diff --git a/cli/src/generate/prepare_grammar/intern_symbols.rs b/cli/src/generate/prepare_grammar/intern_symbols.rs
index a466935b..a7248817 100644
--- a/cli/src/generate/prepare_grammar/intern_symbols.rs
+++ b/cli/src/generate/prepare_grammar/intern_symbols.rs
@@ -219,7 +219,7 @@ mod tests {
         let result = intern_symbols(&build_grammar(vec![Variable::named("x", Rule::named("y"))]));
 
         match result {
-            Err(Error(message)) => assert_eq!(message, "Undefined symbol 'y'"),
+            Err(Error(message)) => assert_eq!(message, "Undefined symbol `y`"),
             _ => panic!("Expected an error but got none"),
         }
     }
diff --git a/cli/src/generate/prepare_grammar/process_inlines.rs b/cli/src/generate/prepare_grammar/process_inlines.rs
index 3c0f529a..f58de63d 100644
--- a/cli/src/generate/prepare_grammar/process_inlines.rs
+++ b/cli/src/generate/prepare_grammar/process_inlines.rs
@@ -408,7 +408,7 @@ mod tests {
                             ProductionStep::new(Symbol::terminal(11))
                                 .with_prec(2, None)
                                 .with_alias("inner_alias", true),
-                            ProductionStep::new(Symbol::terminal(12)).with_prec(3, None),
+                            ProductionStep::new(Symbol::terminal(12)),
                         ],
                     }],
                 },
diff --git a/cli/src/generate/properties.rs b/cli/src/generate/properties.rs
index 9e570a99..e3b60185 100644
--- a/cli/src/generate/properties.rs
+++ b/cli/src/generate/properties.rs
@@ -118,7 +118,7 @@ impl Builder {
         self.remove_duplicate_states();
 
         for (i, state) in self.output.states.iter_mut().enumerate() {
-            state.id = i;
+            state.id = Some(i);
         }
 
         self.output
@@ -130,7 +130,7 @@ impl Builder {
             Entry::Vacant(v) => {
                 let state_id = self.output.states.len();
                 self.output.states.push(PropertyStateJSON {
-                    id: 0,
+                    id: None,
                     transitions: Vec::new(),
                     property_set_id: 0,
                     default_next_state_id: 0,
diff --git a/cli/src/main.rs b/cli/src/main.rs
index 334f06ef..9f095668 100644
--- a/cli/src/main.rs
+++ b/cli/src/main.rs
@@ -17,6 +17,9 @@ mod parse;
 mod test;
 mod util;
 
+#[cfg(test)]
+mod tests;
+
 use self::loader::Loader;
 use clap::{App, Arg, SubCommand};
 use std::env;
diff --git a/cli/src/tests/corpuses.rs b/cli/src/tests/corpuses.rs
new file mode 100644
index 00000000..b70bb371
--- /dev/null
+++ b/cli/src/tests/corpuses.rs
@@ -0,0 +1,57 @@
+use super::languages;
+use crate::test::{parse_tests, TestEntry};
+use std::path::PathBuf;
+use tree_sitter::{Language, Parser};
+
+lazy_static! {
+    static ref LANGUAGES: [(&'static str, Language); 6] = [
+        ("c", languages::c()),
+        ("cpp", languages::cpp()),
+        ("embedded-template", languages::embedded_template()),
+        ("go", languages::go()),
+        ("html", languages::html()),
+        ("javascript", languages::javascript()),
+    ];
+}
+
+#[test]
+fn test_corpus_files() {
+    let mut parser = Parser::new();
+    let grammars_dir: PathBuf = [
+        env!("CARGO_MANIFEST_DIR"),
+        "..",
+        "test",
+        "fixtures",
+        "grammars",
+    ]
+    .iter()
+    .collect();
+
+    for (name, language) in LANGUAGES.iter().cloned() {
+        let corpus_dir = grammars_dir.join(name).join("corpus");
+        let test = parse_tests(&corpus_dir).unwrap();
+        parser.set_language(language).unwrap();
+        run_mutation_tests(&mut parser, test);
+    }
+}
+
+fn run_mutation_tests(parser: &mut Parser, test: TestEntry) {
+    match test {
+        TestEntry::Example {
+            name,
+            input,
+            output,
+        } => {
+            let tree = parser
+                .parse_utf8(&mut |byte_offset, _| &input[byte_offset..], None)
+                .unwrap();
+            let actual = tree.root_node().to_sexp();
+            assert_eq!(actual, output);
+        }
+        TestEntry::Group { name, children } => {
+            for child in children {
+                run_mutation_tests(parser, child);
+            }
+        }
+    }
+}
diff --git a/cli/src/tests/languages.rs b/cli/src/tests/languages.rs
new file mode 100644
index 00000000..0c483d08
--- /dev/null
+++ b/cli/src/tests/languages.rs
@@ -0,0 +1,19 @@
+use tree_sitter::Language;
+
+extern "C" {
+    fn tree_sitter_c() -> Language;
+    fn tree_sitter_cpp() -> Language;
+    fn tree_sitter_embedded_template() -> Language;
