added test

assets/csv1.csv

@@ -1,3 +1,4 @@
 nr;text;flag
 123213;bla bal;1
 123123;second one;0
+77732;hahah;3

src/csv/compare.rs

@@ -118,3 +118,34 @@ fn find_diff(vec1: &[CsvLine], vec2: &[CsvLine], diff: &mut Vec<CsvLine>, params
     }
 }
 
+#[cfg(test)]
+mod test {
+    use std::{fs::File, io::BufReader, path::Path};
+
+    use crate::csv::compare::{compare, CsvLine, Params};
+
+    fn get_reader(file_path: String) -> BufReader<File> {
+        let path = Path::new(&file_path);
+        assert!(path.is_file());
+        let file = File::open(path);
+        match file {
+            Ok(_) => BufReader::new(file.unwrap()),
+            Err(_) => panic!("error, could not read file"),
+        }
+    }
+
+    #[test]
+    fn test_find_diff() {
+        let file1 = get_reader("./assets/csv1.csv".to_string());
+        let file2 = get_reader("./assets/csv2.csv".to_string());
+        let params: Params = Params {
+            delimiter: ';'.to_string(),
+            source: "./assets/csv1.csv".to_owned(),
+            compared: "./assets/csv1.csv".to_owned(),
+            column: 1,
+            output: Some("./assets/result.csv".to_owned()),
+        };
+        let result: Vec<CsvLine> = compare(file1, file2, &params);
+        assert_eq!(3, result.len());
+    }
+}