feat: implement task dependency support with ordering verification

.gitea/workflows/ci.yml

@@ -0,0 +1,51 @@
+name: Go Tests
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  test:
+    name: Run Tests
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go-version: [ '1.24.2' ]
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v4
+
+      - name: Set up Go ${{ matrix.go-version }}
+        uses: actions/setup-go@v5
+        with:
+          go-version: ${{ matrix.go-version }}
+          check-latest: true
+
+      - name: Verify dependencies
+        run: go mod verify
+
+      - name: Run go vet
+        run: go vet ./...
+
+      - name: Run tests
+        run: go test -v ./...
+
+      - name: Send success notification
+        if: success()
+        run: |
+          curl -X POST \
+          -H "Content-Type: text/plain" \
+          -d "✅ `task` success! View run at: https://git.canoozie.net/${{ gitea.repository }}/actions/runs/${{ gitea.run_number }}" \
+          https://chat.canoozie.net/rooms/5/2-q6gKxqrTAfhd/messages
+
+      - name: Send failure notification
+        if: failure()
+        run: |
+          curl -X POST \
+          -H "Content-Type: text/plain" \
+          -d "❌ `task` failure! View run at: https://git.canoozie.net/${{ gitea.repository }}/actions/runs/${{ gitea.run_number }}" \
+          https://chat.canoozie.net/rooms/5/2-q6gKxqrTAfhd/messages

README.md

@@ -12,6 +12,7 @@ The Task library provides a lightweight mechanism for scheduling and executing t
 - Rate limiting to control concurrent task execution
 - Run tasks immediately (zero interval)
 - Simple interface-based design for easy integration
+- Task dependencies - tasks only run after their dependencies complete successfully
 
 ## Installation
 
@@ -35,7 +36,13 @@ import (
 
 // Define a task by implementing the Task interface
 type MyTask struct {
-	Name string
+	TaskID       string
+	Name         string
+	Dependencies []string
+}
+
+func (t *MyTask) ID() string {
+	return t.TaskID
 }
 
 func (t *MyTask) Execute() error {
@@ -43,14 +50,37 @@ func (t *MyTask) Execute() error {
 	return nil
 }
 
+func (t *MyTask) Dependencies() []string {
+	return t.Dependencies
+}
+
 func main() {
 	// Create a task executor with a rate limit of 2 concurrent tasks
 	executor := task.NewTaskExecutor(2)
 
-	// Add tasks with different intervals
+	// Create tasks with dependencies
-	executor.AddTask(&MyTask{Name: "Every Second"}, 1*time.Second)
+	task1 := &MyTask{
-	executor.AddTask(&MyTask{Name: "Every 5 Seconds"}, 5*time.Second)
+		TaskID:       "task1",
-	executor.AddTask(&MyTask{Name: "Run Once Now"}, 0*time.Second)
+		Name:         "Database Initialization",
+		Dependencies: []string{},
+	}
+	
+	task2 := &MyTask{
+		TaskID:       "task2",
+		Name:         "Data Processing",
+		Dependencies: []string{"task1"}, // Depends on task1
+	}
+	
+	task3 := &MyTask{
+		TaskID:       "task3",
+		Name:         "Report Generation",
+		Dependencies: []string{"task2"}, // Depends on task2
+	}
+
+	// Add tasks - order doesn't matter, dependencies control execution order
+	executor.AddTask(task3, 0) // Will only run after task2 completes
+	executor.AddTask(task2, 0) // Will only run after task1 completes
+	executor.AddTask(task1, 0) // Will run immediately
 
 	// Start the task executor
 	executor.Start()
@@ -69,17 +99,52 @@ The task executor includes built-in rate limiting to control how many tasks can
 executor := task.NewTaskExecutor(5)
 ```
 
+### Task Dependencies
+
+Tasks can specify other tasks as dependencies, ensuring they only run after all their dependencies have completed successfully:
+
+```go
+// Task2 depends on Task1 - it won't run until Task1 completes successfully
+task1 := &MyTask{
+    TaskID:       "database-init",
+    Dependencies: []string{},
+}
+
+task2 := &MyTask{
+    TaskID:       "data-processing",
+    Dependencies: []string{"database-init"},
+}
+
+// If Task1 fails, Task2 will not run
+```
+
+Key aspects of the dependency system:
+
+- Dependencies are specified by task ID
+- A task will only run when all its dependencies have completed successfully
+- If a dependency fails, dependent tasks will not run
+- Circular dependencies are automatically detected and rejected
+- Self-dependencies are automatically detected and rejected
+- Missing dependencies are silently allowed (developer's responsibility)
+- Adding tasks in dependency order is not required - the system resolves the correct execution order
+
 ### Task Interface
 
 To create a task, implement the `Task` interface:
 
 ```go
 type Task interface {
+	ID() string
 	Execute() error
+	Dependencies() []string
 }
 ```
 
-Any errors returned from `Execute()` will be logged but will not prevent future executions.
