tests ~ reorganize tests

tests/by-util/test_link.rs

@@ -0,0 +1,41 @@
+use crate::common::util::*;
+
+#[test]
+fn test_link_existing_file() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let file = "test_link_existing_file";
+    let link = "test_link_existing_file_link";
+
+    at.touch(file);
+    at.write(file, "foobar");
+    assert!(at.file_exists(file));
+
+    ucmd.args(&[file, link]).succeeds().no_stderr();
+    assert!(at.file_exists(file));
+    assert!(at.file_exists(link));
+    assert_eq!(at.read(file), at.read(link));
+}
+
+#[test]
+fn test_link_no_circular() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let link = "test_link_no_circular";
+
+    ucmd.args(&[link, link])
+        .fails()
+        .stderr_is("link: error: No such file or directory (os error 2)\n");
+    assert!(!at.file_exists(link));
+}
+
+#[test]
+fn test_link_nonexistent_file() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let file = "test_link_nonexistent_file";
+    let link = "test_link_nonexistent_file_link";
+
+    ucmd.args(&[file, link])
+        .fails()
+        .stderr_is("link: error: No such file or directory (os error 2)\n");
+    assert!(!at.file_exists(file));
+    assert!(!at.file_exists(link));
+}