test(harness): force unreachable proxy for spawned mozart

Composer fixtures with inline `package` repositories often set
`dist.url` / `source.url` to RFC 2606 placeholders like
`https://example.org`. Composer's PHPUnit suite swaps in
InstallationManagerMock; Mozart's harness invokes the real binary,
so its `reqwest`-based downloader actually hit the network and
hung for ~30s per fixture before failing.

Setting HTTP_PROXY / HTTPS_PROXY / NO_PROXY on the child process
routes every HTTP request through 127.0.0.1:1, which fails the
TCP connect immediately. The current 103 green installer tests
remain green (resolver short-circuits before download); the
ignored update_downgrades_unstable_packages now errors in 0.1s
instead of 30s, which is the safety net we want as more
inline-package fixtures get unignored.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/crates/mozart-test-harness/src/runner.rs b/crates/mozart-test-harness/src/runner.rs
index cefd50f..acff8b5 100644
--- a/crates/mozart-test-harness/src/runner.rs
+++ b/crates/mozart-test-harness/src/runner.rs
@@ -46,9 +46,17 @@ pub fn run_test(test: &ParsedTest, mozart_bin: &Path) -> Result<RunResult> {
     }
 
     let args: Vec<&str> = test.run.split_whitespace().collect();
+    // Force a non-routable proxy so any stray HTTP request from `mozart`
+    // (e.g. inline `package` fixtures whose dist.url points at example.org)
+    // fails fast instead of hitting the network. Composer's PHPUnit suite
+    // uses InstallationManagerMock; we can't mock the binary's HTTP client,
+    // but `reqwest` honors HTTP(S)_PROXY env vars by default.
     let output = Command::new(mozart_bin)
         .args(&args)
         .current_dir(root)
+        .env("HTTP_PROXY", "http://127.0.0.1:1")
+        .env("HTTPS_PROXY", "http://127.0.0.1:1")
+        .env("NO_PROXY", "")
         .output()
         .with_context(|| format!("failed to invoke {}", mozart_bin.display()))?;