given pack command, panicking with user-friendly error messages when errors occur.
+pub(crate) fn run_pack_command<C: Into<Command>>(
+    command: C,
+    expected_result: &PackResult,
+) -> Output {
+    let output = command.into()
+        .output()
         .unwrap_or_else(|io_error| {
             if io_error.kind() == std::io::ErrorKind::NotFound {
                 panic!("External `pack` command not found. Install Pack CLI and ensure it is on PATH: https://buildpacks.io/docs/install-pack");
             } else {
                 panic!("Could not spawn external `pack` process: {io_error}");
             };
-        })
-        .wait_with_output()
-        .expect("Error while waiting on external `pack` process")
+        });
+
+    if (expected_result == &PackResult::Success && !output.status.success())
+        || (expected_result == &PackResult::Failure && output.status.success())
+    {
+        panic!(
+            "pack command unexpectedly {} with exit-code {}!\n\npack stdout:\n{}\n\npack stderr:\n{}",
+            if output.status.success() {
+                "succeeded"
+            } else {
+                "failed"
+            },
+            output
+                .status
+                .code()
+                .map_or(String::from("<unknown>"), |exit_code| exit_code.to_string()),
+            String::from_utf8_lossy(&output.stdout),
+            String::from_utf8_lossy(&output.stderr)
+        );
+    }
+
+    output
 }
 
 #[cfg(test)]

libcnb-test/src/test_context.rs

@@ -1,7 +1,7 @@
 use crate::pack::{run_pack_command, PackSbomDownloadCommand};
 use crate::{
     container_port_mapping, util, BuildConfig, ContainerConfig, ContainerContext, LogOutput,
-    TestRunner,
+    PackResult, TestRunner,
 };
 use bollard::container::{Config, CreateContainerOptions, StartContainerOptions};
 use bollard::image::RemoveImageOptions;
@@ -202,7 +202,7 @@ impl<'a> TestContext<'a> {
         let mut command = PackSbomDownloadCommand::new(&self.image_name);
         command.output_dir(temp_dir.path());
 
-        run_pack_command(command);
+        run_pack_command(command, &PackResult::Success);
 
         f(SbomFiles {
             sbom_files_directory: temp_dir.path().into(),

libcnb-test/src/test_runner.rs

@@ -1,5 +1,5 @@
 use crate::pack::{run_pack_command, PackBuildCommand};
-use crate::{app, build, util, BuildConfig, BuildpackReference, PackResult, TestContext};
+use crate::{app, build, util, BuildConfig, BuildpackReference, TestContext};
 use bollard::Docker;
 use std::borrow::Borrow;
 use std::env;
@@ -156,7 +156,7 @@ impl TestRunner {
             };
         }
 
-        let output = run_pack_command(pack_command);
+        let output = run_pack_command(pack_command, &config.expected_pack_result);
 
         let test_context = TestContext {
             pack_stdout: String::from_utf8_lossy(&output.stdout).into_owned(),
@@ -166,21 +166,6 @@ impl TestRunner {
             runner: self,
         };
 
-        if (config.expected_pack_result == PackResult::Failure && output.status.success())
-            || (config.expected_pack_result == PackResult::Success && !output.status.success())
-        {
-            panic!(
-                "pack command unexpectedly {} with exit-code {}!\n\npack stdout:\n{}\n\npack stderr:\n{}",
-                if output.status.success() { "succeeded" } else { "failed" },
-                output
-                    .status
-                    .code()
-                    .map_or(String::from("<unknown>"), |exit_code| exit_code.to_string()),
-                test_context.pack_stdout,
-                test_context.pack_stderr
-            );
-        } else {
-            f(test_context);
-        }
+        f(test_context);
     }
 }