From 5dd6abb38fa9488f42aacb4d8963a1c1b42ec08a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A1s=20B=20Nagy?=
 <20251272+BNAndras@users.noreply.github.com>
Date: Thu, 16 May 2024 09:51:34 -0700
Subject: [PATCH] Sync hamming tests and update stub (#243)

---
 exercises/practice/hamming/.meta/example.lfe  | 13 +++++---
 exercises/practice/hamming/src/hamming.lfe    |  4 +++
 .../practice/hamming/test/hamming-tests.lfe   | 31 ++++++++++++-------
 3 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/exercises/practice/hamming/.meta/example.lfe b/exercises/practice/hamming/.meta/example.lfe
index 80675e8b..87aa711d 100644
--- a/exercises/practice/hamming/.meta/example.lfe
+++ b/exercises/practice/hamming/.meta/example.lfe
@@ -1,8 +1,11 @@
 (defmodule hamming
   (export (distance 2)))
 
-(defun distance (strand-x strand-y)
-  (lists:sum
-    (lists:zipwith
-      (lambda (x y) (if (=:= x y) 0 1))
-      strand-x strand-y)))
+(defun distance (strand1 strand2)
+  (if (not (== (length strand1) (length strand2)))
+    (error "strands must have the same length")
+    (lists:sum
+      (lists:zipwith
+        (lambda (a b) (if (=:= a b) 0 1))
+        strand1
+        strand2))))
diff --git a/exercises/practice/hamming/src/hamming.lfe b/exercises/practice/hamming/src/hamming.lfe
index e69de29b..a3f0629e 100644
--- a/exercises/practice/hamming/src/hamming.lfe
+++ b/exercises/practice/hamming/src/hamming.lfe
@@ -0,0 +1,4 @@
+(defmodule hamming
+  (export (distance 2)))
+
+ ; Please implement the distance function.
diff --git a/exercises/practice/hamming/test/hamming-tests.lfe b/exercises/practice/hamming/test/hamming-tests.lfe
index 748480f1..30d65f10 100644
--- a/exercises/practice/hamming/test/hamming-tests.lfe
+++ b/exercises/practice/hamming/test/hamming-tests.lfe
@@ -4,20 +4,29 @@
 
 (include-lib "ltest/include/ltest-macros.lfe")
 
-(deftest empty
+(deftest empty-strands
   (is-equal 0 (hamming:distance "" "")))
 
-(deftest equal
-  (is-equal 0 (hamming:distance "GAGCCTACTAACGGGAT" "GAGCCTACTAACGGGAT")))
+(deftest single-letter-identical-strands
+  (is-equal 0 (hamming:distance "A" "A")))
 
-(deftest all-different
-  (is-equal 17 (hamming:distance "GAGCCTACTAACGGGAT" "FFFFFFFFFFFFFFFFF")))
+(deftest single-letter-different-strands
+  (is-equal 1 (hamming:distance "G" "T")))
 
-(deftest ends-different
-  (is-equal 2 (hamming:distance "GAGCCTACTAACGGGAT" "TAGCCTACTAACGGGAG")))
+(deftest long-identical-strands
+  (is-equal 0 (hamming:distance "GGACTGAAATCTG" "GGACTGAAATCTG")))
 
-(deftest middle-different
-  (is-equal 1 (hamming:distance "GAGCCTACTAACGGGAT" "GAGCCTACCAACGGGAT")))
+(deftest long-different-strands
+  (is-equal 9 (hamming:distance "GGACGGATTCTG" "AGGACGGATTCT")))
 
-(deftest some-differences
-  (is-equal 6 (hamming:distance "GAGCCTACTAACGGGAT" "GAACCTCCCAAGGGATT")))
+(deftest disallow-first-strand-longer
+  (is-error (hamming:distance "AATG" "AAA")))
+
+(deftest disallow-second-strand-longer
+  (is-error (hamming:distance "ATA" "AGTG")))
+
+(deftest disallow-empty-first-strand
+  (is-error (hamming:distance "" "G")))
+
+(deftest disallow-empty-second-strand
+  (is-error (hamming:distance "G" "")))