diff --git a/CHANGELOG.md b/CHANGELOG.md
index 20b07e5..222cf48 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@
 
 ### Removed
 
+ * Removed integration tests from shipped crate
+
 ### Changed
 
 ### Fixed
diff --git a/src/interface/mod.rs b/src/interface/mod.rs
new file mode 100644
index 0000000..4445fcb
--- /dev/null
+++ b/src/interface/mod.rs
@@ -0,0 +1,72 @@
+use token;
+use tree;
+use Configuration;
+use EmptyConfiguration;
+use Error;
+use Node;
+use Value;
+
+/// Evaluate the given expression string.
+///
+/// # Examples
+///
+/// ```rust
+/// use evalexpr::*;
+///
+/// assert_eq!(eval("1 + 2 + 3"), Ok(Value::from(6)));
+/// ```
+///
+/// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
+pub fn eval(string: &str) -> Result<Value, Error> {
+    eval_with_configuration(string, &EmptyConfiguration)
+}
+
+/// Evaluate the given expression string with the given configuration.
+///
+/// # Examples
+///
+/// ```rust
+/// use evalexpr::*;
+///
+/// let mut configuration = HashMapConfiguration::new();
+/// configuration.insert_variable("one", 1);
+/// configuration.insert_variable("two", 2);
+/// configuration.insert_variable("three", 3);
+/// assert_eq!(eval_with_configuration("one + two + three", &configuration), Ok(Value::from(6)));
+/// ```
+///
+/// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
+pub fn eval_with_configuration(
+    string: &str,
+    configuration: &Configuration,
+) -> Result<Value, Error> {
+    tree::tokens_to_operator_tree(token::tokenize(string)?)?.eval_with_configuration(configuration)
+}
+
+/// Build the operator tree for the given expression string.
+///
+/// The operator tree can later on be evaluated directly.
+/// This saves runtime if a single expression should be evaluated multiple times, for example with differing configurations.
+///
+/// # Examples
+///
+/// ```rust
+/// use evalexpr::*;
+///
+/// let precomputed = build_operator_tree("one + two + three").unwrap();
+///
+/// let mut configuration = HashMapConfiguration::new();
+/// configuration.insert_variable("one", 1);
+/// configuration.insert_variable("two", 2);
+/// configuration.insert_variable("three", 3);
+///
+/// assert_eq!(precomputed.eval_with_configuration(&configuration), Ok(Value::from(6)));
+///
+/// configuration.insert_variable("three", 5);
+/// assert_eq!(precomputed.eval_with_configuration(&configuration), Ok(Value::from(8)));
+/// ```
+///
+/// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
+pub fn build_operator_tree(string: &str) -> Result<Node, Error> {
+    tree::tokens_to_operator_tree(token::tokenize(string)?)
+}
diff --git a/src/lib.rs b/src/lib.rs
index 4b1ea57..5b892df 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -211,6 +211,7 @@ extern crate core;
 mod configuration;
 pub mod error;
 mod function;
+mod interface;
 mod operator;
 mod token;
 mod tree;
@@ -221,409 +222,6 @@ mod value;
 pub use configuration::{Configuration, EmptyConfiguration, HashMapConfiguration};
 pub use error::Error;
 pub use function::Function;
+pub use interface::*;
 pub use tree::Node;
-pub use value::Value;
-
-/// Evaluate the given expression string.
-///
-/// # Examples
-///
-/// ```rust
-/// use evalexpr::*;
-///
-/// assert_eq!(eval("1 + 2 + 3"), Ok(Value::from(6)));
-/// ```
-///
-/// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
-pub fn eval(string: &str) -> Result<Value, Error> {
-    eval_with_configuration(string, &EmptyConfiguration)
-}
-
-/// Evaluate the given expression string with the given configuration.
-///
-/// # Examples
-///
-/// ```rust
-/// use evalexpr::*;
-///
-/// let mut configuration = HashMapConfiguration::new();
-/// configuration.insert_variable("one", 1);
-/// configuration.insert_variable("two", 2);
-/// configuration.insert_variable("three", 3);
-/// assert_eq!(eval_with_configuration("one + two + three", &configuration), Ok(Value::from(6)));
-/// ```
-///
-/// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
-pub fn eval_with_configuration(
-    string: &str,
-    configuration: &Configuration,
-) -> Result<Value, Error> {
-    tree::tokens_to_operator_tree(token::tokenize(string)?)?.eval_with_configuration(configuration)
-}
-
-/// Build the operator tree for the given expression string.
