basic test for the env feature

to see how it goes on all the tests platforms. Executing an external
program may not be easy with some cross platforms or on windows

tests/env.rs

@@ -0,0 +1,27 @@
+mod common;
+
+use assert_fs::fixture::PathChild;
+use common::*;
+use predicates::str::{contains, is_empty};
+
+const YAML_CONTENT: &str = "foo: bar";
+
+#[test]
+fn env() {
+    let tmp = temp_dir();
+    let (key_path, pub_path) = create_key(&tmp);
+    let yaml_path = tmp.child("file.yaml");
+    write(&yaml_path, YAML_CONTENT);
+    let encrypted_path = tmp.child("file.enc.yaml");
+    yage!(
+        "encrypt",
+        "-R",
+        &pub_path,
+        &yaml_path,
+        "-o",
+        &encrypted_path
+    );
+    yage!("env", "-K", &key_path, &encrypted_path, "env")
+        .stdout(contains("foo=bar"))
+        .stderr(is_empty());
+}