make the --length argument require a value

2 files changed, 11 insertions, 3 deletions

diff --git a/b3sum/src/main.rs b/b3sum/src/main.rs
index 3fc074c..cb2bb15 100644
--- a/b3sum/src/main.rs
+++ b/b3sum/src/main.rs
@@ -21,8 +21,7 @@ fn clap_parse_argv() -> clap::ArgMatches<'static> {
                 .short("l")
                 .takes_value(true)
                 .value_name("LEN")
-                .default_value("32")
-                .help("The number of output bytes, prior to hex encoding"),
+                .help("The number of output bytes, prior to hex encoding (default 32)"),
         )
         .arg(
             Arg::with_name(KEYED_ARG)
@@ -156,7 +155,7 @@ fn main() -> Result<()> {
     let args = clap_parse_argv();
     let len: u64 = args
         .value_of(LENGTH_ARG)
-        .unwrap()
+        .unwrap_or("32")
         .parse()
         .context("Failed to parse length.")?;
     let base_hasher = if args.is_present(KEYED_ARG) {
diff --git a/b3sum/tests/test.rs b/b3sum/tests/test.rs
index 8f2e623..92e1c4c 100644
--- a/b3sum/tests/test.rs
+++ b/b3sum/tests/test.rs
@@ -84,3 +84,12 @@ fn test_derive_key() {
         .unwrap();
     assert_eq!(&*expected, &*output);
 }
+
+#[test]
+fn test_length_without_value_is_an_error() {
+    let result = cmd!(b3sum_exe(), "--length")
+        .stdin_bytes("foo")
+        .stderr_capture()
+        .run();
+    assert!(result.is_err());
+}