-///
-/// The operator tree can later on be evaluated directly.
-/// This saves runtime if a single expression should be evaluated multiple times, for example with differing configurations.
-///
-/// # Examples
-///
-/// ```rust
-/// use evalexpr::*;
-///
-/// let precomputed = build_operator_tree("one + two + three").unwrap();
-///
-/// let mut configuration = HashMapConfiguration::new();
-/// configuration.insert_variable("one", 1);
-/// configuration.insert_variable("two", 2);
-/// configuration.insert_variable("three", 3);
-///
-/// assert_eq!(precomputed.eval_with_configuration(&configuration), Ok(Value::from(6)));
-///
-/// configuration.insert_variable("three", 5);
-/// assert_eq!(precomputed.eval_with_configuration(&configuration), Ok(Value::from(8)));
-/// ```
-///
-/// *See the [crate doc](index.html) for more examples and explanations of the expression format.*
-pub fn build_operator_tree(string: &str) -> Result<Node, Error> {
-    tree::tokens_to_operator_tree(token::tokenize(string)?)
-}
-
-#[cfg(test)]
-mod test {
-    use crate::{eval, value::Value};
-    use configuration::HashMapConfiguration;
-    use error::{expect_number, Error};
-    use eval_with_configuration;
-    use value::IntType;
-    use Function;
-
-    #[test]
-    fn test_unary_examples() {
-        assert_eq!(eval("3"), Ok(Value::Int(3)));
-        assert_eq!(eval("3.3"), Ok(Value::Float(3.3)));
-        assert_eq!(eval("true"), Ok(Value::Boolean(true)));
-        assert_eq!(eval("false"), Ok(Value::Boolean(false)));
-        assert_eq!(
-            eval("blub"),
-            Err(Error::VariableIdentifierNotFound("blub".to_string()))
-        );
-        assert_eq!(eval("-3"), Ok(Value::Int(-3)));
-        assert_eq!(eval("-3.6"), Ok(Value::Float(-3.6)));
-        assert_eq!(eval("----3"), Ok(Value::Int(3)));
-    }
-
-    #[test]
-    fn test_binary_examples() {
-        assert_eq!(eval("1+3"), Ok(Value::Int(4)));
-        assert_eq!(eval("3+1"), Ok(Value::Int(4)));
-        assert_eq!(eval("3-5"), Ok(Value::Int(-2)));
-        assert_eq!(eval("5-3"), Ok(Value::Int(2)));
-        assert_eq!(eval("5 / 4"), Ok(Value::Int(1)));
-        assert_eq!(eval("5 *3"), Ok(Value::Int(15)));
-        assert_eq!(eval("1.0+3"), Ok(Value::Float(4.0)));
-        assert_eq!(eval("3.0+1"), Ok(Value::Float(4.0)));
-        assert_eq!(eval("3-5.0"), Ok(Value::Float(-2.0)));
-        assert_eq!(eval("5-3.0"), Ok(Value::Float(2.0)));
-        assert_eq!(eval("5 / 4.0"), Ok(Value::Float(1.25)));
-        assert_eq!(eval("5.0 *3"), Ok(Value::Float(15.0)));
-        assert_eq!(eval("5.0 *-3"), Ok(Value::Float(-15.0)));
-        assert_eq!(eval("5.0 *- 3"), Ok(Value::Float(-15.0)));
-        assert_eq!(eval("5.0 * -3"), Ok(Value::Float(-15.0)));
-        assert_eq!(eval("5.0 * - 3"), Ok(Value::Float(-15.0)));
-        assert_eq!(eval("-5.0 *-3"), Ok(Value::Float(15.0)));
-        assert_eq!(eval("3+-1"), Ok(Value::Int(2)));
-        assert_eq!(eval("-3-5"), Ok(Value::Int(-8)));
-        assert_eq!(eval("-5--3"), Ok(Value::Int(-2)));
-    }
-
-    #[test]
-    fn test_arithmetic_precedence_examples() {
-        assert_eq!(eval("1+3-2"), Ok(Value::Int(2)));
-        assert_eq!(eval("3+1*5"), Ok(Value::Int(8)));
-        assert_eq!(eval("2*3-5"), Ok(Value::Int(1)));
-        assert_eq!(eval("5-3/3"), Ok(Value::Int(4)));
-        assert_eq!(eval("5 / 4*2"), Ok(Value::Int(2)));
