diff --git a/src/ast/mod.rs b/src/ast/mod.rs
index 493a30b..7d552b8 100644
--- a/src/ast/mod.rs
+++ b/src/ast/mod.rs
@@ -16,6 +16,7 @@ use either::Either;
 use pest::Span;
 
 mod parser;
+mod tests;
 
 pub trait Node<'i> {
     fn as_node(&self) -> &dyn Node<'i>;
@@ -34,6 +35,10 @@ pub trait Node<'i> {
         None
     }
 
+    fn as_error(&self) -> Option<&ErrorStatement<'i>> {
+        None
+    }
+
     fn identifiers<'n>(&'n self) -> FilterWalk<'i, 'n, Identifier<'i>> {
         FilterWalk::new(self.as_node(), |node| node.as_identifier())
     }
@@ -41,6 +46,10 @@ pub trait Node<'i> {
     fn strings<'n>(&'n self) -> FilterWalk<'i, 'n, StringLiteral<'i>> {
         FilterWalk::new(self.as_node(), |node| node.as_string())
     }
+
+    fn errors<'n>(&'n self) -> FilterWalk<'i, 'n, ErrorStatement<'i>> {
+        FilterWalk::new(self.as_node(), |node| node.as_error())
+    }
 }
 
 pub struct Walk<'i, 'n> {
@@ -594,6 +603,10 @@ impl<'i> Node<'i> for ErrorStatement<'i> {
         self
     }
 
+    fn as_error(&self) -> Option<&ErrorStatement<'i>> {
+        Some(self)
+    }
+
     fn children(&self) -> Vec<&dyn Node<'i>> {
         match self {
             ErrorStatement::UnknownStatement(unknown) => vec![unknown.as_node()],
diff --git a/src/ast/parser.rs b/src/ast/parser.rs
index 2255563..a8ae307 100644
--- a/src/ast/parser.rs
+++ b/src/ast/parser.rs
@@ -352,77 +352,3 @@ pub fn parse(input: &str) -> Block {
         .unwrap();
     convert_file(file_pair)
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn smoke() {
-        // Empty
-        parse("");
-        parse(" \r\n\t");
-
-        // Assignment
-        parse("a = 1");
-        parse("a += 1");
-        parse("a -= 1");
-        parse("a[1] = 1");
-        parse("a.b = 1");
-
-        // Conditional
-        parse("if (true) {}");
-        parse("if (true) { a = 1 }");
-        parse("if (true) {} else {}");
-        parse("if (true) { a = 1 } else { a = 2 }");
-        parse("if (true) {} else if (true) {}");
-        parse("if (true) { a = 1 } else if (true) { a = 2 }");
-        parse("if (true) {} else if (true) {} else {}");
-        parse("if (true) { a = 1 } else if (true) { a = 2 } else { a = 3 }");
-
-        // Call
-        parse("assert(true)");
-        parse("declare_args() {}");
-        parse("declare_args() { a = 1 }");
-        parse("template(\"foo\") {}");
-        parse("template(\"foo\") { bar(target_name) }");
-
-        // Expressions
-        parse("a = 1");
-        parse("a = b[1]");
-        parse("a = b.c");
-        parse("a = 1 + 2 * 3");
-        parse("a = 1 == 2");
-        parse("a = 1 <= 2");
-        parse("a = true && false || !false");
-        parse(r#"a = "foo\"bar\\baz""#);
-        parse("a = b(c)");
-        parse("a = b.c");
-        parse("a = {}");
-        parse("a = { b = 1 }");
-        parse("a = (((1)))");
-        parse("a = []");
-        parse("a = [1]");
-        parse("a = [1, ]");
-        parse("a = [1, 2]");
-        parse("a = [1, 2, ]");
-
-        // TODO: Add more tests.
-    }
-
-    #[test]
-    fn comments() {
-        parse("# comment");
-        parse("# comment\n  # comment\n");
-        parse("a = 1 # comment");
-    }
-
-    #[test]
-    fn error_recovery() {
-        parse("a = 1 2 3");
-        parse("a = \"foo\nb = 1");
-        parse("declare_args() {}}");
-
-        // TODO: Add more tests.
-    }
-}
diff --git a/src/ast/tests.rs b/src/ast/tests.rs
new file mode 100644
index 0000000..c3887fe
--- /dev/null
+++ b/src/ast/tests.rs
@@ -0,0 +1,97 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#![cfg(test)]
+
+use super::{parse, Node};
+
+fn parse_no_errors(input: &str) {
+    let block = parse(input);
+    let errors: Vec<_> = block.errors().collect();
+    assert!(
+        errors.is_empty(),
+        "parse failed!\n\tinput = {:?}\n\terrors = {:?}",
+        input,
+        errors
+    );
+}
+
+#[test]
+fn smoke() {
+    // Empty
+    parse_no_errors("");
+    parse_no_errors(" \r\n\t");
+
+    // Assignment
+    parse_no_errors("a = 1");
+    parse_no_errors("a += 1");
+    parse_no_errors("a -= 1");
+    parse_no_errors("a[1] = 1");
+    parse_no_errors("a.b = 1");
+
+    // Conditional
+    parse_no_errors("if (true) {}");
+    parse_no_errors("if (true) { a = 1 }");
+    parse_no_errors("if (true) {} else {}");
+    parse_no_errors("if (true) { a = 1 } else { a = 2 }");
+    parse_no_errors("if (true) {} else if (true) {}");
+    parse_no_errors("if (true) { a = 1 } else if (true) { a = 2 }");
+    parse_no_errors("if (true) {} else if (true) {} else {}");
+    parse_no_errors("if (true) { a = 1 } else if (true) { a = 2 } else { a = 3 }");
+
+    // Call
+    parse_no_errors("assert(true)");
+    parse_no_errors("declare_args() {}");
+    parse_no_errors("declare_args() { a = 1 }");
+    parse_no_errors("template(\"foo\") {}");
+    parse_no_errors("template(\"foo\") { bar(target_name) }");
+
+    // Expressions
+    parse_no_errors("a = 1");
+    parse_no_errors("a = b[1]");
+    parse_no_errors("a = b.c");
+    parse_no_errors("a = 1 + 2 - 3");
+    parse_no_errors("a = 1 == 2");
+    parse_no_errors("a = 1 <= 2");
+    parse_no_errors("a = true && false || !false");
+    parse_no_errors(r#"a = "foo\"bar\\baz""#);
+    parse_no_errors("a = b(c)");
+    parse_no_errors("a = b.c");
+    parse_no_errors("a = {}");
+    parse_no_errors("a = { b = 1 }");
+    parse_no_errors("a = (((1)))");
+    parse_no_errors("a = []");
+    parse_no_errors("a = [1]");
+    parse_no_errors("a = [1, ]");
+    parse_no_errors("a = [1, 2]");
+    parse_no_errors("a = [1, 2, ]");
+
+    // TODO: Add more tests.
+}
+
+#[test]
+fn comments() {
+    parse_no_errors("# comment");
+    parse_no_errors("# comment\n  # comment\n");
+    parse_no_errors("a = 1 # comment");
+}
+
+#[test]
+fn error_recovery() {
+    parse("a = 1 2 3");
+    parse("a = \"foo\nb = 1");
+    parse("declare_args() {}}");
+
+    // TODO: Add more tests.
+}