diff --git a/internal/asynqtest/asynqtest.go b/internal/asynqtest/asynqtest.go
index a3d1452..50e73ef 100644
--- a/internal/asynqtest/asynqtest.go
+++ b/internal/asynqtest/asynqtest.go
@@ -182,42 +182,42 @@ func FlushDB(tb testing.TB, r redis.UniversalClient) {
 func SeedPendingQueue(tb testing.TB, r redis.UniversalClient, msgs []*base.TaskMessage, qname string) {
 	tb.Helper()
 	r.SAdd(base.AllQueues, qname)
-	seedRedisList(tb, r, base.PendingKey(qname), msgs, "pending")
+	seedRedisList(tb, r, base.PendingKey(qname), msgs, base.TaskStatePending)
 }
 
 // SeedActiveQueue initializes the active queue with the given messages.
 func SeedActiveQueue(tb testing.TB, r redis.UniversalClient, msgs []*base.TaskMessage, qname string) {
 	tb.Helper()
 	r.SAdd(base.AllQueues, qname)
-	seedRedisList(tb, r, base.ActiveKey(qname), msgs, "active")
+	seedRedisList(tb, r, base.ActiveKey(qname), msgs, base.TaskStateActive)
 }
 
 // SeedScheduledQueue initializes the scheduled queue with the given messages.
 func SeedScheduledQueue(tb testing.TB, r redis.UniversalClient, entries []base.Z, qname string) {
 	tb.Helper()
 	r.SAdd(base.AllQueues, qname)
-	seedRedisZSet(tb, r, base.ScheduledKey(qname), entries, "scheduled")
+	seedRedisZSet(tb, r, base.ScheduledKey(qname), entries, base.TaskStateScheduled)
 }
 
 // SeedRetryQueue initializes the retry queue with the given messages.
 func SeedRetryQueue(tb testing.TB, r redis.UniversalClient, entries []base.Z, qname string) {
 	tb.Helper()
 	r.SAdd(base.AllQueues, qname)
-	seedRedisZSet(tb, r, base.RetryKey(qname), entries, "retry")
+	seedRedisZSet(tb, r, base.RetryKey(qname), entries, base.TaskStateRetry)
 }
 
 // SeedArchivedQueue initializes the archived queue with the given messages.
 func SeedArchivedQueue(tb testing.TB, r redis.UniversalClient, entries []base.Z, qname string) {
 	tb.Helper()
 	r.SAdd(base.AllQueues, qname)
-	seedRedisZSet(tb, r, base.ArchivedKey(qname), entries, "archived")
+	seedRedisZSet(tb, r, base.ArchivedKey(qname), entries, base.TaskStateArchived)
 }
 
 // SeedDeadlines initializes the deadlines set with the given entries.
 func SeedDeadlines(tb testing.TB, r redis.UniversalClient, entries []base.Z, qname string) {
 	tb.Helper()
 	r.SAdd(base.AllQueues, qname)
-	seedRedisZSet(tb, r, base.DeadlinesKey(qname), entries, "active")
+	seedRedisZSet(tb, r, base.DeadlinesKey(qname), entries, base.TaskStateActive)
 }
 
 // SeedAllPendingQueues initializes all of the specified queues with the given messages.
@@ -271,7 +271,7 @@ func SeedAllDeadlines(tb testing.TB, r redis.UniversalClient, deadlines map[stri
 }
 
 func seedRedisList(tb testing.TB, c redis.UniversalClient, key string,
-	msgs []*base.TaskMessage, state string) {
+	msgs []*base.TaskMessage, state base.TaskState) {
 	tb.Helper()
 	for _, msg := range msgs {
 		encoded := MustMarshal(tb, msg)
@@ -281,7 +281,7 @@ func seedRedisList(tb testing.TB, c redis.UniversalClient, key string,
 		key := base.TaskKey(msg.Queue, msg.ID.String())
 		data := map[string]interface{}{
 			"msg":      encoded,
-			"state":    state,
+			"state":    state.String(),
 			"timeout":  msg.Timeout,
 			"deadline": msg.Deadline,
 		}
@@ -292,7 +292,7 @@ func seedRedisList(tb testing.TB, c redis.UniversalClient, key string,
 }
 
 func seedRedisZSet(tb testing.TB, c redis.UniversalClient, key string,
-	items []base.Z, state string) {
+	items []base.Z, state base.TaskState) {
 	tb.Helper()
 	for _, item := range items {
 		msg := item.Message
@@ -304,7 +304,7 @@ func seedRedisZSet(tb testing.TB, c redis.UniversalClient, key string,
 		key := base.TaskKey(msg.Queue, msg.ID.String())
 		data := map[string]interface{}{
 			"msg":      encoded,
-			"state":    state,
+			"state":    state.String(),
 			"timeout":  msg.Timeout,
 			"deadline": msg.Deadline,
 		}
@@ -318,68 +318,68 @@ func seedRedisZSet(tb testing.TB, c redis.UniversalClient, key string,
 // It also asserts the state field of the task.
 func GetPendingMessages(tb testing.TB, r redis.UniversalClient, qname string) []*base.TaskMessage {
 	tb.Helper()
-	return getMessagesFromList(tb, r, qname, base.PendingKey, "pending")
+	return getMessagesFromList(tb, r, qname, base.PendingKey, base.TaskStatePending)
 }
 
