Fix xtests build.

Author: SSheldon

xtests/build.py

@@ -40,8 +40,13 @@ def read_all_tests(src_files):
         for name, test in read_tests(filename):
             yield name, test
 
+def list_src_files(src_dir):
+    for root, _, files in os.walk(src_dir):
+        for filename in files:
+            yield os.path.join(root, filename)
+
 if __name__ == '__main__':
-    src_files = [os.path.join(SRC_DIR, f) for f in os.listdir(SRC_DIR)]
+    src_files = list(list_src_files(SRC_DIR))
     output_file = os.path.join(TEST_DIR, 'tests.rs')
 
     if should_build(output_file, src_files):

xtests/build.rs

@@ -1,5 +1,6 @@
 use std::process::Command;
 
 fn main() {
-    Command::new("python").arg("build.py").status().unwrap();
+    let status = Command::new("python").arg("build.py").status().unwrap();
+    assert!(status.success());
 }

xtests/lib.rs

@@ -3,8 +3,6 @@ extern crate objc;
 
 pub use objc::*;
 
-#[path = "../src/id.rs"]
-mod id;
 #[path = "../src/test_utils.rs"]
 mod test_utils;