diff --git a/crates/aiken-lang/src/ast.rs b/crates/aiken-lang/src/ast.rs
index 4487e7b0..6c9f0d49 100644
--- a/crates/aiken-lang/src/ast.rs
+++ b/crates/aiken-lang/src/ast.rs
@@ -118,7 +118,6 @@ fn str_to_keyword(word: &str) -> Option<Token> {
         "test" => Some(Token::Test),
         "error" => Some(Token::ErrorTerm),
         "validator" => Some(Token::Validator),
-        "fail" => Some(Token::Fail),
         _ => None,
     }
 }
diff --git a/crates/aiken-lang/src/format.rs b/crates/aiken-lang/src/format.rs
index 8f94dcdd..5c91ca83 100644
--- a/crates/aiken-lang/src/format.rs
+++ b/crates/aiken-lang/src/format.rs
@@ -251,8 +251,17 @@ impl<'comments> Formatter<'comments> {
                 arguments: args,
                 body,
                 end_position,
+                can_error,
                 ..
-            }) => self.definition_fn(&false, "test", name, args, &None, body, *end_position),
+            }) => self.definition_fn(
+                &false,
+                if *can_error { "!test" } else { "test" },
+                name,
+                args,
+                &None,
+                body,
+                *end_position,
+            ),
 
             Definition::TypeAlias(TypeAlias {
                 alias,
diff --git a/crates/aiken-lang/src/parser.rs b/crates/aiken-lang/src/parser.rs
index 9ac01e75..a639234f 100644
--- a/crates/aiken-lang/src/parser.rs
+++ b/crates/aiken-lang/src/parser.rs
@@ -337,8 +337,10 @@ 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(just(Token::Fail).ignored().or_not())
+    just(Token::Bang)
+        .ignored()
+        .or_not()
+        .then_ignore(just(Token::Test))
         .then(select! {Token::Name {name} => name})
         .then_ignore(just(Token::LeftParen))
         .then_ignore(just(Token::RightParen))
diff --git a/crates/aiken-lang/src/parser/lexer.rs b/crates/aiken-lang/src/parser/lexer.rs
index 37058e41..3587c37f 100644
--- a/crates/aiken-lang/src/parser/lexer.rs
+++ b/crates/aiken-lang/src/parser/lexer.rs
@@ -115,7 +115,6 @@ pub fn lexer() -> impl Parser<char, Vec<(Token, Span)>, Error = ParseError> {
         "todo" => Token::Todo,
         "type" => Token::Type,
         "when" => Token::When,
-        "fail" => Token::Fail,
         "validator" => Token::Validator,
         _ => {
             if s.chars().next().map_or(false, |c| c.is_uppercase()) {
diff --git a/crates/aiken-lang/src/parser/token.rs b/crates/aiken-lang/src/parser/token.rs
index 1fe4418b..b06a4783 100644
--- a/crates/aiken-lang/src/parser/token.rs
+++ b/crates/aiken-lang/src/parser/token.rs
@@ -80,7 +80,6 @@ pub enum Token {
     When,
     Trace,
     Validator,
-    Fail,
 }
 
 impl fmt::Display for Token {
@@ -165,7 +164,6 @@ impl fmt::Display for Token {
             Token::Test => "test",
             Token::ErrorTerm => "error",
             Token::Validator => "validator",
-            Token::Fail => "fail",
         };
         write!(f, "\"{s}\"")
     }
diff --git a/crates/aiken-lang/src/tests/format.rs b/crates/aiken-lang/src/tests/format.rs
index 5fa5e6eb..7c488d1d 100644
--- a/crates/aiken-lang/src/tests/format.rs
+++ b/crates/aiken-lang/src/tests/format.rs
@@ -786,3 +786,16 @@ fn match_record() {
 
     assert_fmt(src, src);
 }
+
+#[test]
+fn test_fail() {
+    let src = indoc! { r#"
+      !test foo() {
+        expect Some(a) = bar
+
+        a
+      }
+    "#};
+
+    assert_fmt(src, src);
+}
diff --git a/crates/aiken-lang/src/tests/parser.rs b/crates/aiken-lang/src/tests/parser.rs
index b2a0b4de..c3bd9a36 100644
--- a/crates/aiken-lang/src/tests/parser.rs
+++ b/crates/aiken-lang/src/tests/parser.rs
@@ -41,7 +41,7 @@ fn windows_newline() {
 #[test]
 fn test_fail() {
     let code = indoc! {r#"
-       test fail invalid_inputs() {
+       !test invalid_inputs() {
          expect True = False
 
          False
@@ -53,17 +53,17 @@ fn test_fail() {
         vec![ast::UntypedDefinition::Test(ast::Function {
             arguments: vec![],
             body: expr::UntypedExpr::Sequence {
-                location: Span::new((), 31..59),
+                location: Span::new((), 27..55),
                 expressions: vec![
                     expr::UntypedExpr::Assignment {
-                        location: Span::new((), 31..50),
+                        location: Span::new((), 27..46),
                         value: Box::new(expr::UntypedExpr::Var {
-                            location: Span::new((), 45..50),
+                            location: Span::new((), 41..46),
                             name: "False".to_string(),
                         }),
                         pattern: ast::UntypedPattern::Constructor {
                             is_record: false,
-                            location: Span::new((), 38..42),
+                            location: Span::new((), 34..38),
                             name: "True".to_string(),
                             arguments: vec![],
                             module: None,
@@ -75,18 +75,18 @@ fn test_fail() {
                         annotation: None,
                     },
                     expr::UntypedExpr::Var {
-                        location: Span::new((), 54..59),
+                        location: Span::new((), 50..55),
                         name: "False".to_string(),
                     },
                 ],
             },
             doc: None,
-            location: Span::new((), 0..26),
+            location: Span::new((), 0..22),
             name: "invalid_inputs".to_string(),
             public: false,
             return_annotation: None,
             return_type: (),
-            end_position: 60,
+            end_position: 56,
             can_error: true,
         })],
     );