diff --git a/CHANGELOG.md b/CHANGELOG.md
index 28657458..a86bd3af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,30 @@
 
 ## [next] - 2022-MM-DD
 
+### Added
+
+- **aiken-lang**: integrated unit tests
+
+  Aiken now supports writing unit tests directly in source files using the new
+  `test` keyword. Tests are functions with no arguments that are implicitly typed
+  to `bool`. For example:
+
+  ```gleam
+  test foo () {
+    1 + 1 == 2
+  }
+  ```
+
+- **aiken**: new `--skip-tests` flag for the `check` command
+
+### Changed
+
+- **aiken**: `check` now also runs and reports on any `test` found in the project
+
+### Removed
+
+N/A
+
 ## [v0.0.26] - 2022-11-23
 
 ### Added
diff --git a/Cargo.lock b/Cargo.lock
index e49dff86..07455dc5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -59,6 +59,7 @@ dependencies = [
  "ignore",
  "indoc",
  "miette",
+ "owo-colors",
  "pallas-addresses",
  "pallas-codec",
  "pallas-crypto",
diff --git a/crates/cli/Cargo.toml b/crates/cli/Cargo.toml
index 11855d96..a6f9215c 100644
--- a/crates/cli/Cargo.toml
+++ b/crates/cli/Cargo.toml
@@ -15,6 +15,7 @@ hex = "0.4.3"
 ignore = "0.4.18"
 indoc = "1.0"
 miette = { version = "5.3.0", features = ["fancy"] }
+owo-colors = "3.5.0"
 pallas-addresses = "0.14.0"
 pallas-codec = "0.14.0"
 pallas-crypto = "0.14.0"
diff --git a/crates/cli/src/cmd/check.rs b/crates/cli/src/cmd/check.rs
index 9f99e617..1bbc1126 100644
--- a/crates/cli/src/cmd/check.rs
+++ b/crates/cli/src/cmd/check.rs
@@ -6,8 +6,17 @@ pub struct Args {
     /// Path to project
     #[clap(short, long)]
     directory: Option<PathBuf>,
+
+    /// Skip tests; run only the type-checker
+    #[clap(short, long)]
+    skip_tests: bool,
 }
 
-pub fn exec(Args { directory }: Args) -> miette::Result<()> {
-    crate::with_project(directory, |p| p.check())
+pub fn exec(
+    Args {
+        directory,
+        skip_tests,
+    }: Args,
+) -> miette::Result<()> {
+    crate::with_project(directory, |p| p.check(skip_tests))
 }
diff --git a/crates/cli/src/cmd/uplc/eval.rs b/crates/cli/src/cmd/uplc/eval.rs
index 8d251fb0..70c86858 100644
--- a/crates/cli/src/cmd/uplc/eval.rs
+++ b/crates/cli/src/cmd/uplc/eval.rs
@@ -61,7 +61,9 @@ pub fn exec(
         program = program.apply_term(&term);
     }
 
-    let (term, cost, logs) = program.eval();
+    let budget = ExBudget::default();
+
+    let (term, cost, logs) = program.eval(budget);
 
     match term {
         Ok(term) => {
@@ -74,8 +76,6 @@ pub fn exec(
         }
     }
 
-    let budget = ExBudget::default();
-
     println!(
         "\nCosts\n-----\ncpu: {}\nmemory: {}",
         budget.cpu - cost.cpu,
diff --git a/crates/cli/src/lib.rs b/crates/cli/src/lib.rs
index d5789d46..0034bf3e 100644
--- a/crates/cli/src/lib.rs
+++ b/crates/cli/src/lib.rs
@@ -1,13 +1,19 @@
-pub mod cmd;
+use std::{env, path::PathBuf};
 
