adding stack tests

Signed-off-by: David Lawrence <david.lawrence@docker.com> (github: endophage)

tuf/utils/stack.go

@@ -36,7 +36,7 @@ func (s *Stack) Pop() (interface{}, error) {
 		*s = (*s)[:l-1]
 		return item, nil
 	}
-	return nil, ErrEmptyStack{action: "pop"}
+	return nil, ErrEmptyStack{action: "Pop"}
 }
 
 func (s *Stack) PopString() (string, error) {
@@ -49,7 +49,7 @@ func (s *Stack) PopString() (string, error) {
 		}
 		return "", ErrBadTypeCast{}
 	}
-	return "", ErrEmptyStack{action: "pop"}
+	return "", ErrEmptyStack{action: "PopString"}
 }
 
 func (s Stack) Empty() bool {

tuf/utils/stack_test.go

@@ -0,0 +1,69 @@
+package utils
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCreateStack(t *testing.T) {
+	s := NewStack()
+	assert.NotNil(t, s)
+}
+
+func TestPush(t *testing.T) {
+	s := NewStack()
+	s.Push("foo")
+	assert.Len(t, *s, 1)
+	assert.Equal(t, "foo", (*s)[0])
+}
+
+func TestPop(t *testing.T) {
+	s := NewStack()
+	s.Push("foo")
+	i, err := s.Pop()
+	assert.NoError(t, err)
+	assert.Len(t, *s, 0)
+	assert.IsType(t, "", i)
+	assert.Equal(t, "foo", i)
+}
+
+func TestPopEmpty(t *testing.T) {
+	s := NewStack()
+	_, err := s.Pop()
+	assert.Error(t, err)
+	assert.IsType(t, ErrEmptyStack{}, err)
+}
+
+func TestPopString(t *testing.T) {
+	s := NewStack()
+	s.Push("foo")
+	i, err := s.PopString()
+	assert.NoError(t, err)
+	assert.Len(t, *s, 0)
+	assert.Equal(t, "foo", i)
+}
+
+func TestPopStringWrongType(t *testing.T) {
+	s := NewStack()
+	s.Push(123)
+	_, err := s.PopString()
+	assert.Error(t, err)
+	assert.IsType(t, ErrBadTypeCast{}, err)
+}
+
+func TestPopStringEmpty(t *testing.T) {
+	s := NewStack()
+	_, err := s.PopString()
+	assert.Error(t, err)
+	assert.IsType(t, ErrEmptyStack{}, err)
+}
+
+func TestEmpty(t *testing.T) {
+	s := NewStack()
+	assert.True(t, s.Empty())
+	s.Push("foo")
+	assert.False(t, s.Empty())
+	s.Pop()
+	assert.True(t, s.Empty())
+}