-        assert_eq!(eval("1-5 *3/15"), Ok(Value::Int(0)));
-        assert_eq!(eval("15/7/2.0"), Ok(Value::Float(1.0)));
-        assert_eq!(eval("15.0/7/2"), Ok(Value::Float(15.0 / 7.0 / 2.0)));
-        assert_eq!(eval("15.0/-7/2"), Ok(Value::Float(15.0 / -7.0 / 2.0)));
-        assert_eq!(eval("-15.0/7/2"), Ok(Value::Float(-15.0 / 7.0 / 2.0)));
-        assert_eq!(eval("-15.0/7/-2"), Ok(Value::Float(-15.0 / 7.0 / -2.0)));
-    }
-
-    #[test]
-    fn test_braced_examples() {
-        assert_eq!(eval("(1)"), Ok(Value::Int(1)));
-        assert_eq!(eval("( 1.0 )"), Ok(Value::Float(1.0)));
-        assert_eq!(eval("( true)"), Ok(Value::Boolean(true)));
-        assert_eq!(eval("( -1 )"), Ok(Value::Int(-1)));
-        assert_eq!(eval("-(1)"), Ok(Value::Int(-1)));
-        assert_eq!(eval("-(1 + 3) * 7"), Ok(Value::Int(-28)));
-        assert_eq!(eval("(1 * 1) - 3"), Ok(Value::Int(-2)));
-        assert_eq!(eval("4 / (2 * 2)"), Ok(Value::Int(1)));
-        assert_eq!(eval("7/(7/(7/(7/(7/(7)))))"), Ok(Value::Int(1)));
-    }
-
-    #[test]
-    fn test_mod_examples() {
-        assert_eq!(eval("1 % 4"), Ok(Value::Int(1)));
-        assert_eq!(eval("6 % 4"), Ok(Value::Int(2)));
-        assert_eq!(eval("1 % 4 + 2"), Ok(Value::Int(3)));
-    }
-
-    #[test]
-    fn test_pow_examples() {
-        assert_eq!(eval("1 ^ 4"), Ok(Value::Float(1.0)));
-        assert_eq!(eval("6 ^ 4"), Ok(Value::Float(6.0f64.powf(4.0))));
-        assert_eq!(eval("1 ^ 4 + 2"), Ok(Value::Float(3.0)));
-        assert_eq!(eval("2 ^ (4 + 2)"), Ok(Value::Float(64.0)));
-    }
-
-    #[test]
-    fn test_boolean_examples() {
-        assert_eq!(eval("true && false"), Ok(Value::Boolean(false)));
-        assert_eq!(
-            eval("true && false || true && true"),
-            Ok(Value::Boolean(true))
-        );
-        assert_eq!(eval("5 > 4 && 1 <= 1"), Ok(Value::Boolean(true)));
-        assert_eq!(eval("5.0 <= 4.9 || !(4 > 3.5)"), Ok(Value::Boolean(false)));
-    }
-
-    #[test]
-    fn test_with_configuration() {
-        let mut configuration = HashMapConfiguration::new();
-        configuration.insert_variable("tr".to_string(), Value::Boolean(true));
-        configuration.insert_variable("fa".to_string(), Value::Boolean(false));
-        configuration.insert_variable("five".to_string(), Value::Int(5));
-        configuration.insert_variable("six".to_string(), Value::Int(6));
-        configuration.insert_variable("half".to_string(), Value::Float(0.5));
-        configuration.insert_variable("zero".to_string(), Value::Int(0));
-
-        assert_eq!(
-            eval_with_configuration("tr", &configuration),
-            Ok(Value::Boolean(true))
-        );
-        assert_eq!(
-            eval_with_configuration("fa", &configuration),
-            Ok(Value::Boolean(false))
-        );
-        assert_eq!(
-            eval_with_configuration("tr && false", &configuration),
-            Ok(Value::Boolean(false))
-        );
-        assert_eq!(
-            eval_with_configuration("five + six", &configuration),
-            Ok(Value::Int(11))
-        );
-        assert_eq!(
-            eval_with_configuration("five * half", &configuration),
-            Ok(Value::Float(2.5))
-        );
-        assert_eq!(
-            eval_with_configuration("five < six && true", &configuration),
-            Ok(Value::Boolean(true))
-        );
-    }
-
-    #[test]
-    fn test_functions() {
