diff --git a/src/check.rs b/src/check.rs
index 32990c2..1cd9d9d 100644
--- a/src/check.rs
+++ b/src/check.rs
@@ -7,9 +7,7 @@ use crate::{
 	utils::{log_failure, log_process, log_success},
 };
 
-/// TODO: fill with appropriate rules
-const FORMAT_CONFIG: &str = r#"{BasedOnStyle: llvm}"#;
-
+mod formatting;
 mod testables;
 
 pub fn main(files: Vec<String>) {
@@ -35,7 +33,7 @@ pub enum Diff {
 
 fn check_formatting(file: String) {
 	let content = fs::read_to_string(&file).unwrap();
-	let formatted = FormatTask::new(file.clone(), FORMAT_CONFIG.into()).run();
+	let formatted = FormatTask::new(file.clone(), formatting::formatted_config()).run();
 	let mut line_number = 0usize;
 	let mut invalid = false;
 	let differences = diff::lines(&content, &formatted)
@@ -94,7 +92,7 @@ fn check_formatting(file: String) {
 
 pub fn format(files: Vec<String>) {
 	for file in files {
-		let mut formatted = FormatTask::new(file.clone(), FORMAT_CONFIG.into()).run();
+		let mut formatted = FormatTask::new(file.clone(), formatting::formatted_config()).run();
 		if !formatted.ends_with('\n') {
 			formatted += "\n";
 		}
diff --git a/src/check/formatting.rs b/src/check/formatting.rs
new file mode 100644
index 0000000..01aacda
--- /dev/null
+++ b/src/check/formatting.rs
@@ -0,0 +1,17 @@
+pub type StaticConf = [(&'static str, &'static str)];
+
+/// TODO: fill with appropriate rules
+pub const FORMAT_CONFIG: &StaticConf = &[
+	// (key, value)
+	("BasedOnStyle", "GNU"),
+	("IndentWidth", "4"),
+];
+
+pub fn formatted_config() -> String {
+	let middle = FORMAT_CONFIG
+		.into_iter()
+		.map(|(key, value)| format!("{key}: {value}"))
+		.collect::<Vec<_>>()
+		.join(", ");
+	format!("{{ {middle} }}")
+}
diff --git a/src/check/testables.rs b/src/check/testables.rs
index a696f19..9226aab 100644
--- a/src/check/testables.rs
+++ b/src/check/testables.rs
@@ -1,18 +1,12 @@
-fn ends_with_newline(source: String) -> Result<(), String> {
-	if !source.ends_with('\n') {
-		Err("source does not end with newline".into())
-	} else {
-		Ok(())
-	}
-}
+pub type RuleResult = Result<(), String>;
 
 pub struct Rule {
 	name: String,
-	test: Box<dyn Fn(String) -> Result<(), String>>,
+	test: Box<dyn Fn(String) -> RuleResult>,
 }
 
 impl Rule {
-	pub fn new(name: impl ToString, test: impl 'static + Fn(String) -> Result<(), String>) -> Self {
+	pub fn new(name: impl ToString, test: impl 'static + Fn(String) -> RuleResult) -> Self {
 		let name = name.to_string();
 		let test = Box::new(test);
 		Self { name, test }
@@ -22,15 +16,32 @@ impl Rule {
 		&self.name
 	}
 
-	pub fn test(&self, source: String) -> Result<(), String> {
+	pub fn test(&self, source: String) -> RuleResult {
 		(self.test)(source)
 	}
 }
 
+fn ends_with_newline(source: String) -> RuleResult {
+	if !source.ends_with('\n') {
+		Err("source does not end with newline".into())
+	} else {
+		Ok(())
+	}
+}
+
+fn function_under_50l(source: String) -> RuleResult {
+	for character in source.chars() {
+		let c: char = character;
+	}
+
+	Ok(())
+}
+
 /// TODO: fill with appropriate rules
 pub fn tests() -> Vec<Rule> {
 	vec![
 		// rules
 		Rule::new("ends_with_newline", ends_with_newline),
+		Rule::new("function_under_50l", function_under_50l),
 	]
 }
diff --git a/src/main.rs b/src/main.rs
index 138d37e..0b44c4b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -84,6 +84,7 @@ fn append_includes(list: &mut Vec<String>) {
 fn compilation_args() -> Vec<String> {
 	let mut args = vec![
 		"-Wall".to_string(),
+		"-fsanitize=address".to_string(),
 		"-Wextra".to_string(),
 		"-std=c99".to_string(),
 	];
diff --git a/src/tasks.rs b/src/tasks.rs
index 86be5a4..aa17132 100644
--- a/src/tasks.rs
+++ b/src/tasks.rs
@@ -1,11 +1,11 @@
 use std::{
 	fs,
 	path::PathBuf,
-	process::{Command, ExitStatus, Stdio},
+	process::{exit, Command, ExitStatus, Stdio},
 };
 
 use crate::utils::{
-	log_command_run, log_separator_bottom, log_separator_top, tmp_file_path, Apply,
+	log_command_run, log_failure, log_separator_bottom, log_separator_top, tmp_file_path, Apply,
 };
 
 pub struct CompileTask {
@@ -145,10 +145,20 @@ impl FormatTask {
 			.arg(format!("-style={config}"))
 			.stdout(Stdio::piped())
 			.stderr(Stdio::piped());
-		command.status().unwrap();
 
-		let result = command.output().unwrap().stdout;
-		String::from_utf8(result).unwrap()
+		let status = command.status().unwrap();
+		let out = command.output().unwrap().stdout;
+		let out = String::from_utf8(out).unwrap();
+		let err = command.output().unwrap().stderr;
+		let err = String::from_utf8(err).unwrap();
+		if !status.success() {
+			log_failure("failed formatting");
+			println!("{out}");
+			eprintln!("{err}");
+			exit(1);
+		}
+
+		out
 	}
 }