 // GetActiveMessages returns all active messages in the given queue.
 // It also asserts the state field of the task.
 func GetActiveMessages(tb testing.TB, r redis.UniversalClient, qname string) []*base.TaskMessage {
 	tb.Helper()
-	return getMessagesFromList(tb, r, qname, base.ActiveKey, "active")
+	return getMessagesFromList(tb, r, qname, base.ActiveKey, base.TaskStateActive)
 }
 
 // GetScheduledMessages returns all scheduled task messages in the given queue.
 // It also asserts the state field of the task.
 func GetScheduledMessages(tb testing.TB, r redis.UniversalClient, qname string) []*base.TaskMessage {
 	tb.Helper()
-	return getMessagesFromZSet(tb, r, qname, base.ScheduledKey, "scheduled")
+	return getMessagesFromZSet(tb, r, qname, base.ScheduledKey, base.TaskStateScheduled)
 }
 
 // GetRetryMessages returns all retry messages in the given queue.
 // It also asserts the state field of the task.
 func GetRetryMessages(tb testing.TB, r redis.UniversalClient, qname string) []*base.TaskMessage {
 	tb.Helper()
-	return getMessagesFromZSet(tb, r, qname, base.RetryKey, "retry")
+	return getMessagesFromZSet(tb, r, qname, base.RetryKey, base.TaskStateRetry)
 }
 
 // GetArchivedMessages returns all archived messages in the given queue.
 // It also asserts the state field of the task.
 func GetArchivedMessages(tb testing.TB, r redis.UniversalClient, qname string) []*base.TaskMessage {
 	tb.Helper()
-	return getMessagesFromZSet(tb, r, qname, base.ArchivedKey, "archived")
+	return getMessagesFromZSet(tb, r, qname, base.ArchivedKey, base.TaskStateArchived)
 }
 
 // GetScheduledEntries returns all scheduled messages and its score in the given queue.
 // It also asserts the state field of the task.
 func GetScheduledEntries(tb testing.TB, r redis.UniversalClient, qname string) []base.Z {
 	tb.Helper()
-	return getMessagesFromZSetWithScores(tb, r, qname, base.ScheduledKey, "scheduled")
+	return getMessagesFromZSetWithScores(tb, r, qname, base.ScheduledKey, base.TaskStateScheduled)
 }
 
 // GetRetryEntries returns all retry messages and its score in the given queue.
 // It also asserts the state field of the task.
 func GetRetryEntries(tb testing.TB, r redis.UniversalClient, qname string) []base.Z {
 	tb.Helper()
-	return getMessagesFromZSetWithScores(tb, r, qname, base.RetryKey, "retry")
+	return getMessagesFromZSetWithScores(tb, r, qname, base.RetryKey, base.TaskStateRetry)
 }
 
 // GetArchivedEntries returns all archived messages and its score in the given queue.
 // It also asserts the state field of the task.
 func GetArchivedEntries(tb testing.TB, r redis.UniversalClient, qname string) []base.Z {
 	tb.Helper()
-	return getMessagesFromZSetWithScores(tb, r, qname, base.ArchivedKey, "archived")
+	return getMessagesFromZSetWithScores(tb, r, qname, base.ArchivedKey, base.TaskStateArchived)
 }
 
 // GetDeadlinesEntries returns all task messages and its score in the deadlines set for the given queue.
 // It also asserts the state field of the task.
 func GetDeadlinesEntries(tb testing.TB, r redis.UniversalClient, qname string) []base.Z {
 	tb.Helper()
-	return getMessagesFromZSetWithScores(tb, r, qname, base.DeadlinesKey, "active")
+	return getMessagesFromZSetWithScores(tb, r, qname, base.DeadlinesKey, base.TaskStateActive)
 }
 
