Tracking: first set of tests for the feature.

tests/unit/tracking.tcl

+start_server {tags {"tracking"}} {
+    # Create a deferred client we'll use to redirect invalidation
+    # messages to.
+    set rd1 [redis_deferring_client]
+    $rd1 client id
+    set redir [$rd1 read]
+    $rd1 subscribe __redis__:invalidate
+    $rd1 read ; # Consume the SUBSCRIBE reply.
+
+    test {Clients are able to enable tracking and redirect it} {
+        r CLIENT TRACKING on REDIRECT $redir
+    } {*OK}
+
+    test {The other connection is able to get invalidations} {
+        r SET a 1
+        r GET a
+        r INCR a
+        r INCR b ; # This key should not be notified, since it wasn't fetched.
+        set keys [lindex [$rd1 read] 2]
+        assert {[llength $keys] == 1}
+        assert {[lindex $keys 0] eq {a}}
+    }
+
+    test {The client is now able to disable tracking} {
+        # Make sure to add a few more keys in the tracking list
+        # so that we can check for leaks, as a side effect.
+        r MGET a b c d e f g
+        r CLIENT TRACKING off
+    }
+
+    test {Clients can enable the BCAST mode with the empty prefix} {
+        r CLIENT TRACKING on BCAST REDIRECT $redir
+    } {*OK*}
+
+    test {The connection gets invalidation messages about all the keys} {
+        r MSET a 1 b 2 c 3
+        set keys [lsort [lindex [$rd1 read] 2]]
+        assert {$keys eq {a b c}}
+    }
+
+    test {Clients can enable the BCAST mode with prefixes} {
+        r CLIENT TRACKING off
+        r CLIENT TRACKING on BCAST REDIRECT $redir PREFIX a: PREFIX b:
+        r MULTI
+        r INCR a:1
+        r INCR a:2
+        r INCR b:1
+        r INCR b:2
+        r EXEC
+        # Because of the internals, we know we are going to receive
+        # two separated notifications for the two different prefixes.
+        set keys1 [lsort [lindex [$rd1 read] 2]]
+        set keys2 [lsort [lindex [$rd1 read] 2]]
+        set keys [lsort [list {*}$keys1 {*}$keys2]]
+        assert {$keys eq {a:1 a:2 b:1 b:2}}
+    }
+    
+    test {Adding prefixes to BCAST mode works} {
+        r CLIENT TRACKING on BCAST REDIRECT $redir PREFIX c:
+        r INCR c:1234
+        set keys [lsort [lindex [$rd1 read] 2]]
+        assert {$keys eq {c:1234}}
+    }
+
+    $rd1 close
+}