Add initial nu-test-support port (#913)

* Add initial nu-test-support port

* finish changing binary name

* Oops, these aren't Windows-safe tests

crates/nu-test-support/src/lib.rs

@@ -0,0 +1,70 @@
+pub mod commands;
+pub mod fs;
+pub mod macros;
+pub mod playground;
+
+pub struct Outcome {
+    pub out: String,
+    pub err: String,
+}
+
+#[cfg(windows)]
+pub const NATIVE_PATH_ENV_VAR: &str = "Path";
+#[cfg(not(windows))]
+pub const NATIVE_PATH_ENV_VAR: &str = "PATH";
+
+#[cfg(windows)]
+pub const NATIVE_PATH_ENV_SEPARATOR: char = ';';
+#[cfg(not(windows))]
+pub const NATIVE_PATH_ENV_SEPARATOR: char = ':';
+
+impl Outcome {
+    pub fn new(out: String, err: String) -> Outcome {
+        Outcome { out, err }
+    }
+}
+
+pub fn pipeline(commands: &str) -> String {
+    commands
+        .lines()
+        .skip(1)
+        .map(|line| line.trim())
+        .collect::<Vec<&str>>()
+        .join(" ")
+        .trim_end()
+        .to_string()
+}
+
+pub fn shell_os_paths() -> Vec<std::path::PathBuf> {
+    let mut original_paths = vec![];
+
+    if let Some(paths) = std::env::var_os(NATIVE_PATH_ENV_VAR) {
+        original_paths = std::env::split_paths(&paths).collect::<Vec<_>>();
+    }
+
+    original_paths
+}
+
+#[cfg(test)]
+mod tests {
+    use super::pipeline;
+
+    #[test]
+    fn constructs_a_pipeline() {
+        let actual = pipeline(
+            r#"
+                open los_tres_amigos.txt
+                | from-csv
+                | get rusty_luck
+                | str to-int
+                | math sum
+                | echo "$it"
+            "#,
+        );
+
+        assert_eq!(
+            actual,
+            r#"open los_tres_amigos.txt | from-csv | get rusty_luck | str to-int | math sum | echo "$it""#
+        );
+    }
+}