-use aiken_project::{config::Config, Project};
+use aiken_project::{
+    config::Config,
+    telemetry::{self, TestInfo},
+    Project,
+};
 use miette::IntoDiagnostic;
-use std::env;
-use std::path::PathBuf;
+use owo_colors::OwoColorize;
+use uplc::machine::cost_model::ExBudget;
+
+pub mod cmd;
 
 pub fn with_project<A>(directory: Option<PathBuf>, mut action: A) -> miette::Result<()>
 where
-    A: FnMut(&mut Project) -> Result<(), aiken_project::error::Error>,
+    A: FnMut(&mut Project<Terminal>) -> Result<(), aiken_project::error::Error>,
 {
     let project_path = if let Some(d) = directory {
         d
@@ -17,7 +23,7 @@ where
 
     let config = Config::load(project_path.clone()).into_diagnostic()?;
 
-    let mut project = Project::new(config, project_path);
+    let mut project = Project::new(config, project_path, Terminal::default());
 
     let build_result = action(&mut project);
 
@@ -30,10 +36,129 @@ where
     if let Err(err) = build_result {
         err.report();
 
-        miette::bail!("failed: {} error(s), {warning_count} warning(s)", err.len(),);
+        miette::bail!("Failed: {} error(s), {warning_count} warning(s)", err.len(),);
     };
 
-    println!("\nfinished with {warning_count} warning(s)\n");
+    println!("\nFinished with {warning_count} warning(s)\n");
 
     Ok(())
 }
+
+#[derive(Debug, Default, Clone, Copy)]
+pub struct Terminal;
+
+impl telemetry::EventListener for Terminal {
+    fn handle_event(&self, event: telemetry::Event) {
+        match event {
+            telemetry::Event::StartingCompilation {
+                name,
+                version,
+                root,
+            } => {
+                println!(
+                    "{} {} {} ({})",
+                    "Compiling".bold().purple(),
+                    name.bold(),
+                    version,
+                    root.to_str().unwrap_or("").bright_blue()
+                );
+            }
+            telemetry::Event::ParsingProjectFiles => {
+                println!("{}", "...Parsing project files".bold().purple());
+            }
+            telemetry::Event::TypeChecking => {
+                println!("{}", "...Type-checking project".bold().purple());
+            }
+            telemetry::Event::GeneratingUPLC { output_path } => {
+                println!(
+                    "{} in {}",
+                    "...Generating Untyped Plutus Core".bold().purple(),
+                    output_path.to_str().unwrap_or("").bright_blue()
+                );
+            }
+            telemetry::Event::RunningTests => {
+                println!("{}\n", "...Running tests".bold().purple());
+            }
+            telemetry::Event::FinishedTests { tests } => {
+                let (max_mem, max_cpu) = tests.iter().fold(
+                    (0, 0),
+                    |(max_mem, max_cpu), TestInfo { spent_budget, .. }| {
+                        if spent_budget.mem >= max_mem && spent_budget.cpu >= max_cpu {
+                            (spent_budget.mem, spent_budget.cpu)
+                        } else if spent_budget.mem > max_mem {
+                            (spent_budget.mem, max_cpu)
+                        } else if spent_budget.cpu > max_cpu {
+                            (max_mem, spent_budget.cpu)
+                        } else {
+                            (max_mem, max_cpu)
+                        }
+                    },
+                );
+
+                let max_mem = max_mem.to_string().len() as i32;
+                let max_cpu = max_cpu.to_string().len() as i32;
+
+                for test_info in &tests {
+                    println!("{}", fmt_test(test_info, max_mem, max_cpu))
+                }
+
+                let (n_passed, n_failed) =
+                    tests
+                        .iter()
+                        .fold((0, 0), |(n_passed, n_failed), test_info| {
+                            if test_info.is_passing {
+                                (n_passed + 1, n_failed)
+                            } else {
+                                (n_passed, n_failed + 1)
+                            }
+                        });
+
+                println!(
+                    "{}",
+                    format!(
+                        "\n    Summary: {} test(s), {}; {}.",
+                        tests.len(),
+                        format!("{} passed", n_passed).bright_green(),
+                        format!("{} failed", n_failed).bright_red()
+                    )
+                    .bold()
+                )
+            }
+        }
+    }
+}
+
+fn fmt_test(test_info: &TestInfo, max_mem: i32, max_cpu: i32) -> String {
+    let TestInfo {
+        is_passing,
+        test,
+        spent_budget,
+    } = test_info;
+
+    let ExBudget { mem, cpu } = spent_budget;
+
+    format!(
+        "    [{}] [mem: {}, cpu: {}] {}::{}",
+        if *is_passing {
+            "PASS".bold().green().to_string()
+        } else {
+            "FAIL".bold().red().to_string()
+        },
+        pad_left(mem.to_string(), max_mem, " "),
+        pad_left(cpu.to_string(), max_cpu, " "),
+        test.module.blue(),
+        test.name.bright_blue()
+    )
+}
+
+fn pad_left(mut text: String, n: i32, delimiter: &str) -> String {
+    let diff = n - text.len() as i32;
+
+    if diff.is_positive() {
+        for _ in 0..diff {
+            text.insert_str(0, delimiter);
+        }
+    }
+
+    text
+}
diff --git a/crates/lang/src/ast.rs b/crates/lang/src/ast.rs
index 93a70889..3afbdd82 100644
--- a/crates/lang/src/ast.rs
+++ b/crates/lang/src/ast.rs
@@ -138,6 +138,8 @@ pub enum Definition<T, Expr, ConstantRecordTag, PackageName> {
     Use(Use<PackageName>),
 