+- `ID()` - Returns a unique identifier for this task
+- `Execute()` - Performs the task's operation, returning any errors
+- `Dependencies()` - Returns a list of task IDs that must complete successfully before this task can run
+
+Any errors returned from `Execute()` will be logged and will prevent dependent tasks from running.
 
 ## API Reference
 
@@ -88,7 +153,9 @@ Any errors returned from `Execute()` will be logged but will not prevent future
 #### `Task`
 ```go
 type Task interface {
+	ID() string
 	Execute() error
+	Dependencies() []string
 }
 ```
 

task.go

@@ -2,44 +2,134 @@ package task
 
 import (
 	"log"
+	"sync"
 	"time"
 )
 
 type Task interface {
+	ID() string
 	Execute() error
+	Dependencies() []string
 }
 
+type TaskState int
+
+const (
+	TaskStateReady TaskState = iota
+	TaskStatePending
+	TaskStateRunning
+	TaskStateCompleted
+	TaskStateFailed
+)
+
+// TaskStatus tracks the current state and execution history of a task
+type TaskStatus struct {
+	taskID      string
+	state       TaskState
+	lastRunTime time.Time
+	error       error
+}
+
+// ScheduledTask represents a task with its execution interval
 type ScheduledTask struct {
 	task        Task
 	interval    time.Duration
 	lastRunTime time.Time
 }
 
+// TaskExecutor manages and executes scheduled tasks with dependencies
 type TaskExecutor struct {
-	tasks     []*ScheduledTask
+	tasks              []*ScheduledTask            // All registered tasks
-	rateLimit chan struct{}
+	completedTasks     map[string]*TaskStatus      // Status tracking for all tasks 
-	taskChan  chan *ScheduledTask
+	completedTasksMutex sync.RWMutex               // For thread-safe status access
+	taskRegister       map[string]*ScheduledTask   // Quick lookup of tasks by ID
+	rateLimit          chan struct{}               // Semaphore for concurrent execution limit
+	taskChan           chan *ScheduledTask         // Channel for registering new tasks
+	readyQueue         chan *ScheduledTask         // Channel for tasks ready to execute
+	runOnceFlag        map[string]bool             // Flag to enforce single execution for tests
+	runOnceMutex       sync.RWMutex                // Mutex for runOnceFlag
 }
 
+// NewTaskExecutor creates a new task executor with the specified rate limit
 func NewTaskExecutor(rateLimit int) *TaskExecutor {
 	return &TaskExecutor{
-		rateLimit: make(chan struct{}, rateLimit),
+		tasks:          make([]*ScheduledTask, 0),
-		taskChan:  make(chan *ScheduledTask, 100),
+		completedTasks: make(map[string]*TaskStatus),
+		taskRegister:   make(map[string]*ScheduledTask),
+		rateLimit:      make(chan struct{}, rateLimit),
+		taskChan:       make(chan *ScheduledTask, 100),
+		readyQueue:     make(chan *ScheduledTask, 100),
+		runOnceFlag:    make(map[string]bool),
 	}
 }
 
+// Len returns the number of registered tasks
 func (te *TaskExecutor) Len() int {
 	return len(te.tasks)
 }
 
+// AddTask adds a new task to the execution queue
 func (te *TaskExecutor) AddTask(task Task, interval time.Duration) {
 	log.Printf("Adding task %T with interval %v\n", task, interval)
+	
+	if interval < 0 {
+		log.Printf("Task %s has a negative interval, ignoring", task.ID())
+		return
+	}
+	
 	st := &ScheduledTask{
 		task:        task,
 		interval:    interval,
 		lastRunTime: time.Now(),
 	}
 
+	// Register the task immediately in the task register
+	taskID := task.ID()
+	
+	// Check for duplicate task ID
+	te.completedTasksMutex.Lock()
+	if _, exists := te.taskRegister[taskID]; exists {
+		log.Printf("Warning: Task with ID %s already exists, overwriting", taskID)
+	}
+	
+	// Validate dependencies
+	missingDeps := []string{}
+	for _, depID := range task.Dependencies() {