 // Retrieves all messages stored under `keyFn(qname)` key in redis list.
 func getMessagesFromList(tb testing.TB, r redis.UniversalClient, qname string,
-	keyFn func(qname string) string, state string) []*base.TaskMessage {
+	keyFn func(qname string) string, state base.TaskState) []*base.TaskMessage {
 	tb.Helper()
 	ids := r.LRange(keyFn(qname), 0, -1).Val()
 	var msgs []*base.TaskMessage
@@ -387,8 +387,8 @@ func getMessagesFromList(tb testing.TB, r redis.UniversalClient, qname string,
 		taskKey := base.TaskKey(qname, id)
 		data := r.HGet(taskKey, "msg").Val()
 		msgs = append(msgs, MustUnmarshal(tb, data))
-		if gotState := r.HGet(taskKey, "state").Val(); gotState != state {
-			tb.Errorf("task (id=%q) is in %q state, want %q", id, gotState, state)
+		if gotState := r.HGet(taskKey, "state").Val(); gotState != state.String() {
+			tb.Errorf("task (id=%q) is in %q state, want %v", id, gotState, state)
 		}
 	}
 	return msgs
@@ -396,7 +396,7 @@ func getMessagesFromList(tb testing.TB, r redis.UniversalClient, qname string,
 
 // Retrieves all messages stored under `keyFn(qname)` key in redis zset (sorted-set).
 func getMessagesFromZSet(tb testing.TB, r redis.UniversalClient, qname string,
-	keyFn func(qname string) string, state string) []*base.TaskMessage {
+	keyFn func(qname string) string, state base.TaskState) []*base.TaskMessage {
 	tb.Helper()
 	ids := r.ZRange(keyFn(qname), 0, -1).Val()
 	var msgs []*base.TaskMessage
@@ -404,8 +404,8 @@ func getMessagesFromZSet(tb testing.TB, r redis.UniversalClient, qname string,
 		taskKey := base.TaskKey(qname, id)
 		msg := r.HGet(taskKey, "msg").Val()
 		msgs = append(msgs, MustUnmarshal(tb, msg))
-		if gotState := r.HGet(taskKey, "state").Val(); gotState != state {
-			tb.Errorf("task (id=%q) is in %q state, want %q", id, gotState, state)
+		if gotState := r.HGet(taskKey, "state").Val(); gotState != state.String() {
+			tb.Errorf("task (id=%q) is in %q state, want %v", id, gotState, state)
 		}
 	}
 	return msgs
@@ -413,7 +413,7 @@ func getMessagesFromZSet(tb testing.TB, r redis.UniversalClient, qname string,
 
 // Retrieves all messages along with their scores stored under `keyFn(qname)` key in redis zset (sorted-set).
 func getMessagesFromZSetWithScores(tb testing.TB, r redis.UniversalClient,
-	qname string, keyFn func(qname string) string, state string) []base.Z {
+	qname string, keyFn func(qname string) string, state base.TaskState) []base.Z {
 	tb.Helper()
 	zs := r.ZRangeWithScores(keyFn(qname), 0, -1).Val()
 	var res []base.Z
@@ -422,8 +422,8 @@ func getMessagesFromZSetWithScores(tb testing.TB, r redis.UniversalClient,
 		taskKey := base.TaskKey(qname, taskID)
 		msg := r.HGet(taskKey, "msg").Val()
 		res = append(res, base.Z{Message: MustUnmarshal(tb, msg), Score: int64(z.Score)})
-		if gotState := r.HGet(taskKey, "state").Val(); gotState != state {
-			tb.Errorf("task (id=%q) is in %q state, want %q", taskID, gotState, state)
+		if gotState := r.HGet(taskKey, "state").Val(); gotState != state.String() {
+			tb.Errorf("task (id=%q) is in %q state, want %v", taskID, gotState, state)
 		}
 	}
 	return res
diff --git a/internal/base/base.go b/internal/base/base.go
index db9c145..bb31b7b 100644
--- a/internal/base/base.go
+++ b/internal/base/base.go
@@ -36,6 +36,33 @@ const (
 	CancelChannel = "asynq:cancel"     // PubSub channel
 )
 
+// TaskState denotes the state of a task.
+type TaskState int
+
+const (
+	TaskStateActive TaskState = iota + 1
+	TaskStatePending
+	TaskStateScheduled
+	TaskStateRetry
+	TaskStateArchived
+)
+
+func (s TaskState) String() string {
+	switch s {
+	case TaskStateActive:
+		return "active"
+	case TaskStatePending:
+		return "pending"
+	case TaskStateScheduled:
+		return "scheduled"
+	case TaskStateRetry:
+		return "retry"
+	case TaskStateArchived:
+		return "archived"
+	}
+	panic(fmt.Sprintf("internal error: unknown task state %d", s))
+}
+
 // ValidateQueueName validates a given qname to be used as a queue name.
 // Returns nil if valid, otherwise returns non-nil error.
 func ValidateQueueName(qname string) error {