stdlib: add an automatic loading of "prelude" commands (#8627)

src/tests/test_stdlib.rs

@@ -0,0 +1,35 @@
+use crate::tests::{fail_test, run_test, TestResult};
+
+#[test]
+fn library_loaded() -> TestResult {
+    run_test(
+        "help std | lines | first 1 | to text",
+        "std.nu, `used` to load all standard library components",
+    )
+}
+
+#[test]
+fn prelude_loaded() -> TestResult {
+    run_test(
+        "help assert | lines | first 1 | to text",
+        "Universal assert command",
+    )
+}
+
+#[test]
+fn prelude_run() -> TestResult {
+    run_test("assert true; print 'it works'", "it works")
+}
+
+#[test]
+fn not_loaded() -> TestResult {
+    fail_test("help log info", "")
+}
+
+#[test]
+fn use_command() -> TestResult {
+    run_test(
+        "use std 'log info'; log info 'this is some information'",
+        "",
+    )
+}