Add a simple passing test for diffs.

1 files changed, 20 insertions, 0 deletions

diff --git a/src/rustfmt_diff.rs b/src/rustfmt_diff.rs
index 3fb22865385..6884e39141d 100644
--- a/src/rustfmt_diff.rs
+++ b/src/rustfmt_diff.rs
@@ -162,3 +162,23 @@ where
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::{make_diff,Mismatch};
+    use super::DiffLine::*;
+
+    #[test]
+    fn simple_diff() {
+        let src = "one\ntwo\nthree\nfour\nfive\n";
+        let dest= "one\ntwo\ntrois\nfour\nfive\n";
+        let diff = make_diff(src, dest, 1);
+        assert_eq!(diff, vec![Mismatch { line_number: 2,
+                                         lines: vec![
+                                             Context("two".into()),
+                                             Resulting("three".into()),
+                                             Expected("trois".into()),
+                                             Context("four".into()),
+                                         ] }]);
+    }
+}
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