+    fn tree_sitter_go() -> Language;
+    fn tree_sitter_html() -> Language;
+    fn tree_sitter_javascript() -> Language;
+    fn tree_sitter_rust() -> Language;
+}
+
+pub fn c() -> Language { unsafe { tree_sitter_c() } }
+pub fn cpp() -> Language { unsafe { tree_sitter_cpp() } }
+pub fn embedded_template() -> Language { unsafe { tree_sitter_embedded_template() } }
+pub fn go() -> Language { unsafe { tree_sitter_go() } }
+pub fn html() -> Language { unsafe { tree_sitter_html() } }
+pub fn javascript() -> Language { unsafe { tree_sitter_javascript() } }
+pub fn rust() -> Language { unsafe { tree_sitter_rust() } }
diff --git a/cli/src/tests/mod.rs b/cli/src/tests/mod.rs
new file mode 100644
index 00000000..bc199616
--- /dev/null
+++ b/cli/src/tests/mod.rs
@@ -0,0 +1,3 @@
+mod languages;
+mod corpuses;
+mod parser_api;
diff --git a/cli/src/tests/parser_api.rs b/cli/src/tests/parser_api.rs
new file mode 100644
index 00000000..af5ba71f
--- /dev/null
+++ b/cli/src/tests/parser_api.rs
@@ -0,0 +1,507 @@
+use super::languages::rust;
+use std::thread;
+use tree_sitter::{InputEdit, LogType, Parser, Point, PropertySheet, Range};
+
+#[test]
+fn test_basic_parsing() {
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+
+    let tree = parser
+        .parse_str(
+            "
+        struct Stuff {}
+        fn main() {}
+    ",
+            None,
+        )
+        .unwrap();
+
+    let root_node = tree.root_node();
+    assert_eq!(root_node.kind(), "source_file");
+
+    assert_eq!(
+        root_node.to_sexp(),
+        "(source_file (struct_item (type_identifier) (field_declaration_list)) (function_item (identifier) (parameters) (block)))"
+    );
+
+    let struct_node = root_node.child(0).unwrap();
+    assert_eq!(struct_node.kind(), "struct_item");
+}
+
+#[test]
+fn test_logging() {
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+
+    let mut messages = Vec::new();
+    parser.set_logger(Some(Box::new(|log_type, message| {
+        messages.push((log_type, message.to_string()));
+    })));
+
+    parser
+        .parse_str(
+            "
+        struct Stuff {}
+        fn main() {}
+    ",
+            None,
+        )
+        .unwrap();
+
+    assert!(messages.contains(&(
+        LogType::Parse,
+        "reduce sym:struct_item, child_count:3".to_string()
+    )));
+    assert!(messages.contains(&(LogType::Lex, "skip character:' '".to_string())));
+}
+
+#[test]
+fn test_tree_cursor() {
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+
+    let tree = parser
+        .parse_str(
+            "
+                struct Stuff {
+                    a: A;
+                    b: Option<B>,
+                }
+            ",
+            None,
+        )
+        .unwrap();
+
+    let mut cursor = tree.walk();
+    assert_eq!(cursor.node().kind(), "source_file");
+
+    assert!(cursor.goto_first_child());
+    assert_eq!(cursor.node().kind(), "struct_item");
+
+    assert!(cursor.goto_first_child());
+    assert_eq!(cursor.node().kind(), "struct");
+    assert_eq!(cursor.node().is_named(), false);
+
+    assert!(cursor.goto_next_sibling());
+    assert_eq!(cursor.node().kind(), "type_identifier");
+    assert_eq!(cursor.node().is_named(), true);
+
+    assert!(cursor.goto_next_sibling());
+    assert_eq!(cursor.node().kind(), "field_declaration_list");
+    assert_eq!(cursor.node().is_named(), true);
+}
+
+#[test]
+fn test_tree_property_matching() {
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+    let source_code = "fn f1() { f2(); }";
+    let tree = parser.parse_str(source_code, None).unwrap();
+
+    #[derive(Debug, Deserialize, PartialEq, Eq)]
+    struct Properties {
+        reference: Option<String>,
+        define: Option<String>,
+    }
+
+    let empty_properties = Properties {
+        reference: None,
+        define: None,
+    };
+
+    let property_sheet = PropertySheet::<Properties>::new(
+        rust(),
+        r##"
+        {
+            "states": [
+                {
+                    "transitions": [
+                        {"type": "call_expression", "named": true, "state_id": 1},
+                        {"type": "function_item", "named": true, "state_id": 2}
+                    ],
+                    "default_next_state_id": 0,
+                    "property_set_id": 0
+                },
+                {
+                    "transitions": [
+                        {"type": "identifier", "named": true, "state_id": 3}
+                    ],
+                    "default_next_state_id": 0,
+                    "property_set_id": 0
+                },
+                {
+                    "transitions": [