     ModuleConstant(ModuleConstant<T, ConstantRecordTag>),
+
+    Test(Function<T, Expr>),
 }
 
 impl<A, B, C, E> Definition<A, B, C, E> {
@@ -147,7 +149,8 @@ impl<A, B, C, E> Definition<A, B, C, E> {
             | Definition::Use(Use { location, .. })
             | Definition::TypeAlias(TypeAlias { location, .. })
             | Definition::DataType(DataType { location, .. })
-            | Definition::ModuleConstant(ModuleConstant { location, .. }) => *location,
+            | Definition::ModuleConstant(ModuleConstant { location, .. })
+            | Definition::Test(Function { location, .. }) => *location,
         }
     }
 
@@ -157,7 +160,8 @@ impl<A, B, C, E> Definition<A, B, C, E> {
             Definition::Fn(Function { doc, .. })
             | Definition::TypeAlias(TypeAlias { doc, .. })
             | Definition::DataType(DataType { doc, .. })
-            | Definition::ModuleConstant(ModuleConstant { doc, .. }) => {
+            | Definition::ModuleConstant(ModuleConstant { doc, .. })
+            | Definition::Test(Function { doc, .. }) => {
                 let _ = std::mem::replace(doc, Some(new_doc));
             }
         }
diff --git a/crates/lang/src/format.rs b/crates/lang/src/format.rs
index 71e76d10..2d5b7853 100644
--- a/crates/lang/src/format.rs
+++ b/crates/lang/src/format.rs
@@ -215,7 +215,23 @@ impl<'comments> Formatter<'comments> {
                 return_annotation,
                 end_position,
                 ..
-            }) => self.definition_fn(public, name, args, return_annotation, body, *end_position),
+            }) => self.definition_fn(
+                public,
+                "fn",
+                name,
+                args,
+                return_annotation,
+                body,
+                *end_position,
+            ),
+
+            Definition::Test(Function {
+                name,
+                arguments: args,
+                body,
+                end_position,
+                ..
+            }) => self.definition_fn(&false, "test", name, args, &None, body, *end_position),
 
             Definition::TypeAlias(TypeAlias {
                 alias,
@@ -493,9 +509,11 @@ impl<'comments> Formatter<'comments> {
         commented(doc, comments)
     }
 
+    #[allow(clippy::too_many_arguments)]
     fn definition_fn<'a>(
         &mut self,
         public: &'a bool,
+        keyword: &'a str,
         name: &'a str,
         args: &'a [UntypedArg],
         return_annotation: &'a Option<Annotation>,
@@ -504,7 +522,8 @@ impl<'comments> Formatter<'comments> {
     ) -> Document<'a> {
         // Fn name and args
         let head = pub_(*public)
-            .append("fn ")
+            .append(keyword)
+            .append(" ")
             .append(name)
             .append(wrap_args(args.iter().map(|e| (self.fn_arg(e), false))));
 
diff --git a/crates/lang/src/parser.rs b/crates/lang/src/parser.rs
index d92e7e31..d2c98f1c 100644
--- a/crates/lang/src/parser.rs
+++ b/crates/lang/src/parser.rs
@@ -74,6 +74,7 @@ fn module_parser() -> impl Parser<Token, Vec<UntypedDefinition>, Error = ParseEr
         data_parser(),
         type_alias_parser(),
         fn_parser(),
+        test_parser(),
         constant_parser(),
     ))
     .repeated()
@@ -266,6 +267,36 @@ pub fn fn_parser() -> impl Parser<Token, ast::UntypedDefinition, Error = ParseEr
         )
 }
 
