test: validate environment variables

Add a test to check that the environment is correctly set.

test-env.sh

@@ -0,0 +1,65 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+echo "=== Testing Nix Environment Variables ==="
+echo
+
+# Test NIX_PROFILES
+echo "NIX_PROFILES: ${NIX_PROFILES:-<not set>}"
+if [[ -n "${NIX_PROFILES:-}" ]]; then
+  echo "✓ NIX_PROFILES is set"
+else
+  echo "✗ NIX_PROFILES is not set"
+  exit 1
+fi
+
+# Test NIX_SSL_CERT_FILE
+echo "NIX_SSL_CERT_FILE: ${NIX_SSL_CERT_FILE:-<not set>}"
+if [[ -n "${NIX_SSL_CERT_FILE:-}" ]]; then
+  if [[ -f "$NIX_SSL_CERT_FILE" ]]; then
+    echo "✓ NIX_SSL_CERT_FILE is set and file exists"
+  else
+    echo "⚠ NIX_SSL_CERT_FILE is set but file does not exist: $NIX_SSL_CERT_FILE"
+  fi
+else
+  echo "⚠ NIX_SSL_CERT_FILE is not set (may be OK depending on system)"
+fi
+
+# Test PATH contains Nix paths
+echo "PATH: $PATH"
+if echo "$PATH" | grep -E -q "(\.nix-profile|nix/profile)"; then
+  echo "✓ PATH contains Nix paths"
+else
+  echo "✗ PATH does not contain Nix paths"
+  exit 1
+fi
+
+# Test NIX_PATH if set
+if [[ -n "${NIX_PATH:-}" ]]; then
+  echo "NIX_PATH: $NIX_PATH"
+  echo "✓ NIX_PATH is set"
+else
+  echo "NIX_PATH: <not set>"
+fi
+
+# Test TMPDIR
+echo "TMPDIR: ${TMPDIR:-<not set>}"
+if [[ -n "${TMPDIR:-}" ]]; then
+  echo "✓ TMPDIR is set"
+else
+  echo "⚠ TMPDIR is not set"
+fi
+
+echo
+echo "=== Testing Nix Command ==="
+if command -v nix >/dev/null 2>&1; then
+  echo "✓ nix command is available"
+  echo "Nix version: $(nix --version)"
+else
+  echo "✗ nix command is not available"
+  exit 1
+fi
+
+echo
+echo "=== Environment Setup Test Complete ==="