add test

demes/src/ffi.rs

@@ -1772,3 +1772,20 @@ fn test_deme_ancestry_iterator() {
         assert_eq!(&ancestors, &ancestors_from_deme);
     }
 }
+
+#[test]
+fn test_load_from_file() {
+    let filename = "demes-spec/examples/browning_america.yaml";
+    let file = std::fs::File::open(filename).unwrap();
+    let graph = crate::load(file).unwrap();
+    let mut graph_from_file: *mut Graph = std::ptr::null_mut();
+    let mut error = FFIError::default();
+
+    let c_filename = CString::new(filename.to_string()).unwrap();
+    let code = unsafe {
+        demes_graph_load_from_file(c_filename.as_ptr(), &mut error, &mut graph_from_file)
+    };
+    assert_eq!(code, 0);
+    assert_eq!(&graph, unsafe{graph_from_file.as_ref()}.unwrap());
+    unsafe{demes_graph_deallocate(graph_from_file)};
+}