Add failing test: duplicated header when file renamed with changes

Reproduces bug #245

1 files changed, 45 insertions, 0 deletions

diff --git a/src/tests/test_utils.rs b/src/tests/test_utils.rs
new file mode 100644
index 00000000..054365d2
--- /dev/null
+++ b/src/tests/test_utils.rs
@@ -0,0 +1,45 @@
+#[cfg(test)]
+pub mod test_utils {
+    /// Return true iff `s` contains exactly one occurrence of substring `t`.
+    pub fn contains_once(s: &str, t: &str) -> bool {
+        match (s.find(t), s.rfind(t)) {
+            (Some(i), Some(j)) => i == j,
+            _ => false,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::test_utils::test_utils::*;
+
+    #[test]
+    fn test_contains_once_1() {
+        assert!(contains_once("", ""));
+    }
+
+    #[test]
+    fn test_contains_once_2() {
+        assert!(contains_once("a", "a"));
+    }
+
+    #[test]
+    fn test_contains_once_3() {
+        assert!(!contains_once("", "a"));
+    }
+
+    #[test]
+    fn test_contains_once_4() {
+        assert!(!contains_once("a", "b"));
+    }
+
+    #[test]
+    fn test_contains_once_5() {
+        assert!(!contains_once("a a", "a"));
+    }
+
+    #[test]
+    fn test_contains_once_6() {
+        assert!(contains_once("a b", "b"));
+    }
+}