-        let mut configuration = HashMapConfiguration::new();
-        configuration.insert_function(
-            "sub2".to_string(),
-            Function::new(
-                Some(1),
-                Box::new(|arguments| {
-                    if let Value::Int(int) = arguments[0] {
-                        Ok(Value::Int(int - 2))
-                    } else if let Value::Float(float) = arguments[0] {
-                        Ok(Value::Float(float - 2.0))
-                    } else {
-                        Err(Error::expected_number(arguments[0].clone()))
-                    }
-                }),
-            ),
-        );
-        configuration.insert_variable("five".to_string(), Value::Int(5));
-
-        assert_eq!(
-            eval_with_configuration("sub2 5", &configuration),
-            Ok(Value::Int(3))
-        );
-        assert_eq!(
-            eval_with_configuration("sub2(5)", &configuration),
-            Ok(Value::Int(3))
-        );
-        assert_eq!(
-            eval_with_configuration("sub2 five", &configuration),
-            Ok(Value::Int(3))
-        );
-        assert_eq!(
-            eval_with_configuration("sub2(five)", &configuration),
-            Ok(Value::Int(3))
-        );
-        assert_eq!(
-            eval_with_configuration("sub2(3) + five", &configuration),
-            Ok(Value::Int(6))
-        );
-    }
-
-    #[test]
-    fn test_n_ary_functions() {
-        let mut configuration = HashMapConfiguration::new();
-        configuration.insert_function(
-            "sub2",
-            Function::new(
-                Some(1),
-                Box::new(|arguments| {
-                    if let Value::Int(int) = arguments[0] {
-                        Ok(Value::Int(int - 2))
-                    } else if let Value::Float(float) = arguments[0] {
-                        Ok(Value::Float(float - 2.0))
-                    } else {
-                        Err(Error::expected_number(arguments[0].clone()))
-                    }
-                }),
-            ),
-        );
-        configuration.insert_function(
-            "avg",
-            Function::new(
-                Some(2),
-                Box::new(|arguments| {
-                    expect_number(&arguments[0])?;
-                    expect_number(&arguments[1])?;
-
-                    if let (Value::Int(a), Value::Int(b)) = (&arguments[0], &arguments[1]) {
-                        Ok(Value::Int((a + b) / 2))
-                    } else {
-                        Ok(Value::Float(
-                            (arguments[0].as_float()? + arguments[1].as_float()?) / 2.0,
-                        ))
-                    }
-                }),
-            ),
-        );
-        configuration.insert_function(
-            "muladd",
-            Function::new(
-                Some(3),
-                Box::new(|arguments| {
-                    expect_number(&arguments[0])?;
-                    expect_number(&arguments[1])?;
-                    expect_number(&arguments[2])?;
-
-                    if let (Value::Int(a), Value::Int(b), Value::Int(c)) =
-                        (&arguments[0], &arguments[1], &arguments[2])
-                    {
-                        Ok(Value::Int(a * b + c))
-                    } else {
-                        Ok(Value::Float(
-                            arguments[0].as_float()? * arguments[1].as_float()?
