diff --git a/src/action-queue.lua b/src/action-queue.lua
index efe6956..f9e2677 100644
--- a/src/action-queue.lua
+++ b/src/action-queue.lua
@@ -1,5 +1,6 @@
+---@class ActionQueue
+---@field queue table<any, { coroutine: thread, expireTimeMs: number }>
 actionQueue = {
-    ---@type table<any, { coroutine: thread, expireTimeMs: number }>
     queue = {},
 }
 
@@ -52,3 +53,8 @@ function actionQueue:runWaiting(deltaSeconds)
         end
     end
 end
+
+-- luacheck: ignore
+if not playdate or playdate.TEST_MODE then
+    return actionQueue
+end
diff --git a/src/test/mocks.lua b/src/test/mocks.lua
index 1fca7ad..8ec6658 100644
--- a/src/test/mocks.lua
+++ b/src/test/mocks.lua
@@ -1,7 +1,16 @@
 utils = require("utils")
 
+local currentTimeMs = 0
+
 local mockPlaydate = {
     TEST_MODE = true,
+    skipMs = function(skip)
+        currentTimeMs = currentTimeMs + skip
+    end,
+    getCurrentTimeMilliseconds = function()
+        currentTimeMs = currentTimeMs + 1
+        return currentTimeMs
+    end,
     timer = {
         new = function(_, callback)
             return {
diff --git a/src/test/testActionQueue.lua b/src/test/testActionQueue.lua
new file mode 100644
index 0000000..433a2f2
--- /dev/null
+++ b/src/test/testActionQueue.lua
@@ -0,0 +1,87 @@
+require("test/setup")
+require("action-queue")
+
+function testActionQueueRunsToCompletion()
+    actionQueue.queue = {}
+    local invokeTotalSec = 0
+    local hasYielded = false
+    actionQueue:upsert("testAction", 9999999999, function(delta)
+        while invokeTotalSec < 5 do
+            invokeTotalSec = invokeTotalSec + delta
+            hasYielded = true
+            coroutine.yield()
+        end
+    end)
+    luaunit.assertIsFalse(hasYielded, "Should not have been invoked yet.")
+    for _ = 1, 10 do
+        actionQueue:runWaiting(1)
+        luaunit.assertIsTrue(hasYielded, "Should have been invoked.")
+    end
+    luaunit.assertEquals(5, invokeTotalSec, "Should have run five times and stopped itself")
+end
+
+function testActionQueueExpiration()
+    actionQueue.queue = {}
+    local yieldCount = 0
+    actionQueue:upsert("testAction", 2000, function(delta)
+        while true do
+            yieldCount = yieldCount + 1
+            coroutine.yield()
+        end
+    end)
+
+    local skipSec = 60
+    playdate.skipMs(60 * 1000)
+    actionQueue:runWaiting(skipSec)
+    luaunit.assertEquals(1, yieldCount, "Should always be invoked at least once")
+
+    playdate.skipMs(1000)
+    actionQueue:runWaiting(1)
+    luaunit.assertEquals(1, yieldCount, "Should not be invoked again after expiry")
+end
+
+function testDuplicateUpsertsShouldOnlyRunOnce()
+    actionQueue.queue = {}
+    local yieldCount = 0
+    local yieldId
+    local action = function(id)
+        return function()
+            while true do
+                yieldCount = yieldCount + 1
+                yieldId = id
+                coroutine.yield()
+            end
+        end
+    end
+
+    for i = 1, 10 do
+        actionQueue:upsert("testAction", 9999999999, action(i))
+    end
+    actionQueue:runWaiting(1)
+    luaunit.assertEquals(1, yieldCount, "Duplicate upserts should result in only one invocation.")
+    luaunit.assertEquals(10, yieldId, "Most recent upsert should take precedence.")
+end
+
+function testNewOnlyActionsShouldNotReplaceExistingActions()
+    actionQueue.queue = {}
+    local yieldCount = 0
+    local yieldId
+    local action = function(id)
+        return function()
+            while true do
+                yieldCount = yieldCount + 1
+                yieldId = id
+                coroutine.yield()
+            end
+        end
+    end
+
+    for i = 1, 10 do
+        actionQueue:newOnly("testAction", 9999999999, action(i))
+    end
+    actionQueue:runWaiting(1)
+    luaunit.assertEquals(1, yieldCount, "Duplicate newOnly should result in only one invocation.")
+    luaunit.assertEquals(1, yieldId, "The first newOnly should take precedence.")
+end
+
+os.exit(luaunit.LuaUnit.run())