Add test for preserving line endings

Closes #77

Author: killercup

cargo-fix/tests/all/main.rs

@@ -2,8 +2,8 @@ extern crate difference;
 extern crate url;
 
 use std::env;
-use std::fs;
-use std::io::Write;
+use std::fs::{self, File};
+use std::io::{Read, Write};
 use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::str;
@@ -84,6 +84,15 @@ impl Project {
             cwd: None,
         }
     }
+
+    fn read(&self, path: &str) -> String {
+        let mut ret = String::new();
+        File::open(self.root.join(path))
+            .unwrap()
+            .read_to_string(&mut ret)
+            .unwrap();
+        return ret
+    }
 }
 
 struct ExpectCmd<'a> {

cargo-fix/tests/all/smoke.rs

@@ -87,3 +87,16 @@ fn tricky_ampersand() {
         .stderr(stderr)
         .run();
 }
+
+#[test]
+fn preserve_line_endings() {
+    let p = project()
+        .file("src/lib.rs", "\
+            fn add(a: &u32) -> u32 { a + 1 }\r\n\
+            pub fn foo() -> u32 { add(1) }\r\n\
+        ")
+        .build();
+
+    p.expect_cmd("cargo fix").run();
+    assert!(p.read("src/lib.rs").contains("\r\n"));
+}