-                                + arguments[2].as_float()?,
-                        ))
-                    }
-                }),
-            ),
-        );
-        configuration.insert_function(
-            "count",
-            Function::new(
-                None,
-                Box::new(|arguments| Ok(Value::Int(arguments.len() as IntType))),
-            ),
-        );
-        configuration.insert_variable("five".to_string(), Value::Int(5));
-
-        assert_eq!(
-            eval_with_configuration("avg(7, 5)", &configuration),
-            Ok(Value::Int(6))
-        );
-        assert_eq!(
-            eval_with_configuration("avg(sub2 5, 5)", &configuration),
-            Ok(Value::Int(4))
-        );
-        assert_eq!(
-            eval_with_configuration("sub2(avg(3, 6))", &configuration),
-            Ok(Value::Int(2))
-        );
-        assert_eq!(
-            eval_with_configuration("sub2 avg(3, 6)", &configuration),
-            Ok(Value::Int(2))
-        );
-        assert_eq!(
-            eval_with_configuration("muladd(3, 6, -4)", &configuration),
-            Ok(Value::Int(14))
-        );
-        assert_eq!(
-            eval_with_configuration("count()", &configuration),
-            Err(Error::wrong_operator_argument_amount(0, 1))
-        );
-        assert_eq!(
-            eval_with_configuration("count(3, 5.5, 2)", &configuration),
-            Ok(Value::Int(3))
-        );
-        assert_eq!(
-            eval_with_configuration("count 5", &configuration),
-            Ok(Value::Int(1))
-        );
-
-        assert_eq!(
-            eval_with_configuration("min(4.0, 3)", &configuration),
-            Ok(Value::Int(3))
-        );
-        assert_eq!(
-            eval_with_configuration("max(4.0, 3)", &configuration),
-            Ok(Value::Float(4.0))
-        );
-    }
-
-    #[test]
-    fn test_errors() {
-        assert_eq!(
-            eval("-true"),
-            Err(Error::expected_number(Value::Boolean(true)))
-        );
-        assert_eq!(
-            eval("1-true"),
-            Err(Error::expected_number(Value::Boolean(true)))
-        );
-        assert_eq!(
-            eval("true-"),
-            Err(Error::wrong_operator_argument_amount(1, 2))
-        );
-        assert_eq!(eval("!(()true)"), Err(Error::AppendedToLeafNode));
-    }
-
-    #[test]
-    fn test_no_panic() {
-        assert!(eval(&format!(
-            "{} + {}",
-            IntType::max_value(),
-            IntType::max_value()
-        ))
-        .is_err());
-        assert!(eval(&format!(
-            "-{} - {}",
-            IntType::max_value(),
-            IntType::max_value()
-        ))
-        .is_err());
-        assert!(eval(&format!("-(-{} - 1)", IntType::max_value())).is_err());
-        assert!(eval(&format!(
-            "{} * {}",
-            IntType::max_value(),
-            IntType::max_value()
-        ))
-        .is_err());
-        assert!(eval(&format!("{} / {}", IntType::max_value(), 0)).is_err());
-        assert!(eval(&format!("{} % {}", IntType::max_value(), 0)).is_err());
-        assert!(eval(&format!(
-            "{} ^ {}",
-            IntType::max_value(),
-            IntType::max_value()
-        ))
-        .is_ok());
-    }
-}
+pub use value::{FloatType, IntType, Value};
diff --git a/tests/integration.rs b/tests/integration.rs
new file mode 100644
index 0000000..36c5f74
--- /dev/null
+++ b/tests/integration.rs
@@ -0,0 +1,338 @@
+extern crate evalexpr;
+
+use evalexpr::{error::*, *};
+
+#[test]
+fn test_unary_examples() {
+    assert_eq!(eval("3"), Ok(Value::Int(3)));
+    assert_eq!(eval("3.3"), Ok(Value::Float(3.3)));
+    assert_eq!(eval("true"), Ok(Value::Boolean(true)));
+    assert_eq!(eval("false"), Ok(Value::Boolean(false)));
+    assert_eq!(
+        eval("blub"),
+        Err(Error::VariableIdentifierNotFound("blub".to_string()))
+    );