+pub fn test_parser() -> impl Parser<Token, ast::UntypedDefinition, Error = ParseError> {
+    just(Token::Test)
+        .ignore_then(select! {Token::Name {name} => name})
+        .then_ignore(just(Token::LeftParen))
+        .then_ignore(just(Token::RightParen))
+        .map_with_span(|name, span| (name, span))
+        .then(
+            expr_seq_parser()
+                .or_not()
+                .delimited_by(just(Token::LeftBrace), just(Token::RightBrace)),
+        )
+        .map_with_span(|((name, span_end), body), span| {
+            ast::UntypedDefinition::Test(ast::Function {
+                arguments: vec![],
+                body: body.unwrap_or(expr::UntypedExpr::Todo {
+                    kind: TodoKind::EmptyFunction,
+                    location: span,
+                    label: None,
+                }),
+                doc: None,
+                location: span_end,
+                end_position: span.end - 1,
+                name,
+                public: true,
+                return_annotation: None,
+                return_type: (),
+            })
+        })
+}
+
 fn constant_parser() -> impl Parser<Token, ast::UntypedDefinition, Error = ParseError> {
     pub_parser()
         .or_not()
diff --git a/crates/lang/src/parser/lexer.rs b/crates/lang/src/parser/lexer.rs
index 1d140384..d845b741 100644
--- a/crates/lang/src/parser/lexer.rs
+++ b/crates/lang/src/parser/lexer.rs
@@ -67,6 +67,7 @@ pub fn lexer() -> impl Parser<char, Vec<(Token, Span)>, Error = ParseError> {
         "check" => Token::Assert,
         "const" => Token::Const,
         "fn" => Token::Fn,
+        "test" => Token::Test,
         "if" => Token::If,
         "else" => Token::Else,
         "is" => Token::Is,
diff --git a/crates/lang/src/parser/token.rs b/crates/lang/src/parser/token.rs
index 8faaa339..0811268a 100644
--- a/crates/lang/src/parser/token.rs
+++ b/crates/lang/src/parser/token.rs
@@ -68,6 +68,7 @@ pub enum Token {
     Opaque,
     Pub,
     Use,
+    Test,
     Todo,
     Trace,
     Type,
@@ -145,6 +146,7 @@ impl fmt::Display for Token {
             Token::Todo => "todo",
             Token::Trace => "try",
             Token::Type => "type",
+            Token::Test => "test",
         };
         write!(f, "\"{}\"", s)
     }
diff --git a/crates/lang/src/tipo/environment.rs b/crates/lang/src/tipo/environment.rs
index ca9b6055..4f70deff 100644
--- a/crates/lang/src/tipo/environment.rs
+++ b/crates/lang/src/tipo/environment.rs
@@ -255,6 +255,7 @@ impl<'a> Environment<'a> {
             definition @ (Definition::TypeAlias { .. }
             | Definition::DataType { .. }
             | Definition::Use { .. }
+            | Definition::Test { .. }
             | Definition::ModuleConstant { .. }) => definition,
         }
     }
@@ -911,7 +912,10 @@ impl<'a> Environment<'a> {
                 }
             }
 
-            Definition::Fn { .. } | Definition::Use { .. } | Definition::ModuleConstant { .. } => {}
+            Definition::Fn { .. }
+            | Definition::Test { .. }
+            | Definition::Use { .. }
+            | Definition::ModuleConstant { .. } => {}
         }
 
         Ok(())
@@ -990,6 +994,24 @@ impl<'a> Environment<'a> {
                 }
             }
 
