diff --git a/pttodoest/src/main.rs b/pttodoest/src/main.rs
index c3b4af5..c41a9d6 100755
--- a/pttodoest/src/main.rs
+++ b/pttodoest/src/main.rs
@@ -620,4 +620,32 @@ mod edit {
 
         Ok(())
     }
+
+    #[cfg(test)]
+    mod test_edit {
+        use super::*;
+
+        #[test]
+        fn test_build_empty() {
+            tests::with_dir(|d| {
+                build_dir(&d, &Files { files: vec![] }).expect("failed to build empty dir");
+            });
+        }
+
+        #[test]
+        fn test_build_with_files() {
+            tests::with_dir(|d1| {
+                tests::write_file(&d1, "file_a", "hello world a");
+                tests::write_file(&d1, "file_b", "hello world b");
+                let p1 = d1.path().join("file_a").display().to_string();
+                let p2 = d1.path().join("file_b").display().to_string();
+                let files = Files::new(&vec![p1, p2]);
+                tests::with_dir(|d2| {
+                    build_dir(&d2, &files).expect("failed to build non-empty dir");
+                    tests::file_contains(&d2, "file_a", "hello world a");
+                    tests::file_contains(&d2, "file_b", "hello world b");
+                });
+            });
+        }
+    }
 }