+    assert_eq!(eval("-3"), Ok(Value::Int(-3)));
+    assert_eq!(eval("-3.6"), Ok(Value::Float(-3.6)));
+    assert_eq!(eval("----3"), Ok(Value::Int(3)));
+}
+
+#[test]
+fn test_binary_examples() {
+    assert_eq!(eval("1+3"), Ok(Value::Int(4)));
+    assert_eq!(eval("3+1"), Ok(Value::Int(4)));
+    assert_eq!(eval("3-5"), Ok(Value::Int(-2)));
+    assert_eq!(eval("5-3"), Ok(Value::Int(2)));
+    assert_eq!(eval("5 / 4"), Ok(Value::Int(1)));
+    assert_eq!(eval("5 *3"), Ok(Value::Int(15)));
+    assert_eq!(eval("1.0+3"), Ok(Value::Float(4.0)));
+    assert_eq!(eval("3.0+1"), Ok(Value::Float(4.0)));
+    assert_eq!(eval("3-5.0"), Ok(Value::Float(-2.0)));
+    assert_eq!(eval("5-3.0"), Ok(Value::Float(2.0)));
+    assert_eq!(eval("5 / 4.0"), Ok(Value::Float(1.25)));
+    assert_eq!(eval("5.0 *3"), Ok(Value::Float(15.0)));
+    assert_eq!(eval("5.0 *-3"), Ok(Value::Float(-15.0)));
+    assert_eq!(eval("5.0 *- 3"), Ok(Value::Float(-15.0)));
+    assert_eq!(eval("5.0 * -3"), Ok(Value::Float(-15.0)));
+    assert_eq!(eval("5.0 * - 3"), Ok(Value::Float(-15.0)));
+    assert_eq!(eval("-5.0 *-3"), Ok(Value::Float(15.0)));
+    assert_eq!(eval("3+-1"), Ok(Value::Int(2)));
+    assert_eq!(eval("-3-5"), Ok(Value::Int(-8)));
+    assert_eq!(eval("-5--3"), Ok(Value::Int(-2)));
+}
+
+#[test]
+fn test_arithmetic_precedence_examples() {
+    assert_eq!(eval("1+3-2"), Ok(Value::Int(2)));
+    assert_eq!(eval("3+1*5"), Ok(Value::Int(8)));
+    assert_eq!(eval("2*3-5"), Ok(Value::Int(1)));
+    assert_eq!(eval("5-3/3"), Ok(Value::Int(4)));
+    assert_eq!(eval("5 / 4*2"), Ok(Value::Int(2)));
+    assert_eq!(eval("1-5 *3/15"), Ok(Value::Int(0)));
+    assert_eq!(eval("15/7/2.0"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("15.0/7/2"), Ok(Value::Float(15.0 / 7.0 / 2.0)));
+    assert_eq!(eval("15.0/-7/2"), Ok(Value::Float(15.0 / -7.0 / 2.0)));
+    assert_eq!(eval("-15.0/7/2"), Ok(Value::Float(-15.0 / 7.0 / 2.0)));
+    assert_eq!(eval("-15.0/7/-2"), Ok(Value::Float(-15.0 / 7.0 / -2.0)));
+}
+
+#[test]
+fn test_braced_examples() {
+    assert_eq!(eval("(1)"), Ok(Value::Int(1)));
+    assert_eq!(eval("( 1.0 )"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("( true)"), Ok(Value::Boolean(true)));
+    assert_eq!(eval("( -1 )"), Ok(Value::Int(-1)));
+    assert_eq!(eval("-(1)"), Ok(Value::Int(-1)));
+    assert_eq!(eval("-(1 + 3) * 7"), Ok(Value::Int(-28)));
+    assert_eq!(eval("(1 * 1) - 3"), Ok(Value::Int(-2)));
+    assert_eq!(eval("4 / (2 * 2)"), Ok(Value::Int(1)));
+    assert_eq!(eval("7/(7/(7/(7/(7/(7)))))"), Ok(Value::Int(1)));
+}
+
+#[test]
+fn test_mod_examples() {
+    assert_eq!(eval("1 % 4"), Ok(Value::Int(1)));
+    assert_eq!(eval("6 % 4"), Ok(Value::Int(2)));
+    assert_eq!(eval("1 % 4 + 2"), Ok(Value::Int(3)));
+}
+
+#[test]
+fn test_pow_examples() {
+    assert_eq!(eval("1 ^ 4"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("6 ^ 4"), Ok(Value::Float(6.0f64.powf(4.0))));
+    assert_eq!(eval("1 ^ 4 + 2"), Ok(Value::Float(3.0)));
+    assert_eq!(eval("2 ^ (4 + 2)"), Ok(Value::Float(64.0)));
+}
+
+#[test]
+fn test_boolean_examples() {
+    assert_eq!(eval("true && false"), Ok(Value::Boolean(false)));
+    assert_eq!(
+        eval("true && false || true && true"),
+        Ok(Value::Boolean(true))
+    );
+    assert_eq!(eval("5 > 4 && 1 <= 1"), Ok(Value::Boolean(true)));
+    assert_eq!(eval("5.0 <= 4.9 || !(4 > 3.5)"), Ok(Value::Boolean(false)));
+}
+
+#[test]
+fn test_with_configuration() {
+    let mut configuration = HashMapConfiguration::new();
+    configuration.insert_variable("tr".to_string(), Value::Boolean(true));
+    configuration.insert_variable("fa".to_string(), Value::Boolean(false));
+    configuration.insert_variable("five".to_string(), Value::Int(5));
+    configuration.insert_variable("six".to_string(), Value::Int(6));
+    configuration.insert_variable("half".to_string(), Value::Float(0.5));