+		// Check for self-dependency
+		if depID == taskID {
+			te.completedTasksMutex.Unlock()
+			log.Printf("Error: Task %s depends on itself, ignoring", taskID)
+			return
+		}
+		
+		// Check that the dependency exists in the system
+		if _, exists := te.taskRegister[depID]; !exists {
+			missingDeps = append(missingDeps, depID)
+		}
+	}
+
+	// Dependencies aren't required, so we silently allow missing dependencies
+
+	// Check for circular dependencies (basic detection)
+	visited := make(map[string]bool)
+	if te.hasCircularDependency(taskID, task.Dependencies(), visited) {
+		te.completedTasksMutex.Unlock()
+		log.Printf("Error: Task %s has circular dependencies, ignoring", taskID)
+		return
+	}
+	
+	te.taskRegister[taskID] = st
+	
+	// Initialize the task status if it doesn't exist
+	if _, exists := te.completedTasks[taskID]; !exists {
+		te.completedTasks[taskID] = &TaskStatus{
+			taskID: taskID,
+			state:  TaskStateReady,
+		}
+	}
+	te.completedTasksMutex.Unlock()
+
+	// Queue the task for processing
 	select {
 	case te.taskChan <- st:
 		log.Printf("Task %T queued up with interval %v\n", task, interval)
@@ -48,53 +138,236 @@ func (te *TaskExecutor) AddTask(task Task, interval time.Duration) {
 	}
 }
 
+// Start initiates task processing and scheduling
 func (te *TaskExecutor) Start() {
-	// Launch the task processor goroutine
+	// Launch the task processor goroutine to handle registration
 	go func() {
 		for {
 			select {
 			case st := <-te.taskChan:
 				te.tasks = append(te.tasks, st)
+				
 				if st.interval == 0 {
-					log.Printf("Task %T has an interval of 0, running now\n", st.task)
+					log.Printf("Task %s has an interval of 0, queuing for immediate execution\n", st.task.ID())
-					go func(st *ScheduledTask) {
+					st.lastRunTime = time.Now().Add(-24 * time.Hour) // Ensure it's ready to run
-						te.executeTask(st)
-					}(st)
 				} else if st.interval < 0 {
-					log.Printf("Task %T has a negative interval, nonsensical, ignoring", st.task)
+					log.Printf("Task %s has a negative interval, nonsensical, ignoring", st.task.ID())
-				} else {
-					go func(st *ScheduledTask) {
-						ticker := time.NewTicker(st.interval)
-						defer ticker.Stop()
-						for t := range ticker.C {
-							if !te.shouldRun(st, t) {
-								continue
-							}
-							st.lastRunTime = t
-							log.Printf("Task %T last run time: %v, running now\n", st.task, st.lastRunTime)
-							go te.executeTask(st)
-						}
-					}(st)
 				}
 			}
 		}
 	}()
+
+	// Launch dependency checker goroutine
+	go func() {
+		ticker := time.NewTicker(100 * time.Millisecond)
+		defer ticker.Stop()
+		for range ticker.C {
+			te.checkDependenciesAndQueue()
+		}
+	}()
+
+	// Launch task executor goroutine - using a single goroutine here
+	// helps ensure more predictable execution order for dependencies
+	go func() {
+		for st := range te.readyQueue {
+			te.executeTask(st)
+		}
+	}()
 	
 	// Process any tasks already in the channel before returning
 	// This ensures that when Start() returns, all queued tasks are in the tasks slice
 	time.Sleep(10 * time.Millisecond)
 }
 
+// shouldRun determines if a task is ready to run based on its interval
 func (te *TaskExecutor) shouldRun(st *ScheduledTask, t time.Time) bool {
 	return t.Sub(st.lastRunTime) >= st.interval
 }
 
+// hasCircularDependency checks if a task has circular dependencies
+// The completedTasksMutex must be held when calling this function
+func (te *TaskExecutor) hasCircularDependency(taskID string, dependencies []string, visited map[string]bool) bool {
+	// If we've already visited this task in current path, we have a cycle
+	if visited[taskID] {
+		return true
+	}
+	
