Completed Day 1

A bit behind! :o

src/day1.rs

@@ -0,0 +1,31 @@
+use std::error::Error;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+
+const INPUT: &str = "inputs/1.txt";
+
+pub fn solve() -> Result<i32, Box<Error>> {
+    calculate_resulting_frequency(INPUT)
+}
+
+fn calculate_resulting_frequency(filename: &str) -> Result<i32, Box<Error>> {
+    let mut freq: i32 = 0;
+    let file = File::open(filename)?;
+    for line in BufReader::new(file).lines() {
+        let adjustment: i32 = line?.parse()?;
+        freq += adjustment;
+    }
+    Ok(freq)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TEST_INPUT: &str = "inputs/1_test.txt";
+
+    #[test]
+    fn finds_resulting_frequency() {
+        assert_eq!(calculate_resulting_frequency(TEST_INPUT).unwrap(), 3);
+    }
+}

src/main.rs

@@ -0,0 +1,6 @@
+mod day1;
+
+fn main() {
+    println!("Day 1:");
+    println!("{}", day1::solve().unwrap());
+}