pila: allow publicly to use custom Stack implementation

pila/stack.go

@@ -43,13 +43,20 @@ type Stack struct {
 }
 
 // NewStack creates a new Stack given a name and a creation date,
-// without an association to any Database.
+// without an association to any Database. It uses the default
+// ./pkg/stack implementation.
 func NewStack(name string, t time.Time) *Stack {
+	return NewStackWithCustomImplementation(name, t, stack.NewStack())
+}
+
+// NewStackWithCustomImplementation creates a new Stack given a name, a creation date,
+// and a stack.Stacker implementation without an association to any Database.
+func NewStackWithCustomImplementation(name string, t time.Time, stack stack.Stacker) *Stack {
 	s := &Stack{}
 	s.Name = name
 	s.SetID()
 	s.CreatedAt = t
-	s.base = stack.NewStack()
+	s.base = stack
 	return s
 }
 

pila/stack_test.go

@@ -7,6 +7,14 @@ import (
 	"time"
 )
 
+type TestStack struct{}
+
+func (s *TestStack) Push(element interface{}) { return }
+func (s *TestStack) Pop() (interface{}, bool) { return nil, false }
+func (s *TestStack) Size() int                { return 0 }
+func (s *TestStack) Peek() interface{}        { return nil }
+func (s *TestStack) Flush()                   { return }
+
 func TestNewStack(t *testing.T) {
 	now := time.Now()
 	stack := NewStack("test-stack", now)
@@ -35,6 +43,34 @@ func TestNewStack(t *testing.T) {
 	}
 }
 
+func TestNewStackWithCustomImplementation(t *testing.T) {
+	now := time.Now()
+	stack := NewStackWithCustomImplementation("test-stack", now, &TestStack{})
+
+	if stack == nil {
+		t.Fatal("stack is nil")
+	}
+
+	if stack.ID.String() != "2f44edeaa249ba81db20e9ddf000ba65" {
+		t.Errorf("stack.ID is %s, expected %s", stack.ID.String(), "2f44edeaa249ba81db20e9ddf000ba65")
+	}
+	if stack.Name != "test-stack" {
+		t.Errorf("stack.Name is %s, expected %s", stack.Name, "test-stack")
+	}
+	if stack.Database != nil {
+		t.Error("stack.Database is not nil")
+	}
+	if stack.CreatedAt != now {
+		t.Errorf("stack.CreatedAt is %v, expected %v", stack.CreatedAt, now)
+	}
+	if stack.base == nil {
+		t.Fatalf("stack.base is nil")
+	}
+	if stack.base.Size() != 0 {
+		t.Fatalf("stack.base.Size() is %d, expected %d", stack.base.Size(), 0)
+	}
+}
+
 func TestSetDatabase(t *testing.T) {
 	db := NewDatabase("test-db")
 	stack := NewStack("test-stack", time.Now())