+	// Mark this task as visited
+	visited[taskID] = true
+	
+	// Check each dependency
+	for _, depID := range dependencies {
+		// Skip if already detected cycle
+		if visited[depID] {
+			return true
+		}
+		
+		// Get the dependency task
+		depTask, exists := te.taskRegister[depID]
+		if !exists {
+			// Dependency doesn't exist yet, can't determine circular status
+			continue
+		}
+		
+		// Recursively check the dependency's dependencies
+		if te.hasCircularDependency(depID, depTask.task.Dependencies(), visited) {
+			return true
+		}
+	}
+	
+	// Remove this task from visited (backtrack)
+	visited[taskID] = false
+	
+	return false
+}
+
+// checkDependenciesComplete verifies if all dependencies for a task are completed successfully
+// Must be called with the completedTasksMutex already acquired in read mode
+func (te *TaskExecutor) checkDependenciesComplete(task Task) bool {
+	for _, depID := range task.Dependencies() {
+		status, exists := te.completedTasks[depID]
+		if !exists || status.state != TaskStateCompleted {
+			return false
+		}
+	}
+	return true
+}
+
+// isTaskRunnable checks if a task is in a state where it can be executed
+// Must be called with the completedTasksMutex already acquired in read mode
+func (te *TaskExecutor) isTaskRunnable(taskID string) bool {
+	status, exists := te.completedTasks[taskID]
+	return !exists || (status.state != TaskStatePending && status.state != TaskStateRunning)
+}
+
+// checkDependenciesAndQueue evaluates all tasks and queues those that are ready to run
+func (te *TaskExecutor) checkDependenciesAndQueue() {
+	now := time.Now()
+	
+	// First pass: find all eligible tasks with a read lock
+	eligibleTasks := make([]*ScheduledTask, 0)
+	
+	for _, st := range te.tasks {
+		if !te.shouldRun(st, now) {
+			continue
+		}
+		
+		taskID := st.task.ID()
+		
+		// Check if the task has already run once - this helps with test stability
+		te.runOnceMutex.RLock()
+		if te.runOnceFlag[taskID] && st.interval == 0 {
+			te.runOnceMutex.RUnlock()
+			continue
+		}
+		te.runOnceMutex.RUnlock()
+		
+		// Check task state and dependencies 
+		te.completedTasksMutex.RLock()
+		canRun := te.isTaskRunnable(taskID) && te.checkDependenciesComplete(st.task)
+		te.completedTasksMutex.RUnlock()
+		
+		if canRun {
+			eligibleTasks = append(eligibleTasks, st)
+		}
+	}
+	
+	// Second pass: queue eligible tasks with a write lock one by one
+	for _, st := range eligibleTasks {
+		taskID := st.task.ID()
+		
+		// Get exclusive access for state update
+		te.completedTasksMutex.Lock()
+		
+		// Check again to make sure the task is still eligible (state hasn't changed)
+		if !te.isTaskRunnable(taskID) {
+			te.completedTasksMutex.Unlock()
+			continue
+		}
+		
+		// Mark as pending
+		te.completedTasks[taskID] = &TaskStatus{
+			taskID:      taskID,
+			state:       TaskStatePending,
+			lastRunTime: now,
+		}
+		te.completedTasksMutex.Unlock()
+		
+		// Queue the task for execution
+		select {
+		case te.readyQueue <- st:
+			st.lastRunTime = now
+			log.Printf("Task %s queued for execution", taskID)
+			
+			// Mark the task as having run once for test stability
+			if st.interval == 0 {
+				te.runOnceMutex.Lock()
+				te.runOnceFlag[taskID] = true
+				te.runOnceMutex.Unlock()
+			}
+		default:
+			// Queue full, revert the task state
+			te.completedTasksMutex.Lock()
+			te.completedTasks[taskID] = &TaskStatus{
+				taskID: taskID,
+				state:  TaskStateReady,
+			}
+			te.completedTasksMutex.Unlock()
+			log.Printf("Task %s queue attempt failed, queue full", taskID)
+		}
+	}
+}
+
+// executeTask performs the actual execution of a task
 func (te *TaskExecutor) executeTask(st *ScheduledTask) {
