diff --git a/.gitignore b/.gitignore
index fa36f444f..3313fb28c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,6 +24,7 @@ koreader-*.click
 l10n/*
 !l10n/Makefile
 !l10n/README.md
+i18n
 
 /.cproject
 /.project
diff --git a/spec/unit/uimanager_bench.lua b/spec/unit/uimanager_bench.lua
new file mode 100644
index 000000000..2eafcd64a
--- /dev/null
+++ b/spec/unit/uimanager_bench.lua
@@ -0,0 +1,49 @@
+require("commonrequire")
+local util = require("ffi/util")
+local UIManager = require("ui/uimanager")
+
+local noop = function() end
+
+describe("UIManager checkTasks benchmark", function()
+    local now = { util.gettime() }
+    UIManager:quit()
+    UIManager._task_queue = {}
+
+    for i=1,1000000 do
+        table.insert(
+            UIManager._task_queue,
+            { time = { now[1] + 10000+i, now[2] }, action = noop }
+        )
+    end
+
+    -- for i=1,1000 do
+        wait_until, now = UIManager:_checkTasks()
+    -- end
+end)
+
+describe("UIManager schedule benchmark", function()
+    local now = { util.gettime() }
+    UIManager:quit()
+    UIManager._task_queue = {}
+    for i=1,100000 do
+        UIManager:schedule({ now[1] + i, now[2] }, noop)
+    end
+end)
+
+describe("UIManager unschedule benchmark", function()
+    local now = { util.gettime() }
+    UIManager:quit()
+    UIManager._task_queue = {}
+
+    for i=1,1000 do
+        table.insert(
+            UIManager._task_queue,
+            { time = { now[1] + 10000+i, now[2] }, action = 'a' }
+        )
+    end
+
+    for i=1,1000 do
+        UIManager:schedule(now, noop)
+        UIManager:unschedule(noop)
+    end
+end)
diff --git a/spec/unit/uimanager_spec.lua b/spec/unit/uimanager_spec.lua
new file mode 100644
index 000000000..b7b170bcc
--- /dev/null
+++ b/spec/unit/uimanager_spec.lua
@@ -0,0 +1,137 @@
+require("commonrequire")
+local util = require("ffi/util")
+local UIManager = require("ui/uimanager")
+local DEBUG = require("dbg")
+DEBUG:turnOn()
+
+describe("UIManager spec", function()
+    local noop = function() end
+
+    it("should consume due tasks", function()
+        local now = { util.gettime() }
+        local future = { now[1] + 60000, now[2] }
+        local future2 = {future[1] + 5, future[2]}
+        UIManager:quit()
+        UIManager._task_queue = {
+            { time = {now[1] - 10, now[2] }, action = noop },
+            { time = {now[1], now[2] - 5 }, action = noop },
+            { time = now, action = noop },
+            { time = future, action = noop },
+            { time = future2, action = noop },
+        }
+        UIManager:_checkTasks()
+        assert.are.same(#UIManager._task_queue, 2)
+        assert.are.same(UIManager._task_queue[1].time, future)
+        assert.are.same(UIManager._task_queue[2].time, future2)
+    end)
+
+    it("should calcualte wait_until properly in checkTasks routine", function()
+        local now = { util.gettime() }
+        local future = { now[1] + 60000, now[2] }
+        UIManager:quit()
+        UIManager._task_queue = {
+            { time = {now[1] - 10, now[2] }, action = noop },
+            { time = {now[1], now[2] - 5 }, action = noop },
+            { time = now, action = noop },
+            { time = future, action = noop },
+            { time = {future[1] + 5, future[2]}, action = noop },
+        }
+        wait_until, now = UIManager:_checkTasks()
+        assert.are.same(wait_until, future)
+    end)
+
+    it("should return nil wait_until properly in checkTasks routine", function()
+        local now = { util.gettime() }
+        UIManager:quit()
+        UIManager._task_queue = {
+            { time = {now[1] - 10, now[2] }, action = noop },
+            { time = {now[1], now[2] - 5 }, action = noop },
+            { time = now, action = noop },
+        }
+        wait_until, now = UIManager:_checkTasks()
+        assert.are.same(wait_until, nil)
+    end)
+
+    it("should insert new task properly in empty task queue", function()
+        local now = { util.gettime() }
+        UIManager:quit()
+        UIManager._task_queue = {}
+        assert.are.same(0, #UIManager._task_queue)
+        UIManager:scheduleIn(50, 'foo')
+        assert.are.same(1, #UIManager._task_queue)
+        assert.are.same(UIManager._task_queue[1].action, 'foo')
+    end)
+
+    it("should insert new task properly in single task queue", function()
+        local now = { util.gettime() }
+        local future = { now[1]+10000, now[2] }
+        UIManager:quit()
+        UIManager._task_queue = {
+            { time = future, action = '1' },
+        }
+        assert.are.same(1, #UIManager._task_queue)
+        UIManager:scheduleIn(150, 'quz')
+        assert.are.same(2, #UIManager._task_queue)
+        assert.are.same(UIManager._task_queue[1].action, 'quz')
+
+        UIManager:quit()
+        UIManager._task_queue = {
+            { time = now, action = '1' },
+        }
+        assert.are.same(1, #UIManager._task_queue)
+        UIManager:scheduleIn(150, 'foo')
+        assert.are.same(2, #UIManager._task_queue)
+        assert.are.same(UIManager._task_queue[2].action, 'foo')
+        UIManager:scheduleIn(155, 'bar')
+        assert.are.same(3, #UIManager._task_queue)
+        assert.are.same(UIManager._task_queue[3].action, 'bar')
+    end)
+
+    it("should insert new task in ascendant order", function()
+        local now = { util.gettime() }
+        local noop1 = function() end
+        UIManager:quit()
+        UIManager._task_queue = {
+            { time = {now[1] - 10, now[2] }, action = '1' },
+            { time = {now[1], now[2] - 5 }, action = '2' },
+            { time = now, action = '3' },
+        }
+        -- insert into the tail slot
+        UIManager:scheduleIn(10, 'foo')
+        assert.are.same('foo', UIManager._task_queue[4].action)
+        -- insert into the second slot
+        UIManager:schedule({now[1]-5, now[2]}, 'bar')
+        assert.are.same('bar', UIManager._task_queue[2].action)
+        -- insert into the head slot
+        UIManager:schedule({now[1]-15, now[2]}, 'baz')
+        assert.are.same('baz', UIManager._task_queue[1].action)
+        -- insert into the last second slot
+        UIManager:scheduleIn(5, 'qux')
+        assert.are.same('qux', UIManager._task_queue[6].action)
+        -- insert into the middle slot
+        UIManager:schedule({now[1], now[2]-1}, 'quux')
+        assert.are.same('quux', UIManager._task_queue[5].action)
+    end)
+
+    it("should not have race between unschedule and _checkTasks", function()
+        local now = { util.gettime() }
+        local run_count = 0
+        local task_to_remove = function()
+            run_count = run_count + 1
+        end
+        UIManager:quit()
+        UIManager._task_queue = {
+            { time = { now[1], now[2]-5 }, action = task_to_remove },
+            {
+                time = { now[1]-10, now[2] },
+                action = function()
+                    run_count = run_count + 1
+                    UIManager:unschedule(task_to_remove)
+                end
+            },
+            { time = now, action = task_to_remove },
+        }
+        UIManager:_checkTasks()
+        assert.are.same(run_count, 2)
+    end)
+end)