add more tests for new behavior

crates/nu-command/tests/commands/let_.rs

@@ -45,6 +45,13 @@ fn mut_takes_pipeline() {
     assert_eq!(actual.out, "11");
 }
 
+#[test]
+fn mut_takes_pipeline_with_declared_type() {
+    let actual = nu!(r#"mut x: list<string> = [] | append "hello world"; print $x.0"#);
+
+    assert_eq!(actual.out, "hello world");
+}
+
 #[test]
 fn mut_pipeline_allows_in() {
     let actual =

tests/const_/mod.rs

@@ -415,3 +415,9 @@ fn const_raw_string() {
     let actual = nu!(r#"const x = r#'abc'#; $x"#);
     assert_eq!(actual.out, "abc");
 }
+
+#[test]
+fn const_takes_pipeline() {
+    let actual = nu!(r#"const list = 'bar_baz_quux' | split row '_'; $list | length"#);
+    assert_eq!(actual.out, "3");
+}

tests/repl/test_parser.rs

@@ -295,6 +295,22 @@ fn assign_expressions() -> TestResult {
     )
 }
 
+#[test]
+fn assign_takes_pipeline() -> TestResult {
+    run_test(
+        r#"mut foo = 'bar'; $foo = $foo | str upcase | str reverse; $foo"#,
+        "RAB",
+    )
+}
+
+#[test]
+fn append_assign_takes_pipeline() -> TestResult {
+    run_test(
+        r#"mut foo = 'bar'; $foo ++= $foo | str upcase; $foo"#,
+        "barBAR",
+    )
+}
+
 #[test]
 fn string_interpolation_paren_test() -> TestResult {
     run_test(r#"$"('(')(')')""#, "()")