diff --git a/src/expression/Expression_test.go b/src/expression/Expression_test.go
index 3954923..6fab56c 100644
--- a/src/expression/Expression_test.go
+++ b/src/expression/Expression_test.go
@@ -31,16 +31,6 @@ func TestEachLeaf(t *testing.T) {
 	assert.Equal(t, err.Error(), "error")
 }
 
-func TestRemoveChild(t *testing.T) {
-	src := []byte("(1+2-3*4)+(5*6-7+8)")
-	tokens := token.Tokenize(src)
-	expr := expression.Parse(tokens)
-	left := expr.Children[0]
-	right := expr.Children[1]
-	expr.RemoveChild(left)
-	assert.Equal(t, expr.Children[0], right)
-}
-
 func TestNilExpression(t *testing.T) {
 	src := []byte("")
 	tokens := token.Tokenize(src)
@@ -53,4 +43,31 @@ func TestNilGroup(t *testing.T) {
 	tokens := token.Tokenize(src)
 	expr := expression.Parse(tokens)
 	assert.Nil(t, expr)
+}
+
+func TestRemoveChild(t *testing.T) {
+	src := []byte("(1+2-3*4)+(5*6-7+8)")
+	tokens := token.Tokenize(src)
+	expr := expression.Parse(tokens)
+	left := expr.Children[0]
+	right := expr.Children[1]
+	expr.RemoveChild(left)
+	assert.Equal(t, expr.Children[0], right)
+}
+
+func TestSource(t *testing.T) {
+	src := []byte("(1+2-3*4)+(5*6-7+8)")
+	tokens := token.Tokenize(src)
+	expr := expression.Parse(tokens)
+	assert.DeepEqual(t, expr.Source, tokens)
+	assert.DeepEqual(t, expr.Children[0].Source, tokens[1:8])
+	assert.DeepEqual(t, expr.Children[1].Source, tokens[11:18])
+	sources := []string{}
+
+	expr.EachLeaf(func(leaf *expression.Expression) error {
+		sources = append(sources, leaf.Source.String(src))
+		return nil
+	})
+
+	assert.DeepEqual(t, sources, []string{"1", "2", "3", "4", "5", "6", "7", "8"})
 }
\ No newline at end of file