+            Definition::Test(Function { name, location, .. }) => {
+                hydrators.insert(name.clone(), Hydrator::new());
+                let arg_types = vec![];
+                let return_type = builtins::bool();
+                self.insert_variable(
+                    name.clone(),
+                    ValueConstructorVariant::ModuleFn {
+                        name: name.clone(),
+                        field_map: None,
+                        module: module_name.to_owned(),
+                        arity: 0,
+                        location: *location,
+                        builtin: None,
+                    },
+                    function(arg_types, return_type),
+                );
+            }
+
             Definition::DataType(DataType {
                 location,
                 public,
diff --git a/crates/lang/src/tipo/infer.rs b/crates/lang/src/tipo/infer.rs
index 907b731d..9fc64e0a 100644
--- a/crates/lang/src/tipo/infer.rs
+++ b/crates/lang/src/tipo/infer.rs
@@ -6,6 +6,7 @@ use crate::{
         RecordConstructorArg, TypeAlias, TypedDefinition, TypedModule, UntypedDefinition,
         UntypedModule, Use,
     },
+    builtins,
     builtins::function,
     parser::token::Token,
     IdGenerator,
@@ -66,8 +67,8 @@ impl UntypedModule {
         for def in self.definitions().cloned() {
             match def {
                 Definition::ModuleConstant { .. } => consts.push(def),
-
                 Definition::Fn { .. }
+                | Definition::Test { .. }
                 | Definition::TypeAlias { .. }
                 | Definition::DataType { .. }
                 | Definition::Use { .. } => not_consts.push(def),
@@ -233,6 +234,17 @@ fn infer_definition(
             }))
         }
 
+        Definition::Test(f) => {
+            if let Definition::Fn(f) =
+                infer_definition(Definition::Fn(f), module_name, hydrators, environment)?
+            {
+                environment.unify(f.return_type.clone(), builtins::bool(), f.location)?;
+                Ok(Definition::Test(f))
+            } else {
+                unreachable!("test defintion inferred as something else than a function?")
+            }
+        }
+
         Definition::TypeAlias(TypeAlias {
             doc,
             location,
diff --git a/crates/project/src/error.rs b/crates/project/src/error.rs
index 46548e41..a1bc12f9 100644
--- a/crates/project/src/error.rs
+++ b/crates/project/src/error.rs
@@ -293,7 +293,7 @@ impl Diagnostic for Warning {
 
     fn code<'a>(&'a self) -> Option<Box<dyn Display + 'a>> {
         match self {
-            Warning::Type { .. } => Some(Box::new("aiken::typecheck")),
+            Warning::Type { .. } => Some(Box::new("aiken::check")),
         }
     }
 }
diff --git a/crates/project/src/lib.rs b/crates/project/src/lib.rs
index ab44c08d..59ce0be1 100644
--- a/crates/project/src/lib.rs
+++ b/crates/project/src/lib.rs
@@ -9,6 +9,7 @@ pub mod error;
 pub mod format;
 pub mod module;
 pub mod script;
+pub mod telemetry;
 
 use aiken_lang::{
     ast::{Definition, Function, ModuleKind, TypedFunction},
@@ -25,12 +26,17 @@ use pallas::{
 use pallas_traverse::ComputeHash;
 use script::Script;
 use serde_json::json;
-use uplc::ast::{DeBruijn, Program};
+use telemetry::{EventListener, TestInfo};
+use uplc::{
+    ast::{DeBruijn, Program},
+    machine::cost_model::ExBudget,
+};
 
 use crate::{
     config::Config,
     error::{Error, Warning},
     module::{CheckedModule, CheckedModules, ParsedModule, ParsedModules},
+    telemetry::Event,
 };
 
 #[derive(Debug)]
@@ -47,7 +53,10 @@ pub const MINT: &str = "mint";
 pub const WITHDRAWL: &str = "withdrawl";
 pub const VALIDATOR_NAMES: [&str; 4] = [SPEND, CERT, MINT, WITHDRAWL];
 
