fix(tests): Harden CLI tests

The new traces are not safe against re-running with an overlapping source
and dest dir.  Ideally, we'd generate to tempdir's anyways but then the paths are
different, breaking traces.  So, in the end, we'd just mirroring the same
test between `trace` and `trace_alias`.

tests/cli.rs

@@ -1,14 +1,15 @@
 #[macro_use]
-extern crate difference;
-#[macro_use]
 extern crate assert_cli;
 #[macro_use]
 extern crate lazy_static;
+extern crate tempdir;
 
 use std::env;
 use std::str;
 use std::path::{Path, PathBuf};
 
+use tempdir::TempDir;
+
 static EMPTY: &'static [&'static str] = &[];
 lazy_static! {
     static ref _CWD: PathBuf = env::current_dir().unwrap();
@@ -46,41 +47,115 @@ pub fn invalid_calls() {
 }
 
 #[test]
-pub fn log_levels() {
+pub fn log_levels_trace() {
     env::set_current_dir(CWD.join("tests/fixtures/example")).unwrap();
 
-    let output1 = assert_cli!(&BIN, &["build", "--trace"] => Success).unwrap();
-    let output1_stderr = str::from_utf8(&output1.stderr).to_owned().unwrap();
+    let destdir = TempDir::new("trace").expect("Tempdir not created");
+    let dest_param = destdir
+        .path()
+        .to_str()
+        .expect("Can't convert destdir to str")
+        .to_owned();
+
+    let output1 = assert_cli!(&BIN, &["build", "-L", "trace", "-d", &dest_param] => Success)
+        .unwrap();
     assert_contains!(&output1.stderr, "[trace]");
     assert_contains!(&output1.stderr, "[debug]");
     assert_contains!(&output1.stderr, "[info]");
 
-    let output2 = assert_cli!(&BIN, &["build", "-L", "trace"] => Success).unwrap();
-    let output2_stderr = str::from_utf8(&output2.stderr).to_owned().unwrap();
-    assert_diff!(&output1_stderr, &output2_stderr, " ", 0);
+    destdir.close().unwrap();
+}
+
+#[test]
+pub fn log_levels_trace_alias() {
+    env::set_current_dir(CWD.join("tests/fixtures/example")).unwrap();
+
+    let destdir = TempDir::new("trace_alias").expect("Tempdir not created");
+    let dest_param = destdir
+        .path()
+        .to_str()
+        .expect("Can't convert destdir to str")
+        .to_owned();
+
+    let output1 = assert_cli!(&BIN, &["build", "--trace", "-d", &dest_param] => Success).unwrap();
+    assert_contains!(&output1.stderr, "[trace]");
+    assert_contains!(&output1.stderr, "[debug]");
+    assert_contains!(&output1.stderr, "[info]");
+
+    destdir.close().unwrap();
+}
+
+#[test]
+pub fn log_levels_debug() {
+    env::set_current_dir(CWD.join("tests/fixtures/example")).unwrap();
 
-    let output = assert_cli!(&BIN, &["build", "-L", "debug"] => Success).unwrap();
+    let destdir = TempDir::new("debug").expect("Tempdir not created");
+    let dest_param = destdir
+        .path()
+        .to_str()
+        .expect("Can't convert destdir to str")
+        .to_owned();
+
+    let output = assert_cli!(&BIN, &["build", "-L", "debug", "-d", &dest_param] => Success)
+        .unwrap();
     assert_contains_not!(&output.stderr, "[trace]");
     assert_contains!(&output.stderr, "[debug]");
     assert_contains!(&output.stderr, "[info]");
 
-    let output = assert_cli!(&BIN, &["build", "-L", "info"] => Success).unwrap();
+    destdir.close().unwrap();
+}
+
+#[test]
+pub fn log_levels_info() {
+    env::set_current_dir(CWD.join("tests/fixtures/example")).unwrap();
+
+    let destdir = TempDir::new("info").expect("Tempdir not created");
+    let dest_param = destdir
+        .path()
+        .to_str()
+        .expect("Can't convert destdir to str")
+        .to_owned();
+
+    let output = assert_cli!(&BIN, &["build", "-L", "info", "-d", &dest_param] => Success).unwrap();
     assert_contains_not!(&output.stderr, "[trace]");
     assert_contains_not!(&output.stderr, "[debug]");
     assert_contains!(&output.stderr, "[info]");
 
-    assert_cli!(&BIN, &["build", "--silent"] => Success, "").unwrap();
+    destdir.close().unwrap();
+}
+
+#[test]
+pub fn log_levels_silent() {
+    env::set_current_dir(CWD.join("tests/fixtures/example")).unwrap();
+
+    let destdir = TempDir::new("silent").expect("Tempdir not created");
+    let dest_param = destdir
+        .path()
+        .to_str()
+        .expect("Can't convert destdir to str")
+        .to_owned();
+
+    assert_cli!(&BIN, &["build", "--silent", "-d", &dest_param] => Success, "").unwrap();
+
+    destdir.close().unwrap();
 }
 
 #[test]
 pub fn clean() {
     env::set_current_dir(CWD.join("tests/fixtures/example")).unwrap();
-    assert_cli!(&BIN, &["build", "-d", "./test_dest"] => Success).unwrap();
-    assert_eq!(Path::new("./test_dest/").is_dir(), true);
 
-    let output = assert_cli!(&BIN, &["clean", "-d", "./test_dest"] => Success).unwrap();
-    assert_eq!(Path::new("./test_dest").is_dir(), false);
-    assert_contains!(&output.stderr, "directory \"./test_dest\" removed");
+    let destdir = TempDir::new("clean").expect("Tempdir not created");
+    let dest_param = destdir
+        .path()
+        .to_str()
+        .expect("Can't convert destdir to str")
+        .to_owned();
+
+    assert_cli!(&BIN, &["build", "-d", &dest_param] => Success).unwrap();
+    assert_eq!(destdir.path().is_dir(), true);
+
+    assert_cli!(&BIN, &["clean", "-d", &dest_param] => Success).unwrap();
+    assert_eq!(destdir.path().is_dir(), false);
 }
 
 #[cfg(not(windows))]