Rename spec -> test

'Test' is a lot more straightforward of a name.

test/tests.cc

@@ -0,0 +1,16 @@
+#include "test_helper.h"
+
+int main(int argc, char *argv[]) {
+  int seed;
+  const char *seed_env = getenv("TREE_SITTER_SEED");
+  if (seed_env) {
+    seed = atoi(seed_env);
+  } else {
+    seed = time(nullptr);
+  }
+
+  printf("Random seed: %d\n", seed);
+  srandom(seed);
+
+  return bandit::run(argc, argv);
+}