-pub struct Project {
+pub struct Project<T>
+where
+    T: EventListener,
+{
     config: Config,
     defined_modules: HashMap<String, PathBuf>,
     id_gen: IdGenerator,
@@ -55,10 +64,14 @@ pub struct Project {
     root: PathBuf,
     sources: Vec<Source>,
     pub warnings: Vec<Warning>,
+    event_listener: T,
 }
 
-impl Project {
-    pub fn new(config: Config, root: PathBuf) -> Project {
+impl<T> Project<T>
+where
+    T: EventListener,
+{
+    pub fn new(config: Config, root: PathBuf, event_listener: T) -> Project<T> {
         let id_gen = IdGenerator::new();
 
         let mut module_types = HashMap::new();
@@ -74,34 +87,60 @@ impl Project {
             root,
             sources: vec![],
             warnings: vec![],
+            event_listener,
         }
     }
 
     pub fn build(&mut self, uplc: bool) -> Result<(), Error> {
-        self.compile(true, uplc)
+        self.compile(true, uplc, false)
     }
 
-    pub fn check(&mut self) -> Result<(), Error> {
-        self.compile(false, false)
+    pub fn check(&mut self, skip_tests: bool) -> Result<(), Error> {
+        self.compile(false, false, !skip_tests)
     }
 
-    pub fn compile(&mut self, uplc_gen: bool, uplc_dump: bool) -> Result<(), Error> {
+    pub fn compile(
+        &mut self,
+        uplc_gen: bool,
+        uplc_dump: bool,
+        run_tests: bool,
+    ) -> Result<(), Error> {
+        self.event_listener
+            .handle_event(Event::StartingCompilation {
+                root: self.root.clone(),
+                name: self.config.name.clone(),
+                version: self.config.version.clone(),
+            });
+
+        self.event_listener.handle_event(Event::ParsingProjectFiles);
+
         self.read_source_files()?;
 
         let parsed_modules = self.parse_sources()?;
 
         let processing_sequence = parsed_modules.sequence()?;
 
+        self.event_listener.handle_event(Event::TypeChecking);
+
         let mut checked_modules = self.type_check(parsed_modules, processing_sequence)?;
 
         let validators = self.validate_validators(&mut checked_modules)?;
 
+        // TODO: In principle, uplc_gen and run_tests can't be true together. We probably want to
+        // model the options differently to make it obvious at the type-level.
         if uplc_gen {
+            self.event_listener.handle_event(Event::GeneratingUPLC {
+                output_path: self.output_path(),
+            });
             let programs = self.code_gen(validators, &checked_modules)?;
-
             self.write_build_outputs(programs, uplc_dump)?;
         }
 
+        if run_tests {
+            let tests = self.test_gen(&checked_modules)?;
+            self.run_tests(tests);
+        }
+
         Ok(())
     }
 
@@ -336,6 +375,7 @@ impl Project {
                             func,
                         );
                     }
+                    Definition::Test(_) => {}
                     Definition::TypeAlias(ta) => {
                         type_aliases.insert((module.name.clone(), ta.alias.clone()), ta);
                     }
@@ -385,11 +425,135 @@ impl Project {
         Ok(programs)
     }
 
-    fn write_build_outputs(&self, programs: Vec<Script>, uplc_dump: bool) -> Result<(), Error> {
-        let assets = self.root.join("assets");
+    // TODO: revisit ownership and lifetimes of data in this function
+    fn test_gen(&mut self, checked_modules: &CheckedModules) -> Result<Vec<Script>, Error> {
+        let mut programs = Vec::new();
+        let mut functions = HashMap::new();
+        let mut type_aliases = HashMap::new();
+        let mut data_types = HashMap::new();
+        let mut imports = HashMap::new();
+        let mut constants = HashMap::new();
 
