Issue 1787 (#1827)

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

@@ -1,6 +1,7 @@
 use nu_test_support::fs::Stub::FileWithContentToBeTrimmed;
 use nu_test_support::playground::Playground;
 use nu_test_support::{nu, pipeline};
+use std::str::FromStr;
 
 #[test]
 fn all() {
@@ -60,3 +61,52 @@ fn outputs_zero_with_no_input() {
         assert_eq!(actual.out, "0");
     })
 }
+
+#[test]
+fn compute_sum_of_individual_row() -> Result<(), String> {
+    let answers_for_columns = [
+        ("cpu", 88.257434),
+        ("mem", 3032375296.),
+        ("virtual", 102579965952.),
+    ];
+    for (column_name, expected_value) in answers_for_columns.iter() {
+        let actual = nu!(
+            cwd: "tests/fixtures/formats/",
+            format!("open sample-ps-output.json | select {} | sum | get {}", column_name, column_name)
+        );
+        let result =
+            f64::from_str(&actual.out).map_err(|_| String::from("Failed to parse float."))?;
+        assert_eq!(result, *expected_value);
+    }
+    Ok(())
+}
+
+#[test]
+fn compute_sum_of_table() -> Result<(), String> {
+    let answers_for_columns = [
+        ("cpu", 88.257434),
+        ("mem", 3032375296.),
+        ("virtual", 102579965952.),
+    ];
+    for (column_name, expected_value) in answers_for_columns.iter() {
+        let actual = nu!(
+            cwd: "tests/fixtures/formats/",
+            format!("open sample-ps-output.json | select cpu mem virtual | sum | get {}", column_name)
+        );
+        let result =
+            f64::from_str(&actual.out).map_err(|_| String::from("Failed to parse float."))?;
+        assert_eq!(result, *expected_value);
+    }
+    Ok(())
+}
+
+#[test]
+fn sum_of_a_row_containing_a_table_is_an_error() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats/",
+        "open sample-sys-output.json | sum"
+    );
+    assert!(actual
+        .err
+        .contains("Attempted to compute the sum of a value that cannot be summed."));
+}