+                        {"type": "identifier", "named": true, "state_id": 4}
+                    ],
+                    "default_next_state_id": 0,
+                    "property_set_id": 0
+                },
+                {
+                    "transitions": [],
+                    "default_next_state_id": 0,
+                    "property_set_id": 1
+                },
+                {
+                    "transitions": [],
+                    "default_next_state_id": 0,
+                    "property_set_id": 2
+                }
+            ],
+            "property_sets": [
+                {},
+                {"reference": "function"},
+                {"define": "function"}
+            ]
+        }
+    "##,
+    )
+    .unwrap();
+
+    let mut cursor = tree.walk_with_properties(&property_sheet, source_code);
+    assert_eq!(cursor.node().kind(), "source_file");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+
+    assert!(cursor.goto_first_child());
+    assert_eq!(cursor.node().kind(), "function_item");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+
+    assert!(cursor.goto_first_child());
+    assert_eq!(cursor.node().kind(), "fn");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+    assert!(!cursor.goto_first_child());
+
+    assert!(cursor.goto_next_sibling());
+    assert_eq!(cursor.node().kind(), "identifier");
+    assert_eq!(cursor.node_properties().define, Some("function".to_owned()));
+    assert!(!cursor.goto_first_child());
+
+    assert!(cursor.goto_next_sibling());
+    assert_eq!(cursor.node().kind(), "parameters");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+
+    assert!(cursor.goto_first_child());
+    assert_eq!(cursor.node().kind(), "(");
+    assert!(cursor.goto_next_sibling());
+    assert_eq!(cursor.node().kind(), ")");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+
+    assert!(cursor.goto_parent());
+    assert!(cursor.goto_next_sibling());
+    assert_eq!(cursor.node().kind(), "block");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+
+    assert!(cursor.goto_first_child());
+    assert!(cursor.goto_next_sibling());
+    assert_eq!(cursor.node().kind(), "call_expression");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+
+    assert!(cursor.goto_first_child());
+    assert_eq!(cursor.node().kind(), "identifier");
+    assert_eq!(
+        cursor.node_properties().reference,
+        Some("function".to_owned())
+    );
+}
+
+#[test]
+fn test_tree_property_matching_with_regexes() {
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+    let source_code = "fn f1() { None(a()) }";
+    let tree = parser.parse_str(source_code, None).unwrap();
+
+    #[derive(Debug, Deserialize, PartialEq, Eq)]
+    struct Properties {
+        scope: Option<String>,
+    }
+
+    let empty_properties = Properties { scope: None };
+
+    let property_sheet = PropertySheet::<Properties>::new(
+        rust(),
+        r##"
+        {
+            "states": [
+                {
+                    "id": 0,
+                    "transitions": [
+                        {"type": "call_expression", "named": true, "state_id": 1}
+                    ],
+                    "default_next_state_id": 0,
+                    "property_set_id": 0
+                },
+                {
+                    "id": 1,
+                    "transitions": [
+                        {"type": "identifier", "named": true, "text": "^[A-Z]", "state_id": 2},
+                        {"type": "identifier", "named": true, "state_id": 3}
+                    ],
+                    "default_next_state_id": 0,
+                    "property_set_id": 0
+                },
+                {
+                    "transitions": [],
+                    "default_next_state_id": 0,
+                    "property_set_id": 1
+                },
+                {
+                    "transitions": [],
+                    "default_next_state_id": 0,
+                    "property_set_id": 2
+                }
+            ],
+            "property_sets": [
+                {},
+                {"scope": "constructor"},
+                {"scope": "function"}
+            ]
+        }
+    "##,
+    )
+    .unwrap();
+
+    let mut cursor = tree.walk_with_properties(&property_sheet, source_code);
+    assert_eq!(cursor.node().kind(), "source_file");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+
+    cursor.goto_first_child();
+    assert!(cursor.goto_first_child());
+    assert!(cursor.goto_next_sibling());
+    assert!(cursor.goto_next_sibling());
+    assert!(cursor.goto_next_sibling());
