diff --git a/src/tests.rs b/src/tests.rs
index 82ca988..2f5674c 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -22,8 +22,7 @@ fn test_plus_one() {
                 ),
                 None
             )
-            .is_err()
-            == false
+            .is_ok()
     );
     let results = formula.run(vec![0f64, 1f64, 2f64, 3f64, 4f64, 5f64]);
     assert_eq!(results, vec![1f64, 2f64, 3f64, 4f64, 5f64, 6f64])
@@ -39,16 +38,14 @@ fn test_branch_sum() {
                 Node::function("Sum".to_string(), |inputs| inputs.iter().sum(), Some(2), 0),
                 None
             )
-            .is_err()
-            == false
+            .is_ok()
     );
     assert!(
         formula
             .modify_tree()
             .go_down(0)
             .add_node(Node::number(1f64))
-            .is_err()
-            == false
+            .is_ok()
     );
     let results = formula.run(vec![0f64, 1f64, 2f64, 3f64, 4f64, 5f64]);
     assert_eq!(results, vec![1f64, 2f64, 3f64, 4f64, 5f64, 6f64])
@@ -64,8 +61,7 @@ fn test_display_as_text() {
                 Node::function("sum".to_string(), |inputs| inputs.iter().sum(), None, 0),
                 None
             )
-            .is_err()
-            == false
+            .is_ok()
     );
     assert!(
         formula
@@ -77,8 +73,7 @@ fn test_display_as_text() {
                 Some(1),
                 0
             ))
-            .is_err()
-            == false
+            .is_ok()
     );
     assert!(
         formula
@@ -86,8 +81,7 @@ fn test_display_as_text() {
             .go_down(0)
             .go_down(1)
             .add_node(Node::variable())
-            .is_err()
-            == false
+            .is_ok()
     );
     assert_eq!(formula.as_text(), "sum(X,sin(X))".to_string());
 }