+    configuration.insert_variable("zero".to_string(), Value::Int(0));
+
+    assert_eq!(
+        eval_with_configuration("tr", &configuration),
+        Ok(Value::Boolean(true))
+    );
+    assert_eq!(
+        eval_with_configuration("fa", &configuration),
+        Ok(Value::Boolean(false))
+    );
+    assert_eq!(
+        eval_with_configuration("tr && false", &configuration),
+        Ok(Value::Boolean(false))
+    );
+    assert_eq!(
+        eval_with_configuration("five + six", &configuration),
+        Ok(Value::Int(11))
+    );
+    assert_eq!(
+        eval_with_configuration("five * half", &configuration),
+        Ok(Value::Float(2.5))
+    );
+    assert_eq!(
+        eval_with_configuration("five < six && true", &configuration),
+        Ok(Value::Boolean(true))
+    );
+}
+
+#[test]
+fn test_functions() {
+    let mut configuration = HashMapConfiguration::new();
+    configuration.insert_function(
+        "sub2".to_string(),
+        Function::new(
+            Some(1),
+            Box::new(|arguments| {
+                if let Value::Int(int) = arguments[0] {
+                    Ok(Value::Int(int - 2))
+                } else if let Value::Float(float) = arguments[0] {
+                    Ok(Value::Float(float - 2.0))
+                } else {
+                    Err(Error::expected_number(arguments[0].clone()))
+                }
+            }),
+        ),
+    );
+    configuration.insert_variable("five".to_string(), Value::Int(5));
+
+    assert_eq!(
+        eval_with_configuration("sub2 5", &configuration),
+        Ok(Value::Int(3))
+    );
+    assert_eq!(
+        eval_with_configuration("sub2(5)", &configuration),
+        Ok(Value::Int(3))
+    );
+    assert_eq!(
+        eval_with_configuration("sub2 five", &configuration),
+        Ok(Value::Int(3))
+    );
+    assert_eq!(
+        eval_with_configuration("sub2(five)", &configuration),
+        Ok(Value::Int(3))
+    );
+    assert_eq!(
+        eval_with_configuration("sub2(3) + five", &configuration),
+        Ok(Value::Int(6))
+    );
+}
+
+#[test]
+fn test_n_ary_functions() {
+    let mut configuration = HashMapConfiguration::new();
+    configuration.insert_function(
+        "sub2",
+        Function::new(
+            Some(1),
+            Box::new(|arguments| {
+                if let Value::Int(int) = arguments[0] {
+                    Ok(Value::Int(int - 2))
+                } else if let Value::Float(float) = arguments[0] {
+                    Ok(Value::Float(float - 2.0))
+                } else {
+                    Err(Error::expected_number(arguments[0].clone()))
+                }
+            }),
+        ),
+    );
+    configuration.insert_function(
+        "avg",
+        Function::new(
+            Some(2),
+            Box::new(|arguments| {
+                expect_number(&arguments[0])?;
+                expect_number(&arguments[1])?;
+
+                if let (Value::Int(a), Value::Int(b)) = (&arguments[0], &arguments[1]) {
+                    Ok(Value::Int((a + b) / 2))
+                } else {
+                    Ok(Value::Float(
+                        (arguments[0].as_float()? + arguments[1].as_float()?) / 2.0,
+                    ))
+                }
+            }),
+        ),
+    );
+    configuration.insert_function(
+        "muladd",
+        Function::new(
+            Some(3),
+            Box::new(|arguments| {
+                expect_number(&arguments[0])?;
+                expect_number(&arguments[1])?;
+                expect_number(&arguments[2])?;
+
+                if let (Value::Int(a), Value::Int(b), Value::Int(c)) =
+                    (&arguments[0], &arguments[1], &arguments[2])
+                {
+                    Ok(Value::Int(a * b + c))
+                } else {
+                    Ok(Value::Float(
+                        arguments[0].as_float()? * arguments[1].as_float()?
