Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

crates/nu-command/tests/commands/math/median.rs

@@ -0,0 +1,40 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn median_numbers_with_even_rows() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+             echo [10 6 19 21 4]
+             | math median
+         "#
+    ));
+
+    assert_eq!(actual.out, "10")
+}
+
+#[test]
+fn median_numbers_with_odd_rows() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+             echo [3 8 9 12 12 15]
+             | math median
+         "#
+    ));
+
+    assert_eq!(actual.out, "10.5")
+}
+
+#[test]
+fn median_mixed_numbers() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+             echo [-11.5 -13.5 10]
+             | math median
+         "#
+    ));
+
+    assert_eq!(actual.out, "-11.5")
+}