+        // let mut indices_to_remove = Vec::new();
+        let mut tests = Vec::new();
+
+        for module in checked_modules.values() {
+            for (_index, def) in module.ast.definitions().enumerate() {
+                match def {
+                    Definition::Fn(func) => {
+                        functions.insert(
+                            FunctionAccessKey {
+                                module_name: module.name.clone(),
+                                function_name: func.name.clone(),
+                            },
+                            func,
+                        );
+                    }
+                    Definition::Test(func) => {
+                        tests.push((module.name.clone(), func));
+                        // indices_to_remove.push(index);
+                    }
+                    Definition::TypeAlias(ta) => {
+                        type_aliases.insert((module.name.clone(), ta.alias.clone()), ta);
+                    }
+                    Definition::DataType(dt) => {
+                        data_types.insert(
+                            DataTypeKey {
+                                module_name: module.name.clone(),
+                                defined_type: dt.name.clone(),
+                            },
+                            dt,
+                        );
+                    }
+                    Definition::Use(import) => {
+                        imports.insert((module.name.clone(), import.module.join("/")), import);
+                    }
+                    Definition::ModuleConstant(mc) => {
+                        constants.insert((module.name.clone(), mc.name.clone()), mc);
+                    }
+                }
+            }
+
+            // for index in indices_to_remove.drain(0..) {
+            //     module.ast.definitions.remove(index);
+            // }
+        }
+
+        for (module_name, func_def) in tests {
+            let Function {
+                arguments,
+                name,
+                body,
+                ..
+            } = func_def;
+
+            let mut generator = CodeGenerator::new(
+                &functions,
+                // &type_aliases,
+                &data_types,
+                // &imports,
+                // &constants,
+                &self.module_types,
+            );
+
+            let program = generator.generate(body.clone(), arguments.clone());
+
+            let script = Script::new(module_name, name.to_string(), program.try_into().unwrap());
+
+            programs.push(script);
+        }
+
+        Ok(programs)
+    }
+
+    fn run_tests(&self, tests: Vec<Script>) {
+        // TODO: in the future we probably just want to be able to
+        // tell the machine to not explode on budget consumption.
+        let initial_budget = ExBudget {
+            mem: i64::MAX,
+            cpu: i64::MAX,
+        };
+
+        if !tests.is_empty() {
+            self.event_listener.handle_event(Event::RunningTests);
+        }
+
+        let mut results = Vec::new();
+
+        for test in tests {
+            match test.program.eval(initial_budget) {
+                (Ok(..), remaining_budget, _) => {
+                    let test_info = TestInfo {
+                        is_passing: true,
+                        test,
+                        spent_budget: initial_budget - remaining_budget,
+                    };
+
+                    results.push(test_info);
+                }
+                (Err(_), remaining_budget, _) => {
+                    let test_info = TestInfo {
+                        is_passing: false,
+                        test,
+                        spent_budget: initial_budget - remaining_budget,
+                    };
+
+                    results.push(test_info);
+                }
+            }
+        }
+
+        self.event_listener
+            .handle_event(Event::FinishedTests { tests: results });
+    }
+
+    fn output_path(&self) -> PathBuf {
+        self.root.join("assets")
+    }
+
+    fn write_build_outputs(&self, programs: Vec<Script>, uplc_dump: bool) -> Result<(), Error> {
         for script in programs {
-            let script_output_dir = assets.join(script.module).join(script.name);
+            let script_output_dir = self.output_path().join(script.module).join(script.name);
 
             fs::create_dir_all(&script_output_dir)?;
 
diff --git a/crates/project/src/telemetry.rs b/crates/project/src/telemetry.rs
new file mode 100644
index 00000000..4bc8da61
--- /dev/null
+++ b/crates/project/src/telemetry.rs
@@ -0,0 +1,30 @@
+use crate::script::Script;
+use std::path::PathBuf;
+use uplc::machine::cost_model::ExBudget;
+
+pub trait EventListener: std::fmt::Debug {
+    fn handle_event(&self, event: Event);
+}
+
+pub enum Event {
+    StartingCompilation {
+        name: String,
+        version: String,
+        root: PathBuf,
+    },
+    ParsingProjectFiles,
+    TypeChecking,
+    GeneratingUPLC {
+        output_path: PathBuf,
+    },
+    RunningTests,
+    FinishedTests {
+        tests: Vec<TestInfo>,
+    },
+}
+
+pub struct TestInfo {
+    pub is_passing: bool,
+    pub test: Script,
+    pub spent_budget: ExBudget,
+}
diff --git a/crates/uplc/src/ast.rs b/crates/uplc/src/ast.rs
index d8019604..8306e1e7 100644
--- a/crates/uplc/src/ast.rs
+++ b/crates/uplc/src/ast.rs
@@ -495,6 +495,7 @@ impl From<Term<FakeNamedDeBruijn>> for Term<NamedDeBruijn> {
 impl Program<NamedDeBruijn> {
     pub fn eval(
         &self,
+        initial_budget: ExBudget,
     ) -> (
         Result<Term<NamedDeBruijn>, crate::machine::Error>,
         ExBudget,
@@ -503,7 +504,7 @@ impl Program<NamedDeBruijn> {
         let mut machine = Machine::new(
             Language::PlutusV2,
             CostModel::default(),
-            ExBudget::default(),
+            initial_budget,
             200,
         );
 
