diff --git a/src/convert/char.rs b/src/convert/char.rs
index 004072d..3747dce 100644
--- a/src/convert/char.rs
+++ b/src/convert/char.rs
@@ -11,15 +11,14 @@ pub trait CharConverter {
 }
 
 pub struct CharConverterImpl {
-    chars: String,
-    count: f32,
+    chars: Vec<char>,
 }
 
 impl CharConverterImpl {
     pub fn new(chars: String) -> Self {
-        let count = chars.chars().count() as f32;
+        let chars = chars.chars().collect();
 
-        Self { chars, count }
+        Self { chars }
     }
 }
 
@@ -28,10 +27,10 @@ impl CharConverter for CharConverterImpl {
         if level < 0.0 {
             CharSample::Clear
         } else if level < 1.0 {
-            let index = (level * self.count) as usize;
-            let char = self.chars.chars().nth(index).unwrap();
+            let len = self.chars.len() as f32;
+            let index = (level * len) as usize;
 
-            CharSample::Draw(char)
+            CharSample::Draw(self.chars[index])
         } else {
             CharSample::Keep
         }
diff --git a/src/pattern/circle.rs b/src/pattern/circle.rs
index 1bd745e..8726598 100644
--- a/src/pattern/circle.rs
+++ b/src/pattern/circle.rs
@@ -38,7 +38,7 @@ mod test {
     fn sample() {
         let config = Config {
             size: Vector::new(10.0, 20.0),
-            step: 0.0,
+            ..Config::default()
         };
         let pattern = CircleFactory::new().create(&config);
 
diff --git a/src/pattern/line.rs b/src/pattern/line.rs
index eb8aa5c..f20cf3d 100644
--- a/src/pattern/line.rs
+++ b/src/pattern/line.rs
@@ -36,7 +36,7 @@ mod test {
     fn sample() {
         let config = Config {
             size: Vector::new(20.0, 0.0),
-            step: 0.0,
+            ..Config::default()
         };
         let pattern = LineFactory::new().create(&config);
 
diff --git a/src/pattern/rhombus.rs b/src/pattern/rhombus.rs
index 480041c..aa7c071 100644
--- a/src/pattern/rhombus.rs
+++ b/src/pattern/rhombus.rs
@@ -38,7 +38,7 @@ mod test {
     fn sample() {
         let config = Config {
             size: Vector::new(10.0, 5.0),
-            step: 0.0,
+            ..Config::default()
         };
         let pattern = RhombusFactory::new().create(&config);
 
diff --git a/src/pattern/wheel.rs b/src/pattern/wheel.rs
index 5569fe8..b833a79 100644
--- a/src/pattern/wheel.rs
+++ b/src/pattern/wheel.rs
@@ -37,7 +37,7 @@ mod test {
     fn sample() {
         let config = Config {
             size: Vector::new(10.0, 20.0),
-            step: 0.0,
+            ..Config::default()
         };
         let pattern = WheelFactory::new().create(&config);
 
diff --git a/src/transform/shift.rs b/src/transform/shift.rs
index 39f090d..12b0d64 100644
--- a/src/transform/shift.rs
+++ b/src/transform/shift.rs
@@ -50,8 +50,8 @@ mod test {
     #[test]
     fn sample_shifted() {
         let config = Config {
-            size: Vector::default(),
             step: 0.4,
+            ..Config::default()
         };
         let mut child = MockPatternFactory::new();
         child.expect_create().returning(|_| {