+                            + arguments[2].as_float()?,
+                    ))
+                }
+            }),
+        ),
+    );
+    configuration.insert_function(
+        "count",
+        Function::new(
+            None,
+            Box::new(|arguments| Ok(Value::Int(arguments.len() as IntType))),
+        ),
+    );
+    configuration.insert_variable("five".to_string(), Value::Int(5));
+
+    assert_eq!(
+        eval_with_configuration("avg(7, 5)", &configuration),
+        Ok(Value::Int(6))
+    );
+    assert_eq!(
+        eval_with_configuration("avg(sub2 5, 5)", &configuration),
+        Ok(Value::Int(4))
+    );
+    assert_eq!(
+        eval_with_configuration("sub2(avg(3, 6))", &configuration),
+        Ok(Value::Int(2))
+    );
+    assert_eq!(
+        eval_with_configuration("sub2 avg(3, 6)", &configuration),
+        Ok(Value::Int(2))
+    );
+    assert_eq!(
+        eval_with_configuration("muladd(3, 6, -4)", &configuration),
+        Ok(Value::Int(14))
+    );
+    assert_eq!(
+        eval_with_configuration("count()", &configuration),
+        Err(Error::WrongOperatorArgumentAmount {
+            actual: 0,
+            expected: 1
+        })
+    );
+    assert_eq!(
+        eval_with_configuration("count(3, 5.5, 2)", &configuration),
+        Ok(Value::Int(3))
+    );
+    assert_eq!(
+        eval_with_configuration("count 5", &configuration),
+        Ok(Value::Int(1))
+    );
+
+    assert_eq!(
+        eval_with_configuration("min(4.0, 3)", &configuration),
+        Ok(Value::Int(3))
+    );
+    assert_eq!(
+        eval_with_configuration("max(4.0, 3)", &configuration),
+        Ok(Value::Float(4.0))
+    );
+}
+
+#[test]
+fn test_errors() {
+    assert_eq!(
+        eval("-true"),
+        Err(Error::expected_number(Value::Boolean(true)))
+    );
+    assert_eq!(
+        eval("1-true"),
+        Err(Error::expected_number(Value::Boolean(true)))
+    );
+    assert_eq!(
+        eval("true-"),
+        Err(Error::WrongOperatorArgumentAmount {
+            actual: 1,
+            expected: 2
+        })
+    );
+    assert_eq!(eval("!(()true)"), Err(Error::AppendedToLeafNode));
+}
+
+#[test]
+fn test_no_panic() {
+    assert!(eval(&format!(
+        "{} + {}",
+        IntType::max_value(),
+        IntType::max_value()
+    ))
+    .is_err());
+    assert!(eval(&format!(
+        "-{} - {}",
+        IntType::max_value(),
+        IntType::max_value()
+    ))
+    .is_err());
+    assert!(eval(&format!("-(-{} - 1)", IntType::max_value())).is_err());
+    assert!(eval(&format!(
+        "{} * {}",
+        IntType::max_value(),
+        IntType::max_value()
+    ))
+    .is_err());
+    assert!(eval(&format!("{} / {}", IntType::max_value(), 0)).is_err());
+    assert!(eval(&format!("{} % {}", IntType::max_value(), 0)).is_err());
+    assert!(eval(&format!(
+        "{} ^ {}",
+        IntType::max_value(),
+        IntType::max_value()
+    ))
+    .is_ok());
+}