Add tests for Supply.head

Author: lizmat

S17-supply/head.t

@@ -0,0 +1,18 @@
+use v6;
+use lib 't/spec/packages';
+
+use Test;
+use Test::Tap;
+
+plan 8;
+
+dies-ok { Supply.head }, 'can not be called as a class method';
+dies-ok { Supply.new.head("foo") }, 'cannot have "foo" head';
+
+for ThreadPoolScheduler.new, CurrentThreadScheduler -> $*SCHEDULER {
+    diag "**** scheduling with {$*SCHEDULER.WHAT.perl}";
+
+    tap-ok Supply.from-list(1..10).head, [1,], "head without argument works";
+    tap-ok Supply.from-list(1..10).head(5), [1..5], "head five works";
+    tap-ok Supply.from-list(1..10).head(15), [1..10], "head 15 works";
+}