+    assert_eq!(cursor.node().kind(), "block");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+
+    assert!(cursor.goto_first_child());
+    assert!(cursor.goto_next_sibling());
+    assert_eq!(cursor.node().kind(), "call_expression");
+    assert_eq!(*cursor.node_properties(), empty_properties);
+
+    assert!(cursor.goto_first_child());
+    assert_eq!(cursor.node().kind(), "identifier");
+    assert_eq!(
+        cursor.node_properties().scope,
+        Some("constructor".to_owned())
+    );
+}
+
+#[test]
+fn test_custom_utf8_input() {
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+
+    let lines = &["pub fn foo() {", "  1", "}"];
+
+    let tree = parser
+        .parse_utf8(
+            &mut |_, position| {
+                let row = position.row;
+                let column = position.column;
+                if row < lines.len() {
+                    if column < lines[row].as_bytes().len() {
+                        &lines[row].as_bytes()[column..]
+                    } else {
+                        "\n".as_bytes()
+                    }
+                } else {
+                    &[]
+                }
+            },
+            None,
+        )
+        .unwrap();
+
+    let root = tree.root_node();
+    assert_eq!(root.to_sexp(), "(source_file (function_item (visibility_modifier) (identifier) (parameters) (block (integer_literal))))");
+    assert_eq!(root.kind(), "source_file");
+    assert_eq!(root.has_error(), false);
+    assert_eq!(root.child(0).unwrap().kind(), "function_item");
+}
+
+#[test]
+fn test_custom_utf16_input() {
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+
+    parser.set_logger(Some(Box::new(|t, message| {
+        println!("log: {:?} {}", t, message);
+    })));
+
+    let lines: Vec<Vec<u16>> = ["pub fn foo() {", "  1", "}"]
+        .iter()
+        .map(|s| s.encode_utf16().collect())
+        .collect();
+
+    let tree = parser
+        .parse_utf16(
+            &mut |_, position| {
+                let row = position.row;
+                let column = position.column;
+                if row < lines.len() {
+                    if column < lines[row].len() {
+                        &lines[row][column..]
+                    } else {
+                        &[10]
+                    }
+                } else {
+                    &[]
+                }
+            },
+            None,
+        )
+        .unwrap();
+
+    let root = tree.root_node();
+    assert_eq!(root.to_sexp(), "(source_file (function_item (visibility_modifier) (identifier) (parameters) (block (integer_literal))))");
+    assert_eq!(root.kind(), "source_file");
+    assert_eq!(root.has_error(), false);
+    assert_eq!(root.child(0).unwrap().kind(), "function_item");
+}
+
+#[test]
+fn test_node_equality() {
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+    let tree = parser.parse_str("struct A {}", None).unwrap();
+    let node1 = tree.root_node();
+    let node2 = tree.root_node();
+    assert_eq!(node1, node2);
+    assert_eq!(node1.child(0).unwrap(), node2.child(0).unwrap());
+    assert_ne!(node1.child(0).unwrap(), node2);
+}
+
+#[test]
+fn test_editing() {
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+
+    let mut input_bytes = "fn test(a: A, c: C) {}".as_bytes();
+    let mut input_bytes_read = Vec::new();
+
+    let mut tree = parser
+        .parse_utf8(
+            &mut |offset, _| {
+                let offset = offset;
+                if offset < input_bytes.len() {
+                    let result = &input_bytes[offset..offset + 1];
+                    input_bytes_read.extend(result.iter());
+                    result
+                } else {
+                    &[]
+                }
+            },
+            None,
+        )
+        .unwrap();
+
+    let parameters_sexp = tree
+        .root_node()
+        .named_child(0)
+        .unwrap()
+        .named_child(1)
+        .unwrap()
+        .to_sexp();
+    assert_eq!(
+        parameters_sexp,
+        "(parameters (parameter (identifier) (type_identifier)) (parameter (identifier) (type_identifier)))"
+    );
+
+    input_bytes_read.clear();
+    input_bytes = "fn test(a: A, b: B, c: C) {}".as_bytes();
+    tree.edit(&InputEdit {
+        start_byte: 14,
+        old_end_byte: 14,
+        new_end_byte: 20,
+        start_position: Point::new(0, 14),
+        old_end_position: Point::new(0, 14),
+        new_end_position: Point::new(0, 20),
+    });
+
+    let tree = parser
+        .parse_utf8(
+            &mut |offset, _| {
+                let offset = offset;
+                if offset < input_bytes.len() {