@@ -558,6 +559,7 @@ impl Program<NamedDeBruijn> {
 impl Program<DeBruijn> {
     pub fn eval(
         &self,
+        initial_budget: ExBudget,
     ) -> (
         Result<Term<NamedDeBruijn>, crate::machine::Error>,
         ExBudget,
@@ -565,7 +567,7 @@ impl Program<DeBruijn> {
     ) {
         let program: Program<NamedDeBruijn> = self.clone().into();
 
-        program.eval()
+        program.eval(initial_budget)
     }
 }
 
diff --git a/crates/uplc/src/machine/cost_model.rs b/crates/uplc/src/machine/cost_model.rs
index 98be17e7..0131d0e1 100644
--- a/crates/uplc/src/machine/cost_model.rs
+++ b/crates/uplc/src/machine/cost_model.rs
@@ -47,6 +47,17 @@ impl Default for ExBudget {
     }
 }
 
+impl std::ops::Sub for ExBudget {
+    type Output = Self;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        ExBudget {
+            mem: self.mem - rhs.mem,
+            cpu: self.cpu - rhs.cpu,
+        }
+    }
+}
+
 #[derive(Default)]
 pub struct CostModel {
     pub machine_costs: MachineCosts,
diff --git a/crates/uplc/src/tx/eval.rs b/crates/uplc/src/tx/eval.rs
index 9684c8e3..2c08f0bb 100644
--- a/crates/uplc/src/tx/eval.rs
+++ b/crates/uplc/src/tx/eval.rs
@@ -786,7 +786,7 @@ pub fn eval_redeemer(
 
                         program.eval_as(&Language::PlutusV2, costs, initial_budget)
                     } else {
-                        program.eval()
+                        program.eval(ExBudget::default())
                     };
 
                     match result {
@@ -889,7 +889,7 @@ pub fn eval_redeemer(
 
                         program.eval_as(&Language::PlutusV2, costs, initial_budget)
                     } else {
-                        program.eval()
+                        program.eval(ExBudget::default())
                     };
 
                     match result {
diff --git a/examples/sample/lib/sample/thing.ak b/examples/sample/lib/sample/thing.ak
new file mode 100644
index 00000000..503d6da2
--- /dev/null
+++ b/examples/sample/lib/sample/thing.ak
@@ -0,0 +1,5 @@
+use aiken/builtin
+
+test bar() {
+  builtin.length_of_bytearray(#[2, 2, 3]) == 3
+}
diff --git a/examples/sample/validators/swap.ak b/examples/sample/validators/swap.ak
index e1bc32b2..aedd877e 100644
--- a/examples/sample/validators/swap.ak
+++ b/examples/sample/validators/swap.ak
@@ -1,7 +1,7 @@
 use sample
 
 pub fn spend(datum: sample.Datum, rdmr: sample.Redeemer, _ctx: Nil) -> Bool {
-  let x = #(datum,  #[244])
+  let _x = #(datum, rdmr, #[244])
 
   let y = [#(#[222], #[222]), #(#[233], #[52])]
 
@@ -11,3 +11,7 @@ pub fn spend(datum: sample.Datum, rdmr: sample.Redeemer, _ctx: Nil) -> Bool {
 
   z == #(#[222], #[222])
 }
+
+test foo() {
+  1 + 1 == 2
+}