diff --git a/.editorconfig b/.editorconfig
index 8b423bf..8d59d07 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -9,7 +9,3 @@ end_of_line = lf
 charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
-
-[*.txt]
-trim_trailing_whitespace = unset
-insert_final_newline = unset
diff --git a/day_1/src/lib.rs b/day_1/src/lib.rs
new file mode 100644
index 0000000..89c029e
--- /dev/null
+++ b/day_1/src/lib.rs
@@ -0,0 +1,79 @@
+pub fn part_1(input: &str) -> usize {
+    input
+        .lines()
+        .map(|line| {
+            let characters_digits = line
+                .chars()
+                .filter(|&character| character.is_ascii_digit())
+                .collect::<Vec<char>>();
+
+            let first_digit = characters_digits.first().unwrap_or(&'0').to_owned();
+            let last_digit = characters_digits.last().unwrap_or(&'0').to_owned();
+            let number = format!("{}{}", first_digit, last_digit);
+            let number: usize = number.parse().expect("Should parse as a `usize`.");
+            number
+        })
+        .sum()
+}
+
+pub fn part_2(input: &str) -> usize {
+    let numbers_spelled_out_with_letters = [
+        "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
+    ];
+
+    input
+        .lines()
+        .map(|line| {
+            let mut characters_digits: Vec<char> = vec![];
+            let mut temporary = String::from("");
+            for character in line.chars() {
+                temporary += &character.to_string();
+
+                let mut temporary_spelled_number_index = None;
+                for (index, spelled_number) in numbers_spelled_out_with_letters.iter().enumerate() {
+                    if temporary.contains(spelled_number) {
+                        temporary_spelled_number_index = Some(index);
+                        break;
+                    }
+                }
+                if let Some(temporary_spelled_number_index) = temporary_spelled_number_index {
+                    let number = temporary_spelled_number_index + 1;
+                    characters_digits.push(
+                        number
+                            .to_string()
+                            .chars()
+                            .next()
+                            .expect("Number should be single-character digit."),
+                    );
+                    temporary = character.to_string();
+                }
+
+                if character.is_ascii_digit() {
+                    characters_digits.push(character);
+                    temporary = String::from("");
+                }
+            }
+
+            let first_digit = characters_digits.first().unwrap_or(&'0').to_owned();
+            let last_digit = characters_digits.last().unwrap_or(&'0').to_owned();
+            let number = format!("{}{}", first_digit, last_digit);
+            let number: usize = number.parse().expect("Should parse as a `usize`.");
+            number
+        })
+        .sum()
+}
+
+#[cfg(test)]
+mod day_1_tests {
+    use super::*;
+
+    #[test]
+    fn test_part_1_example() {
+        assert_eq!(part_1(include_str!("../input_example_1.txt")), 142);
+    }
+
+    #[test]
+    fn test_part_2_example() {
+        assert_eq!(part_2(include_str!("../input_example_2.txt")), 281);
+    }
+}
diff --git a/day_1/src/main.rs b/day_1/src/main.rs
index 06ec0d4..e6160aa 100644
--- a/day_1/src/main.rs
+++ b/day_1/src/main.rs
@@ -1,67 +1,4 @@
-fn part_1(input: &str) -> i32 {
-    input
-        .lines()
-        .map(|line| {
-            let characters_digits = line
-                .chars()
-                .filter(|&character| character.is_ascii_digit())
-                .collect::<Vec<char>>();
-
-            let first_digit = characters_digits.first().unwrap_or(&'0').to_owned();
-            let last_digit = characters_digits.last().unwrap_or(&'0').to_owned();
-            let number = format!("{}{}", first_digit, last_digit);
-            let number: i32 = number.parse().expect("Should parse as a i32.");
-            number
-        })
-        .sum()
-}
-
-fn part_2(input: &str) -> i32 {
-    let numbers_spelled_out_with_letters = [
-        "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
-    ];
-
-    input
-        .lines()
-        .map(|line| {
-            let mut characters_digits: Vec<char> = vec![];
-            let mut temporary = String::from("");
-            for character in line.chars() {
-                temporary += &character.to_string();
-
-                let mut temporary_spelled_number_index = None;
-                for (index, spelled_number) in numbers_spelled_out_with_letters.iter().enumerate() {
-                    if temporary.contains(spelled_number) {
-                        temporary_spelled_number_index = Some(index);
-                        break;
-                    }
-                }
-                if let Some(temporary_spelled_number_index) = temporary_spelled_number_index {
-                    let number = temporary_spelled_number_index + 1;
-                    characters_digits.push(
-                        number
-                            .to_string()
-                            .chars()
-                            .next()
-                            .expect("Number should be single-character digit."),
-                    );
-                    temporary = character.to_string();
-                }
-
-                if character.is_ascii_digit() {
-                    characters_digits.push(character);
-                    temporary = String::from("");
-                }
-            }
-
-            let first_digit = characters_digits.first().unwrap_or(&'0').to_owned();
-            let last_digit = characters_digits.last().unwrap_or(&'0').to_owned();
-            let number = format!("{}{}", first_digit, last_digit);
-            let number: i32 = number.parse().expect("Should parse as a number.");
-            number
-        })
-        .sum()
-}
+use day_1::{part_1, part_2};
 
 fn main() {
     let input = include_str!("../input.txt");
@@ -69,18 +6,3 @@ fn main() {
     println!("Answer Part 1: {}", part_1(input));
     println!("Answer Part 2: {}", part_2(input));
 }
-
-#[cfg(test)]
-mod day_1_tests {
-    use super::*;
-
-    #[test]
-    fn test_part_1_example() {
-        assert_eq!(142, part_1(include_str!("../input_example_1.txt")));
-    }
-
-    #[test]
-    fn test_part_2_example() {
-        assert_eq!(281, part_2(include_str!("../input_example_2.txt")));
-    }
-}