Move code into library crate for testing

.idea/code.iml

@@ -3,6 +3,9 @@
   <component name="NewModuleRootManager">
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src/lib/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/tests" isTestSource="true" />
+      <excludeFolder url="file://$MODULE_DIR$/src/lib/target" />
       <excludeFolder url="file://$MODULE_DIR$/target" />
     </content>
     <orderEntry type="inheritedJdk" />

src/lib.rs

@@ -0,0 +1,2 @@
+mod common;
+pub mod solvers;

src/main.rs

@@ -1,5 +1,4 @@
-mod common;
+use advent_of_code_2025::solvers;
-mod solvers;
 
 fn main() {
     println!("### Advent of Code 2025 ###\n");

src/solvers.rs

@@ -25,7 +25,8 @@ pub trait Solver {
 
 // The "../../data" and "../../../data" paths are useful for running the binary from
 // "target/release/" directory with "data/" directory in package root or parent directory.
-const DATA_PATHS: &'static [&'static str] = &["./data", "../data", "../../data", "../../../data"];
+pub const DATA_PATHS: &'static [&'static str] =
+    &["./data", "../data", "../../data", "../../../data"];
 
 pub fn run<S: Solver>(solver: S) {
     println!(