fix: spawn_test never raises — coerce env/command to str, wrap unexpected errors (#34)

Closes #34

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_core.py

@@ -326,6 +326,42 @@ def test_spawn_test_large_stderr_does_not_deadlock():
     assert len(r["stderr"]) <= c._STDERR_CAP
 
 
+def test_spawn_test_non_string_env_value():
+    # Pasted JSON can carry numeric env values ("env": {"PORT": 8080}) that never
+    # round-trip through the editor. Popen rejects non-str env; spawn_test must
+    # coerce instead of letting TypeError escape (which would leave the GUI's
+    # Test launch / Test all buttons stuck disabled).
+    r = c.spawn_test(
+        {
+            "command": sys.executable,
+            "args": ["-c", "import os; raise SystemExit(0 if os.environ['PORT'] == '8080' else 1)"],
+            "env": {"PORT": 8080},
+        },
+        timeout=2.0,
+    )
+    assert r["outcome"] == "exited"
+    assert r["returncode"] == 0
+
+
+def test_spawn_test_non_string_command():
+    # A non-string command must classify, not raise (str(123) resolves to nothing).
+    r = c.spawn_test({"command": 123}, timeout=0.3)
+    assert r["outcome"] == "not_found"
+
+
+def test_spawn_test_internal_error_yields_result(monkeypatch):
+    # Any unexpected exception inside the spawn path must come back as a result
+    # dict (outcome "error"), never escape — the UI only re-enables its buttons
+    # when a result arrives.
+    def boom(*a, **k):
+        raise RuntimeError("simulated internal failure")
+
+    monkeypatch.setattr(c.shutil, "which", boom)
+    r = c.spawn_test({"command": "python3"}, timeout=0.3)
+    assert r["outcome"] == "error"
+    assert "simulated internal failure" in r["detail"]
+
+
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