Refactor and strengthen tests of `delta file_a file_b`

This does not reproduce bug #463 (at least, not reliably).

1 files changed, 33 insertions, 34 deletions

diff --git a/src/main.rs b/src/main.rs
index 36239b67..a5c789b9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -426,6 +426,7 @@ pub fn _list_syntax_themes_for_machines(writer: &mut dyn Write) -> std::io::Resu
 #[cfg(test)]
 mod main_tests {
     use super::*;
+    use std::fs;
     use std::io::{Cursor, Seek, SeekFrom};
 
     use crate::ansi;
@@ -487,55 +488,53 @@ mod main_tests {
     #[test]
     #[cfg_attr(target_os = "windows", ignore)]
     fn test_diff_same_empty_file() {
-        let config = integration_test_utils::make_config_from_args(&[]);
-        let mut writer = Cursor::new(vec![]);
-        let exit_code = diff(
-            Some(&PathBuf::from("/dev/null")),
-            Some(&PathBuf::from("/dev/null")),
-            &config,
-            &mut writer,
-        );
-        assert_eq!(exit_code, 0);
-        let mut s = String::new();
-        writer.seek(SeekFrom::Start(0)).unwrap();
-        writer.read_to_string(&mut s).unwrap();
-        assert!(s.is_empty());
+        _do_diff_test("/dev/null", "/dev/null", false, None);
     }
 
     #[test]
     #[cfg_attr(target_os = "windows", ignore)]
     fn test_diff_same_non_empty_file() {
-        let config = integration_test_utils::make_config_from_args(&[]);
-        let mut writer = Cursor::new(vec![]);
-        let exit_code = diff(
-            Some(&PathBuf::from("/etc/passwd")),
-            Some(&PathBuf::from("/etc/passwd")),
-            &config,
-            &mut writer,
-        );
-        assert_eq!(exit_code, 0);
-        let mut s = String::new();
-        writer.seek(SeekFrom::Start(0)).unwrap();
-        writer.read_to_string(&mut s).unwrap();
-        assert!(s.is_empty());
+        _do_diff_test("/etc/passwd", "/etc/passwd", false, None);
+    }
+
+    #[test]
+    #[cfg_attr(target_os = "windows", ignore)]
+    fn test_diff_empty_vs_non_empty_file() {
+        _do_diff_test("/dev/null", "/etc/passwd", true, Some("/etc/passwd"));
     }
 
     #[test]
     #[cfg_attr(target_os = "windows", ignore)]
-    fn test_diff_differing_files() {
+    fn test_diff_two_non_empty_files() {
+        _do_diff_test("/etc/group", "/etc/passwd", true, None);
+    }
+
+    fn _do_diff_test(file_a: &str, file_b: &str, expect_diff: bool, expected_diff: Option<&str>) {
         let config = integration_test_utils::make_config_from_args(&[]);
         let mut writer = Cursor::new(vec![]);
         let exit_code = diff(
-            Some(&PathBuf::from("/dev/null")),
-            Some(&PathBuf::from("/etc/passwd")),
+            Some(&PathBuf::from(file_a)),
+            Some(&PathBuf::from(file_b)),
             &config,
             &mut writer,
         );
-        assert_eq!(exit_code, 1);
+        let s = ansi::strip_ansi_codes(&_read_to_string(&mut writer));
+        if expect_diff {
+            assert_eq!(exit_code, 1);
+            assert!(s.contains(&format!("comparing: {} ⟶   {}\n", file_a, file_b)));
+            if let Some(expected_diff) = expected_diff {
+                assert!(s.contains(&fs::read_to_string(expected_diff).unwrap()));
+            }
+        } else {
+            assert_eq!(exit_code, 0);
+            assert!(s.is_empty());
+        }
+    }
+
+    fn _read_to_string(cursor: &mut Cursor<Vec<u8>>) -> String {
         let mut s = String::new();
-        writer.seek(SeekFrom::Start(0)).unwrap();
-        writer.read_to_string(&mut s).unwrap();
-        let s = ansi::strip_ansi_codes(&s);
-        assert!(s.contains("comparing: /dev/null ⟶   /etc/passwd\n"));
+        cursor.seek(SeekFrom::Start(0)).unwrap();
+        cursor.read_to_string(&mut s).unwrap();
+        s
     }
 }