Add test to check number of files flag

tests/tests.rs

@@ -368,3 +368,20 @@ pub fn test_hidden_flag() {
     let output = str::from_utf8(&output).unwrap();
     assert!(!output.contains(".hidden_file"));
 }
+
+#[test]
+pub fn test_number_of_files() {
+    // Check we can see the hidden file normally
+    let mut cmd = Command::cargo_bin("dust").unwrap();
+    let output = cmd
+        .arg("-c")
+        .arg("-f")
+        .arg("tests/test_dir")
+        .unwrap()
+        .stdout;
+    let output = str::from_utf8(&output).unwrap();
+    assert!(output.contains("1     ┌── hello_file"));
+    assert!(output.contains("1     ├── a_file "));
+    assert!(output.contains("3   ┌─┴ many"));
+    assert!(output.contains("4 ┌─┴ test_dir"));
+}