Autocomplete tests

src/error.rs

@@ -200,6 +200,10 @@ Is there a permissions issue? Here's the underlaying error:
 letters, numbers, dots, dashes and underscores are allowed.")]
     InvalidCustomFormatter(String),
 
+    #[error("The specified name for a autocompleted formatter \"{0}\" is not valid. Only ascii
+letters, numbers, dots, dashes and underscores are allowed.")]
+    InvalidAutocompleteFormatter(String),
+
     #[error("You have specified a custom formatter \"{0}\" but your config file doesn't say
 where to look for it.
 

src/formatters.rs

@@ -74,3 +74,47 @@ impl FromStr for Formatter {
         })
     }
 }
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+
+    fn autocomplete(s: &str) -> error::Result<Formatter> {
+        let formatters = vec!["text", "csv", "json", "ids", "ical", "chart"];
+        if s.len() > 1 {
+            for formatter in formatters {
+                if formatter.contains(s) {
+                    return Formatter::from_str(formatter)
+                }
+            }
+        }
+        Err(error::Error::InvalidAutocompleteFormatter(s.to_string()))
+    }
+
+    #[test]
+    fn valid_autocomplete_starts_with() {
+        let format = autocomplete("tex");
+        assert!(format.is_ok());
+    }
+
+    #[test]
+    fn valid_autocomplete_contains() {
+        let format = autocomplete("sv");
+        assert!(format.is_ok());
+    }
+
+    #[test]
+    fn invalid_autocomplete_to_short() {
+        let format = autocomplete("s");
+        assert!(format.is_err());
+    }
+
+    #[test]
+    fn invalid_autocomplete_does_not_contains() {
+        let format = autocomplete("fail");
+        assert!(format.is_err());
+    }
+
+    // TODO: autocomplete for custom formatter
+}