example unit test

crates/nu-command/src/strings/build_string.rs

@@ -1,7 +1,7 @@
 use nu_engine::eval_expression;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EvaluationContext};
-use nu_protocol::{ShellError, Signature, SyntaxShape, Value};
+use nu_protocol::{Example, ShellError, Signature, Span, SyntaxShape, Value};
 
 pub struct BuildString;
 
@@ -18,6 +18,27 @@ impl Command for BuildString {
         Signature::build("build-string").rest("rest", SyntaxShape::String, "list of string")
     }
 
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                example: "build-string a b c",
+                description: "Builds a string from letters a b c",
+                result: Some(Value::String {
+                    val: "abc".to_string(),
+                    span: Span::unknown(),
+                }),
+            },
+            Example {
+                example: "build-string (1 + 2) = one ' ' plus ' ' two",
+                description: "Builds a string from letters a b c",
+                result: Some(Value::String {
+                    val: "3=one plus two".to_string(),
+                    span: Span::unknown(),
+                }),
+            },
+        ]
+    }
+
     fn run(
         &self,
         context: &EvaluationContext,
@@ -36,3 +57,15 @@ impl Command for BuildString {
         })
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(BuildString {})
+    }
+}