SDK tests use a tempdir as STDB_PATH, rather than ~/.spacetime (#348)

We've had continual issues with test isolation when developing breaking changes.
This commit doesn't fully address those, but is a step in the right direction:
the SDK tests now create a tempdir as their `STDB_PATH`,
rather than using `~/.spacetime`.

Cargo.toml

@@ -157,7 +157,7 @@ syntect = { version = "5.0.0", default-features = false, features = [
 ] }
 tabled = "0.8.0"
 tempdir = "0.3.7"
-tempfile = "3.3"
+tempfile = "3.8"
 termcolor = "1.2.0"
 thiserror = "1.0.37"
 tokio = { version = "1.25.1", features = ["full"] }

crates/testing/Cargo.toml

@@ -19,6 +19,7 @@ duct.workspace = true
 lazy_static.workspace = true
 rand.workspace = true
 prost.workspace = true
+tempfile.workspace = true
 
 [dev-dependencies]
 serial_test.workspace = true

crates/testing/src/sdk.rs

@@ -7,11 +7,20 @@ use std::{collections::HashSet, fs::create_dir_all, sync::Mutex};
 use crate::invoke_cli;
 use crate::modules::{module_path, CompiledModule};
 use std::path::Path;
+use tempfile::TempDir;
 
 pub fn ensure_standalone_process() {
     lazy_static! {
-        static ref JOIN_HANDLE: Mutex<Option<JoinHandle<()>>> =
-            Mutex::new(Some(std::thread::spawn(|| invoke_cli(&["start"]))));
+        static ref JOIN_HANDLE: Mutex<Option<JoinHandle<()>>> = {
+            let stdb_path = TempDir::with_prefix("stdb-sdk-test")
+                .expect("Failed to create tempdir")
+                // TODO: This leaks the tempdir.
+                //       We need the tempdir to live for the duration of the process,
+                //       and all the options for post-`main` cleanup seem sketchy.
+                .into_path();
+            std::env::set_var("STDB_PATH", stdb_path);
+            Mutex::new(Some(std::thread::spawn(|| invoke_cli(&["start"]))))
+        };
     }
 
     let mut join_handle = JOIN_HANDLE.lock().unwrap();