expect success by default + cleanup

Author: colin-kiegel

src/errors.rs

@@ -1,4 +1,4 @@
-static ERROR_PREFIX: &'static str = "CLI assertion failed";
+const ERROR_PREFIX: &'static str = "CLI assertion failed";
 
 error_chain! {
     foreign_links {

src/lib.rs

@@ -138,7 +138,7 @@ impl std::default::Default for Assert {
         Assert {
             cmd: vec!["cargo", "run", "--"]
                 .into_iter().map(String::from).collect(),
-            expect_success: None,
+            expect_success: Some(true),
             expect_exit_code: None,
             expect_stdout: None,
             expect_stderr: None,