fixtures verify test setups are resolved correctly by node runtime

.github/workflows/verify.yml

@@ -54,6 +54,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
       - uses: dtolnay/rust-toolchain@stable
       - uses: swatinem/rust-cache@v2
       - name: cargo test

fn_build/src/testing.rs

@@ -9,8 +9,9 @@ use std::collections::HashMap;
 use std::future::Future;
 use std::path::{Path, PathBuf};
 use std::pin::Pin;
+use std::process::{Command, Output};
 use std::sync::Arc;
-use std::{env, fs};
+use std::{env, fs, io};
 use temp_dir::TempDir;
 
 #[allow(unused)]
@@ -68,6 +69,15 @@ impl BuildProcess for JavaScriptBuild {
     fn runtime_config(&self, project_dir: &Path) -> Runtime {
         Runtime::Node(NodeConfig::read_node_config(&project_dir).unwrap())
     }
+
+    fn verify_runtime(&self, project_dir: &Path, entrypoint: &Path) -> Option<io::Result<Output>> {
+        Some(
+            Command::new("node")
+                .arg(entrypoint)
+                .current_dir(project_dir)
+                .output(),
+        )
+    }
 }
 
 #[derive(Deserialize, Serialize)]
@@ -111,6 +121,8 @@ trait BuildProcess {
     fn parse(&self, parse_spec: FnParseSpec) -> BuildProcessResult<FnManifest>;
 
     fn runtime_config(&self, project_dir: &Path) -> Runtime;
+
+    fn verify_runtime(&self, project_dir: &Path, entrypoint: &Path) -> Option<io::Result<Output>>;
 }
 
 fn collect_fixture_dirs(p: PathBuf) -> Vec<PathBuf> {
@@ -159,6 +171,7 @@ impl TestFixture {
     }
 
     async fn test(&self) -> Result<(), anyhow::Error> {
+        self.runtime_verify_fixture().await?;
         let temp_build_dir = TempDir::new()?;
         let build_dir_root = temp_build_dir.path().to_path_buf();
         if self.leak_build_dir {
@@ -183,6 +196,27 @@ impl TestFixture {
         Ok(())
     }
 
+    async fn runtime_verify_fixture(&self) -> Result<(), anyhow::Error> {
+        if let Some(result) = self
+            .build_process
+            .verify_runtime(&self.fixture_dir, &self.spec.entrypoint)
+        {
+            let output = result?;
+            if !output.status.success() {
+                panic!(
+                    "fixture {} failed verifying with runtime with output:\n{}",
+                    self.fixture_label(),
+                    format!(
+                        "~~STDERR~~\n{}\n~~STDOUT~~\n{}",
+                        String::from_utf8(output.stderr)?,
+                        String::from_utf8(output.stdout)?,
+                    )
+                );
+            }
+        }
+        Ok(())
+    }
+
     async fn build(&self, build_dir: PathBuf, build_mode: BuildMode) -> Result<(), anyhow::Error> {
         self.build_process
             .build(FnBuildSpec {