diff --git a/src/util.rs b/src/util.rs
index ac0dc59..12d03e2 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -15,3 +15,32 @@ pub fn write_file(path: &PathBuf, contents: &str) -> Result<()> {
     file.write_all(contents.as_bytes())?;
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn read_files() {
+        assert_eq!(
+            read_file(&PathBuf::from("tests/data/empty.txt")).unwrap(),
+            String::from("")
+        );
+        assert_eq!(
+            read_file(&PathBuf::from("tests/data/lines.txt")).unwrap(),
+            String::from("foo\nbar baz\n")
+        );
+    }
+
+    #[test]
+    fn write_files() {
+        assert_eq!(
+            write_file(&PathBuf::from("tests/data/empty.txt")),
+            String::from("")
+        );
+        assert_eq!(
+            write_file(&PathBuf::from("tests/data/lines.txt")),
+            String::from("foo\nbar baz\n")
+        );
+    }
+}
diff --git a/tests/data/empty.txt b/tests/data/empty.txt
new file mode 100644
index 0000000..e69de29
diff --git a/tests/data/lines.txt b/tests/data/lines.txt
new file mode 100644
index 0000000..089eeac
--- /dev/null
+++ b/tests/data/lines.txt
@@ -0,0 +1,2 @@
+foo
+bar baz