nu-cli/completions: add variable completions test + refactor tests (#5504)

* refactor tests

* removed old test file

crates/nu-cli/tests/support/completions_helpers.rs

@@ -0,0 +1,105 @@
+use std::path::PathBuf;
+
+use nu_command::create_default_context;
+use nu_engine::eval_block;
+use nu_parser::parse;
+use nu_protocol::{
+    engine::{EngineState, Stack, StateDelta, StateWorkingSet},
+    PipelineData, Span, Value,
+};
+use nu_test_support::fs;
+use reedline::Suggestion;
+const SEP: char = std::path::MAIN_SEPARATOR;
+
+#[allow(dead_code)]
+// creates a new engine with the current path into the completions fixtures folder
+pub fn new_engine() -> (PathBuf, String, EngineState, Stack) {
+    // Target folder inside assets
+    let dir = fs::fixtures().join("completions");
+    let mut dir_str = dir
+        .clone()
+        .into_os_string()
+        .into_string()
+        .unwrap_or_default();
+    dir_str.push(SEP);
+
+    // Create a new engine with default context
+    let mut engine_state = create_default_context(&dir);
+
+    // New stack
+    let mut stack = Stack::new();
+
+    // New delta state
+    let delta = StateDelta::new(&engine_state);
+
+    // Add pwd as env var
+    stack.add_env_var(
+        "PWD".to_string(),
+        Value::String {
+            val: dir_str.clone(),
+            span: nu_protocol::Span {
+                start: 0,
+                end: dir_str.len(),
+            },
+        },
+    );
+
+    // Merge delta
+    let merge_result = engine_state.merge_delta(delta, Some(&mut stack), &dir);
+    assert!(merge_result.is_ok());
+
+    // Add record value as example
+    let record = "let actor = { name: 'Tom Hardy', age: 44 }";
+    let (block, delta) = {
+        let mut working_set = StateWorkingSet::new(&engine_state);
+
+        let (block, err) = parse(&mut working_set, None, record.as_bytes(), false, &[]);
+
+        assert!(err.is_none());
+
+        (block, working_set.render())
+    };
+    assert!(eval_block(
+        &engine_state,
+        &mut stack,
+        &block,
+        PipelineData::Value(
+            Value::Nothing {
+                span: Span { start: 0, end: 0 },
+            },
+            None
+        ),
+        false,
+        false
+    )
+    .is_ok());
+
+    // Merge delta
+    let merge_result = engine_state.merge_delta(delta, Some(&mut stack), &dir);
+    assert!(merge_result.is_ok());
+
+    (dir.clone(), dir_str, engine_state, stack)
+}
+
+#[allow(dead_code)]
+// match a list of suggestions with the expected values
+pub fn match_suggestions(expected: Vec<String>, suggestions: Vec<Suggestion>) {
+    expected.iter().zip(suggestions).for_each(|it| {
+        assert_eq!(it.0, &it.1.value);
+    });
+}
+
+#[allow(dead_code)]
+// append the separator to the converted path
+pub fn folder(path: PathBuf) -> String {
+    let mut converted_path = file(path);
+    converted_path.push(SEP);
+
+    converted_path
+}
+
+#[allow(dead_code)]
+// convert a given path to string
+pub fn file(path: PathBuf) -> String {
+    path.into_os_string().into_string().unwrap_or_default()
+}