Test: basic lazyfree unit test.

tests/test_helper.tcl

@@ -51,6 +51,7 @@ set ::all_tests {
     unit/bitops
     unit/memefficiency
     unit/hyperloglog
+    unit/lazyfree
 }
 # Index to the next test to run in the ::all_tests list.
 set ::next_test 0

tests/unit/lazyfree.tcl

@@ -0,0 +1,39 @@
+start_server {tags {"lazyfree"}} {
+    test "UNLINK can reclaim memory in background" {
+        set orig_mem [s used_memory]
+        set args {}
+        for {set i 0} {$i < 100000} {incr i} {
+            lappend args $i
+        }
+        r sadd myset {*}$args
+        assert {[r scard myset] == 100000}
+        set peak_mem [s used_memory]
+        assert {[r unlink myset] == 1}
+        assert {$peak_mem > $orig_mem+1000000}
+        wait_for_condition 50 100 {
+            [s used_memory] < $peak_mem &&
+            [s used_memory] < $orig_mem*2
+        } else {
+            fail "Memory is not reclaimed by UNLINK"
+        }
+    }
+
+    test "FLUSHDB ASYNC can reclaim memory in background" {
+        set orig_mem [s used_memory]
+        set args {}
+        for {set i 0} {$i < 100000} {incr i} {
+            lappend args $i
+        }
+        r sadd myset {*}$args
+        assert {[r scard myset] == 100000}
+        set peak_mem [s used_memory]
+        r flushdb async
+        assert {$peak_mem > $orig_mem+1000000}
+        wait_for_condition 50 100 {
+            [s used_memory] < $peak_mem &&
+            [s used_memory] < $orig_mem*2
+        } else {
+            fail "Memory is not reclaimed by FLUSHDB ASYNC"
+        }
+    }
+}