test: deepen and complete project-wide test coverage (#297)

* test: deepen coverage for health doctor provider and tunnels

* test: add broad trait and module re-export coverage

src/runtime/traits.rs

@@ -30,3 +30,74 @@ pub trait RuntimeAdapter: Send + Sync {
         workspace_dir: &Path,
     ) -> anyhow::Result<tokio::process::Command>;
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    struct DummyRuntime;
+
+    impl RuntimeAdapter for DummyRuntime {
+        fn name(&self) -> &str {
+            "dummy-runtime"
+        }
+
+        fn has_shell_access(&self) -> bool {
+            true
+        }
+
+        fn has_filesystem_access(&self) -> bool {
+            true
+        }
+
+        fn storage_path(&self) -> PathBuf {
+            PathBuf::from("/tmp/dummy-runtime")
+        }
+
+        fn supports_long_running(&self) -> bool {
+            true
+        }
+
+        fn build_shell_command(
+            &self,
+            command: &str,
+            workspace_dir: &Path,
+        ) -> anyhow::Result<tokio::process::Command> {
+            let mut cmd = tokio::process::Command::new("echo");
+            cmd.arg(command);
+            cmd.current_dir(workspace_dir);
+            Ok(cmd)
+        }
+    }
+
+    #[test]
+    fn default_memory_budget_is_zero() {
+        let runtime = DummyRuntime;
+        assert_eq!(runtime.memory_budget(), 0);
+    }
+
+    #[test]
+    fn runtime_reports_capabilities() {
+        let runtime = DummyRuntime;
+
+        assert_eq!(runtime.name(), "dummy-runtime");
+        assert!(runtime.has_shell_access());
+        assert!(runtime.has_filesystem_access());
+        assert!(runtime.supports_long_running());
+        assert_eq!(runtime.storage_path(), PathBuf::from("/tmp/dummy-runtime"));
+    }
+
+    #[tokio::test]
+    async fn build_shell_command_executes() {
+        let runtime = DummyRuntime;
+        let mut cmd = runtime
+            .build_shell_command("hello-runtime", Path::new("."))
+            .unwrap();
+
+        let output = cmd.output().await.unwrap();
+        let stdout = String::from_utf8_lossy(&output.stdout);
+
+        assert!(output.status.success());
+        assert!(stdout.contains("hello-runtime"));
+    }
+}