+                    let result = &input_bytes[offset..offset + 1];
+                    input_bytes_read.extend(result.iter());
+                    result
+                } else {
+                    &[]
+                }
+            },
+            Some(&tree),
+        )
+        .unwrap();
+
+    let parameters_sexp = tree
+        .root_node()
+        .named_child(0)
+        .unwrap()
+        .named_child(1)
+        .unwrap()
+        .to_sexp();
+    assert_eq!(
+        parameters_sexp,
+        "(parameters (parameter (identifier) (type_identifier)) (parameter (identifier) (type_identifier)) (parameter (identifier) (type_identifier)))"
+    );
+
+    let retokenized_content = String::from_utf8(input_bytes_read).unwrap();
+    assert!(retokenized_content.contains("b: B"));
+    assert!(!retokenized_content.contains("a: A"));
+    assert!(!retokenized_content.contains("c: C"));
+    assert!(!retokenized_content.contains("{}"));
+}
+
+#[test]
+fn test_parallel_parsing() {
+    // Parse this source file so that each thread has a non-trivial amount of
+    // work to do.
+    let this_file_source = include_str!("parser_api.rs");
+
+    let mut parser = Parser::new();
+    parser.set_language(rust()).unwrap();
+    let tree = parser.parse_str(this_file_source, None).unwrap();
+
+    let mut parse_threads = Vec::new();
+    for thread_id in 1..5 {
+        let mut tree_clone = tree.clone();
+        parse_threads.push(thread::spawn(move || {
+            // For each thread, prepend a different number of declarations to the
+            // source code.
+            let mut prepend_line_count = 0;
+            let mut prepended_source = String::new();
+            for _ in 0..thread_id {
+                prepend_line_count += 2;
+                prepended_source += "struct X {}\n\n";
+            }
+
+            tree_clone.edit(&InputEdit {
+                start_byte: 0,
+                old_end_byte: 0,
+                new_end_byte: prepended_source.len(),
+                start_position: Point::new(0, 0),
+                old_end_position: Point::new(0, 0),
+                new_end_position: Point::new(prepend_line_count, 0),
+            });
+            prepended_source += this_file_source;
+
+            // Reparse using the old tree as a starting point.
+            let mut parser = Parser::new();
+            parser.set_language(rust()).unwrap();
+            parser
+                .parse_str(&prepended_source, Some(&tree_clone))
+                .unwrap()
+        }));
+    }
+
+    // Check that the trees have the expected relationship to one another.
+    let trees = parse_threads
+        .into_iter()
+        .map(|thread| thread.join().unwrap());
+    let child_count_differences = trees
+        .map(|t| t.root_node().child_count() - tree.root_node().child_count())
+        .collect::<Vec<_>>();
+
+    assert_eq!(child_count_differences, &[1, 2, 3, 4]);
+}
diff --git a/lib/binding/lib.rs b/lib/binding/lib.rs
index 88cc24be..08f863f8 100644
--- a/lib/binding/lib.rs
+++ b/lib/binding/lib.rs
@@ -94,7 +94,7 @@ pub struct PropertyTransitionJSON {
 
 #[derive(Debug, Deserialize, Serialize, PartialEq, Eq)]
 pub struct PropertyStateJSON {
-    pub id: usize,
+    pub id: Option<usize>,
     pub property_set_id: usize,
     pub transitions: Vec<PropertyTransitionJSON>,
     pub default_next_state_id: usize,
@@ -847,520 +847,3 @@ impl<P> PropertySheet<P> {
         })
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use std::thread;
-
-    fn rust() -> Language {
-        unsafe { tree_sitter_rust() }
-    }
-    extern "C" {
-        fn tree_sitter_rust() -> Language;
-    }
-
-    #[test]
-    fn test_basic_parsing() {
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-
-        let tree = parser
-            .parse_str(
-                "
-            struct Stuff {}
-            fn main() {}
-        ",
-                None,
-            )
-            .unwrap();
-
-        let root_node = tree.root_node();
-        assert_eq!(root_node.kind(), "source_file");
-
-        assert_eq!(
-            root_node.to_sexp(),
-            "(source_file (struct_item (type_identifier) (field_declaration_list)) (function_item (identifier) (parameters) (block)))"
-        );
-
-        let struct_node = root_node.child(0).unwrap();
-        assert_eq!(struct_node.kind(), "struct_item");
-    }
-
-    #[test]
-    fn test_logging() {
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-
-        let mut messages = Vec::new();
-        parser.set_logger(Some(Box::new(|log_type, message| {
-            messages.push((log_type, message.to_string()));
-        })));
-
-        parser