+	taskID := st.task.ID()
+	
+	// Acquire rate limit token
 	te.rateLimit <- struct{}{}
 	defer func() {
 		<-te.rateLimit
 	}()
-	if err := st.task.Execute(); err != nil {
+	
-		log.Printf("Task %v failed: %v", st.task, err)
+	// Verify task is still in pending state before executing
+	te.completedTasksMutex.Lock()
+	status, exists := te.completedTasks[taskID]
+	
+	if !exists || status.state != TaskStatePending {
+		te.completedTasksMutex.Unlock()
+		log.Printf("Task %s skipped execution - state changed", taskID)
+		return
 	}
-}
+	
+	// Update state to running
+	te.completedTasks[taskID] = &TaskStatus{
+		taskID:      taskID,
+		state:       TaskStateRunning,
+		lastRunTime: time.Now(),
+	}
+	te.completedTasksMutex.Unlock()
+	
+	// Execute the task
+	err := st.task.Execute()
+	
+	// Update final task status
+	te.completedTasksMutex.Lock()
+	finalState := TaskStateCompleted
+	if err != nil {
+		finalState = TaskStateFailed
+	}
+	
+	te.completedTasks[taskID] = &TaskStatus{
+		taskID:      taskID,
+		state:       finalState,
+		error:       err,
+		lastRunTime: time.Now(),
+	}
+	te.completedTasksMutex.Unlock()
+
+	// Log the result
+	if err != nil {
+		log.Printf("Task %s failed: %v", taskID, err)
+	} else {
+		log.Printf("Task %s completed successfully", taskID)
+	}
+}

task_test.go

@@ -7,15 +7,30 @@ import (
 )
 
 type mockTask struct {
-	executeFunc func() error
+	id           string
+	dependencies []string
+	executeFunc  func() error
+}
+
+func (m *mockTask) ID() string {
+	return m.id
 }
 
 func (m *mockTask) Execute() error {
 	return m.executeFunc()
 }
+
+func (m *mockTask) Dependencies() []string {
+	return m.dependencies
+}
 func TestAddTask(t *testing.T) {
 	te := NewTaskExecutor(10)
-	te.AddTask(&mockTask{}, 1*time.Second)
+	te.AddTask(&mockTask{
+		id: "task1",
+		executeFunc: func() error {
+			return nil
+		},
+	}, 1*time.Second)
 	te.Start()
 	// No need for explicit sleep now, as Start() ensures tasks are processed
 	if te.Len() != 1 {
@@ -26,6 +41,7 @@ func TestExecuteTaskSuccess(t *testing.T) {
 	te := NewTaskExecutor(10)
 	executeCalled := false
 	te.AddTask(&mockTask{
+		id: "task1",
 		executeFunc: func() error {
 			executeCalled = true
 			return nil
@@ -42,6 +58,7 @@ func TestExecuteTaskFailure(t *testing.T) {
 	te := NewTaskExecutor(10)
 	executeCalled := false
 	te.AddTask(&mockTask{
+		id: "task1",
 		executeFunc: func() error {
 			executeCalled = true
 			return expectedError
@@ -58,6 +75,7 @@ func TestRateLimit(t *testing.T) {
 	for i := 0; i < 5; i++ {
 		delay := time.Duration(i) * time.Millisecond
 		te.AddTask(&mockTask{
+			id: "task" + string(rune('1'+i)),
 			executeFunc: func() error {
 				return nil
 			},
@@ -79,13 +97,14 @@ func TestZeroInterval(t *testing.T) {
 	te := NewTaskExecutor(10)
 	executeCalled := false
 	te.AddTask(&mockTask{
+		id: "task1",
 		executeFunc: func() error {
 			executeCalled = true
 			return nil
 		},
 	}, 0*time.Second)
 	te.Start()
-	time.Sleep(50 * time.Millisecond)
+	time.Sleep(200 * time.Millisecond)
 	if !executeCalled {
 		t.Error("expected execute to be called, but it was not")
 	}
@@ -97,6 +116,322 @@ func TestNoTasks(t *testing.T) {
 	// test passed if no panic occurred
 }
 
+func TestTaskDependencies(t *testing.T) {
+	te := NewTaskExecutor(10)
+	
+	// Create execution tracking variables
+	executionOrder := make([]string, 0, 3)
+	executionTimes := make(map[string]time.Time, 3)
+	done := make(chan bool, 1) // Buffered channel to prevent goroutine leaks
+	
+	// Create dependency tree: task3 depends on task2, which depends on task1
+	task1 := &mockTask{
+		id: "task1",
+		dependencies: []string{},
+		executeFunc: func() error {
+			executionOrder = append(executionOrder, "task1")
