#include <assert.h>

struct test {
  int foo;
};
typedef struct test test_t;

int main(int argc, char *argv[]) {
  test_t a = { 23 };
  test_t b = { 42 };

  a = b;
  assert(a.foo == 42);
  assert(b.foo == 42);

  a.foo = 69;
  assert(a.foo == 69);
  assert(b.foo == 42);
}