Make insert take in a block (#2265)

* Make insert take in a block

* Add some tests

crates/nu-cli/tests/commands/insert.rs

@@ -14,3 +14,27 @@ fn insert_plugin() {
 
     assert_eq!(actual.out, "1");
 }
+
+#[test]
+fn downcase_upcase() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        echo abcd | wrap downcase | insert upcase { echo $it.downcase | str upcase } | format "{downcase}{upcase}" 
+        "#
+    ));
+
+    assert_eq!(actual.out, "abcdABCD");
+}
+
+#[test]
+fn number_and_its_negative_equal_zero() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        echo 1..10 | wrap num | insert neg { = $it.num * -1 } | math sum | = $it.num + $it.neg
+        "#
+    ));
+
+    assert_eq!(actual.out, "0");
+}