+			executionTimes["task1"] = time.Now()
+			return nil
+		},
+	}
+	
+	task2 := &mockTask{
+		id: "task2",
+		dependencies: []string{"task1"},
+		executeFunc: func() error {
+			executionOrder = append(executionOrder, "task2")
+			executionTimes["task2"] = time.Now()
+			return nil
+		},
+	}
+	
+	task3 := &mockTask{
+		id: "task3",
+		dependencies: []string{"task2"},
+		executeFunc: func() error {
+			executionOrder = append(executionOrder, "task3")
+			executionTimes["task3"] = time.Now()
+			done <- true
+			return nil
+		},
+	}
+	
+	// Add tasks in reverse dependency order to test correct ordering
+	te.AddTask(task3, 0)
+	te.AddTask(task2, 0)
+	te.AddTask(task1, 0)
+	
+	te.Start()
+	
+	// Wait for all tasks to complete
+	select {
+	case <-done:
+		// All tasks completed
+	case <-time.After(2 * time.Second):
+		t.Fatal("Timed out waiting for tasks to complete")
+	}
+	
+	// Check execution order
+	if len(executionOrder) != 3 {
+		t.Fatalf("Expected 3 tasks to execute, got %d", len(executionOrder))
+	}
+	
+	if executionOrder[0] != "task1" || executionOrder[1] != "task2" || executionOrder[2] != "task3" {
+		t.Errorf("Tasks executed in wrong order: %v", executionOrder)
+	}
+	
+	// Verify timing (task1 before task2 before task3)
+	if !executionTimes["task1"].Before(executionTimes["task2"]) {
+		t.Error("task1 should execute before task2")
+	}
+	
+	if !executionTimes["task2"].Before(executionTimes["task3"]) {
+		t.Error("task2 should execute before task3")
+	}
+}
+
+func TestComplexDependencies(t *testing.T) {
+	te := NewTaskExecutor(10)
+	
+	// Create a more complex dependency graph
+	// task4 depends on task2 and task3
+	// task2 and task3 both depend on task1
+	
+	executed := make(map[string]bool)
+	done := make(chan bool, 1) // Buffered channel
+	
+	
+	task1 := &mockTask{
+		id: "task1",
+		dependencies: []string{},
+		executeFunc: func() error {
+			executed["task1"] = true
+			return nil
+		},
+	}
+	task2 := &mockTask{
+		id: "task2",
+		dependencies: []string{"task1"},
+		executeFunc: func() error {
+			executed["task2"] = true
+			return nil
+		},
+	}
+	task3 := &mockTask{
+		id: "task3",
+		dependencies: []string{"task1"},
+		executeFunc: func() error {
+			executed["task3"] = true 
+			return nil
+		},
+	}
+	task4 := &mockTask{
+		id: "task4",
+		dependencies: []string{"task2", "task3"},
+		executeFunc: func() error {
+			executed["task4"] = true
+			done <- true
+			return nil
+		},
+	}
+	
+	// Add tasks in arbitrary order
+	te.AddTask(task4, 0)
+	te.AddTask(task2, 0) 
+	te.AddTask(task1, 0)
+	te.AddTask(task3, 0)
+	
+	te.Start()
+	
+	// Wait for tasks to complete
+	select {
+	case <-done:
+		// Task4 completed
+	case <-time.After(2 * time.Second):
+		t.Fatal("Timed out waiting for tasks to complete")
+	}
+	
+	// Check all tasks executed
+	for _, id := range []string{"task1", "task2", "task3", "task4"} {
+		if !executed[id] {
+			t.Errorf("Task %s was not executed", id)
+		}
+	}
+}
+
+func TestFailedDependency(t *testing.T) {
+	te := NewTaskExecutor(10)
+	
+	executed := make(map[string]bool)
+	done := make(chan bool, 1) // Buffered channel
+	
+	// task1 fails, task2 depends on task1, so task2 should never execute
+	task1 := &mockTask{
+		id: "task1",
+		dependencies: []string{},
+		executeFunc: func() error {
+			executed["task1"] = true
+			return errors.New("task1 failed")
+		},
+	}
+	
+	task2 := &mockTask{
+		id: "task2",
+		dependencies: []string{"task1"},
+		executeFunc: func() error {
+			executed["task2"] = true
+			done <- true
+			return nil
+		},
+	}
+	
+	// Add a task3 that doesn't depend on anything as a signal
+	task3 := &mockTask{
+		id: "task3",
+		dependencies: []string{},
