CG: test XGROUPREAD abilities.

tests/unit/type/stream-cgroups.tcl

@@ -8,4 +8,34 @@ start_server {
         catch {r XGROUP CREATE mystream mygroup $} err
         set err
     } {BUSYGROUP*}
+
+    test {XREADGROUP will return only new elements} {
+        r XADD mystream * a 1
+        r XADD mystream * b 2
+        # XREADGROUP should return only the new elements "a 1" "b 1"
+        # and not the element "foo bar" which was pre existing in the
+        # stream (see previous test)
+        set reply [
+            r XREADGROUP GROUP mygroup client-1 STREAMS mystream ">"
+        ]
+        assert {[llength [lindex $reply 0 1]] == 2}
+        lindex $reply 0 1 0 1
+    } {a 1}
+
+    test {XREADGROUP can read the history of the elements we own} {
+        # Add a few more elements
+        r XADD mystream * c 3
+        r XADD mystream * d 4
+        # Read a few elements using a different consumer name
+        set reply [
+            r XREADGROUP GROUP mygroup client-2 STREAMS mystream ">"
+        ]
+        assert {[llength [lindex $reply 0 1]] == 2}
+        assert {[lindex $reply 0 1 0 1] eq {c 3}}
+
+        set r1 [r XREADGROUP GROUP mygroup client-1 COUNT 10 STREAMS mystream 0]
+        set r2 [r XREADGROUP GROUP mygroup client-2 COUNT 10 STREAMS mystream 0]
+        assert {[lindex $r1 0 1 0 1] eq {a 1}}
+        assert {[lindex $r2 0 1 0 1] eq {c 3}}
+    }
 }