Show more context on exit code failures

stdout and stderr will now be shown when the exit code is an unexpected
value.  This will serve to provide additional context for the developer
without them having to fire up a debugger or manually reproduce the
failure condition.

Author: epage

src/assert.rs

@@ -241,19 +241,27 @@ impl Assert {
 
         if let Some(expect_success) = self.expect_success {
             if expect_success != output.status.success() {
+                let out = String::from_utf8_lossy(&output.stdout).to_string();
+                let err = String::from_utf8_lossy(&output.stderr).to_string();
                 bail!(ErrorKind::StatusMismatch(
                     self.cmd.clone(),
                     expect_success,
+                    out,
+                    err,
                 ));
             }
         }
 
         if self.expect_exit_code.is_some() &&
             self.expect_exit_code != output.status.code() {
+            let out = String::from_utf8_lossy(&output.stdout).to_string();
+            let err = String::from_utf8_lossy(&output.stderr).to_string();
             bail!(ErrorKind::ExitCodeMismatch(
                 self.cmd.clone(),
                 self.expect_exit_code,
                 output.status.code(),
+                out,
+                err,
             ));
         }
 

src/errors.rs

@@ -6,24 +6,28 @@ error_chain! {
         Fmt(::std::fmt::Error);
     }
     errors {
-        StatusMismatch(cmd: Vec<String>, expected: bool) {
+        StatusMismatch(cmd: Vec<String>, expected: bool, out: String, err: String) {
             description("Wrong status")
             display(
-                "{}: (command `{}` expected to {}) (command {})",
+                "{}: (command `{}` expected to {})\nstatus={}\nstdout=```{}```\nstderr=```{}```",
                 ERROR_PREFIX,
                 cmd.join(" "),
                 expected = if *expected { "succeed" } else { "fail" },
                 got = if *expected { "failed" } else { "succeeded" },
+                out = out,
+                err = err,
             )
         }
-        ExitCodeMismatch(cmd: Vec<String>, expected: Option<i32>, got: Option<i32>) {
+        ExitCodeMismatch(cmd: Vec<String>, expected: Option<i32>, got: Option<i32>, out: String, err: String) {
             description("Wrong exit code")
             display(
-                "{}: (exit code of `{}` expected to be `{:?}`) (exit code was: `{:?}`)",
+                "{}: (exit code of `{}` expected to be `{:?}`)\nexit code=`{:?}`\nstdout=```{}```\nstderr=```{}```",
                 ERROR_PREFIX,
                 cmd.join(" "),
                 expected,
                 got,
+                out,
+                err,
             )
         }
         StdoutMismatch(cmd: Vec<String>, output_err: ::output::Error) {