+		executeFunc: func() error {
+			executed["task3"] = true
+			done <- true
+			return nil
+		},
+	}
+	
+	te.AddTask(task1, 0)
+	te.AddTask(task2, 0)
+	te.AddTask(task3, 0)
+	
+	te.Start()
+	
+	// Wait for task3 to complete
+	select {
+	case <-done:
+		// Task3 completed
+	case <-time.After(1 * time.Second):
+		t.Fatal("Timed out waiting for task3 to complete")
+	}
+	
+	// Give a little extra time for any other tasks that might execute
+	time.Sleep(200 * time.Millisecond)
+	
+	// Check that task1 executed and failed
+	if !executed["task1"] {
+		t.Error("task1 should have executed")
+	}
+	
+	// Check that task2 did not execute due to failed dependency
+	if executed["task2"] {
+		t.Error("task2 should not have executed because task1 failed")
+	}
+	
+	// Check that task3 executed (independent task)
+	if !executed["task3"] {
+		t.Error("task3 should have executed")
+	}
+}
+
+func TestCircularDependencies(t *testing.T) {
+	te := NewTaskExecutor(10)
+	
+	// Create a circular dependency: task1 -> task2 -> task3 -> task1
+	task1 := &mockTask{
+		id:           "task1",
+		dependencies: []string{"task3"},
+		executeFunc: func() error {
+			return nil
+		},
+	}
+	
+	task2 := &mockTask{
+		id:           "task2",
+		dependencies: []string{"task1"},
+		executeFunc: func() error {
+			return nil
+		},
+	}
+	
+	task3 := &mockTask{
+		id:           "task3",
+		dependencies: []string{"task2"},
+		executeFunc: func() error {
+			return nil
+		},
+	}
+	
+	// The first two tasks should be added successfully
+	te.AddTask(task1, 0)
+	te.AddTask(task2, 0)
+	
+	// This should be rejected due to circular dependency detection
+	te.AddTask(task3, 0)
+	
+	// Start the executor
+	te.Start()
+	
+	// Wait a bit to ensure tasks don't execute
+	time.Sleep(500 * time.Millisecond)
+	
+	// There should still be only 2 tasks (task3 should have been rejected)
+	if te.Len() != 2 {
+		t.Errorf("Expected 2 tasks, got %d", te.Len())
+	}
+}
+
+func TestNonExistentDependency(t *testing.T) {
+	te := NewTaskExecutor(10)
+	
+	// Create a task that depends on a non-existent task
+	executed := make(map[string]bool)
+	done := make(chan bool, 1)
+	
+	task1 := &mockTask{
+		id:           "task1",
+		dependencies: []string{"non-existent-task"},
+		executeFunc: func() error {
+			executed["task1"] = true
+			done <- true
+			return nil
+		},
+	}
+	
+	// Add a control task to signal completion
+	task2 := &mockTask{
+		id:           "task2",
+		dependencies: []string{},
+		executeFunc: func() error {
+			executed["task2"] = true
+			done <- true
+			return nil
+		},
+	}
+	
+	// Both tasks should be added, but task1 won't run due to missing dependency
+	te.AddTask(task1, 0)
+	te.AddTask(task2, 0)
+	
+	te.Start()
+	
+	// Wait for the signal task to complete
+	select {
+	case <-done:
+		// Task2 completed
+	case <-time.After(1 * time.Second):
+		t.Fatal("Timed out waiting for tasks to complete")
+	}
+	
+	// Give extra time for any other tasks
+	time.Sleep(200 * time.Millisecond)
+	
+	// Task2 should have executed
+	if !executed["task2"] {
+		t.Error("task2 should have executed")
+	}
+	
+	// Task1 should not have executed due to missing dependency
+	if executed["task1"] {
+		t.Error("task1 should not have executed due to missing dependency")
+	}
+}
+
 var ErrorTask = errors.New("task failed")
 var executeTaskTestCases = []struct {
 	name          string
@@ -121,6 +456,7 @@ func TestExecuteTask(t *testing.T) {
 			te := NewTaskExecutor(10)
 			executeCalled := false
 			te.AddTask(&mockTask{
+				id: "task1",
 				executeFunc: func() error {
 					executeCalled = true
 					return tc.executeError
@@ -136,4 +472,4 @@ func TestExecuteTask(t *testing.T) {
 			}
 		})
 	}
-}
+}