diff --git a/src/settings/mod.rs b/src/settings/mod.rs
index cb9599f..441d571 100644
--- a/src/settings/mod.rs
+++ b/src/settings/mod.rs
@@ -227,8 +227,12 @@ impl Settings {
     ///
     /// # Example
     ///
-    /// ```no_run
-    /// let s = lang_evolve_core::settings::Settings::from("settings.yml");
+    /// ```
+    /// # use lang_evolve_core::settings::Settings;
+    /// # use std::path::Path;
+    /// # let s = Settings::default();
+    /// # s.export(Path::new("settings.yml"));
+    /// let s = Settings::from("settings.yml");
     /// ```
     pub fn from<S>(s: S) -> std::io::Result<Self>
     where
@@ -245,6 +249,20 @@ impl Settings {
     ///
     /// * `from` - Regex that should match the text to be replaced
     /// * `to` - Regex that should replace some text
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use lang_evolve_core::settings::Settings;
+    /// let mut settings = Settings::default();
+    /// settings.add_rule("ha", "wa");
+    ///
+    /// use std::str::FromStr;
+    /// let reference = Settings::from_str(
+    ///     r#"{"version":"1","categories":{},"rules":[{"from":"ha","to":"wa"}]}"#)
+    ///     .unwrap();
+    /// assert_eq!(reference, settings);
+    /// ```
     pub fn add_rule(&mut self, from: &str, to: &str) {
         self.rules.push(Rule::new(from, to))
     }
@@ -255,6 +273,20 @@ impl Settings {
     ///
     /// * `name` - Name of the category
     /// * `content` - Content of the category, phonemes
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use lang_evolve_core::settings::Settings;
+    /// let mut settings = Settings::default();
+    /// settings.add_category("C", "abcde");
+    ///
+    /// use std::str::FromStr;
+    /// let reference = Settings::from_str(
+    ///     r#"{"version":"1","categories":{"C": "abcde"},"rules":[]}"#)
+    ///     .unwrap();
+    /// assert_eq!(reference, settings);
+    /// ```
     pub fn add_category(&mut self, name: &str, content: &str) {
         self.categories.insert(String::from(name), String::from(content));
     }
@@ -309,6 +341,7 @@ impl Settings {
         RULESET_CURRENT_VERSION.to_string()
     }
 
+    /// Transform input rules into Regexes that can be understood by Rust.
     fn update_rules(&self) -> std::result::Result<Vec<Rule>, String> {
         let rules = self.rules.clone();
         let rules: Vec<Rule> = rules
diff --git a/src/settings/rule/mod.rs b/src/settings/rule/mod.rs
index f14fe36..bbc9883 100644
--- a/src/settings/rule/mod.rs
+++ b/src/settings/rule/mod.rs
@@ -44,6 +44,22 @@ impl Rule {
         }
     }
 
+    /// Detect the number of categories in a rule
+    ///
+    /// For a rule, this function detects the number of categories set in the
+    /// `from` member of a `Rule` and in its `to` member. The result is returned
+    /// as a tuple of `u8`s.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # #[path = "mod.rs"]
+    /// # mod rule;
+    /// # use rule::Rule;
+    /// let rule = Rule::new("%Bea*i+", "a%A%C");
+    /// let nb_rules = rule.detect_number_categories();
+    /// assert_eq!((1 as u8, 2 as u8), nb_rules);
+    /// ```
     pub fn detect_number_categories(&self) -> (u8, u8) {
         let captures_from = self.from.to_string().matches('%').count() as u8;
         let captures_to = self.to.matches('%').count() as u8;
@@ -94,6 +110,22 @@ impl Rule {
 }
 
 impl From<String> for Rule {
+    /// Allow to create a rule from a single `String`
+    ///
+    /// It is possible to create a rule from a string, delimited by a `>`. This
+    /// means a rule like `%C>%D` will be interpreted as going from `%C` to
+    /// `%D`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # #[path = "mod.rs"]
+    /// # mod rule;
+    /// # use rule::Rule;
+    /// let rule1 = Rule::new("%C", "%D");
+    /// let rule2 = Rule::from(String::from("%C>%D"));
+    /// assert_eq!(rule1, rule2);
+    /// ```
     fn from(source: String) -> Self {
         let components: Vec<&str> = source.split_terminator('>').collect();
         Rule::new(components[0], components[1])
@@ -101,6 +133,21 @@ impl From<String> for Rule {
 }
 
 impl PartialEq for Rule {
+    /// Equality between `Rule` structs
+    ///
+    /// This allows for equality comparison between two `Rule` structs.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # #[path = "mod.rs"]
+    /// # mod rule;
+    /// use rule::Rule;
+    /// let rule1 = Rule::new("%C", "%D");
+    /// let rule2 = Rule::from("%C>%D");
+    /// assert!(rule1 == rule2);
+    /// assert!(rule2 == rule1);
+    /// ```
     fn eq(&self, other: &Self) -> bool {
         self.from == other.from && self.to == other.to
     }