Added 048 acceptance test

examples/acceptance_tests/048/lib/tests.ak

@@ -0,0 +1,9 @@
+pub fn when_tuple(a: (Int, Int)) -> Int {
+  when a is {
+    (a, b) -> a
+  }
+}
+
+test when_tuple_1() {
+  when_tuple((4, 1)) == 4
+}