-            .parse_str(
-                "
-            struct Stuff {}
-            fn main() {}
-        ",
-                None,
-            )
-            .unwrap();
-
-        assert!(messages.contains(&(
-            LogType::Parse,
-            "reduce sym:struct_item, child_count:3".to_string()
-        )));
-        assert!(messages.contains(&(LogType::Lex, "skip character:' '".to_string())));
-    }
-
-    #[test]
-    fn test_tree_cursor() {
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-
-        let tree = parser
-            .parse_str(
-                "
-                    struct Stuff {
-                        a: A;
-                        b: Option<B>,
-                    }
-                ",
-                None,
-            )
-            .unwrap();
-
-        let mut cursor = tree.walk();
-        assert_eq!(cursor.node().kind(), "source_file");
-
-        assert!(cursor.goto_first_child());
-        assert_eq!(cursor.node().kind(), "struct_item");
-
-        assert!(cursor.goto_first_child());
-        assert_eq!(cursor.node().kind(), "struct");
-        assert_eq!(cursor.node().is_named(), false);
-
-        assert!(cursor.goto_next_sibling());
-        assert_eq!(cursor.node().kind(), "type_identifier");
-        assert_eq!(cursor.node().is_named(), true);
-
-        assert!(cursor.goto_next_sibling());
-        assert_eq!(cursor.node().kind(), "field_declaration_list");
-        assert_eq!(cursor.node().is_named(), true);
-    }
-
-    #[test]
-    fn test_tree_property_matching() {
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-        let source_code = "fn f1() { f2(); }";
-        let tree = parser.parse_str(source_code, None).unwrap();
-
-        #[derive(Debug, Deserialize, PartialEq, Eq)]
-        struct Properties {
-            reference: Option<String>,
-            define: Option<String>,
-        }
-
-        let empty_properties = Properties {
-            reference: None,
-            define: None,
-        };
-
-        let property_sheet = PropertySheet::<Properties>::new(
-            rust(),
-            r##"
-            {
-                "states": [
-                    {
-                        "transitions": [
-                            {"type": "call_expression", "named": true, "state_id": 1},
-                            {"type": "function_item", "named": true, "state_id": 2}
-                        ],
-                        "default_next_state_id": 0,
-                        "property_set_id": 0
-                    },
-                    {
-                        "transitions": [
-                            {"type": "identifier", "named": true, "state_id": 3}
-                        ],
-                        "default_next_state_id": 0,
-                        "property_set_id": 0
-                    },
-                    {
-                        "transitions": [
-                            {"type": "identifier", "named": true, "state_id": 4}
-                        ],
-                        "default_next_state_id": 0,
-                        "property_set_id": 0
-                    },
-                    {
-                        "transitions": [],
-                        "default_next_state_id": 0,
-                        "property_set_id": 1
-                    },
-                    {
-                        "transitions": [],
-                        "default_next_state_id": 0,
-                        "property_set_id": 2
-                    }
-                ],
-                "property_sets": [
-                    {},
-                    {"reference": "function"},
-                    {"define": "function"}
-                ]
-            }
-        "##,
-        )
-        .unwrap();
-
-        let mut cursor = tree.walk_with_properties(&property_sheet, source_code);
-        assert_eq!(cursor.node().kind(), "source_file");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-
-        assert!(cursor.goto_first_child());
-        assert_eq!(cursor.node().kind(), "function_item");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-
-        assert!(cursor.goto_first_child());
-        assert_eq!(cursor.node().kind(), "fn");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-        assert!(!cursor.goto_first_child());
-
-        assert!(cursor.goto_next_sibling());
-        assert_eq!(cursor.node().kind(), "identifier");
-        assert_eq!(cursor.node_properties().define, Some("function".to_owned()));
-        assert!(!cursor.goto_first_child());
-
-        assert!(cursor.goto_next_sibling());
-        assert_eq!(cursor.node().kind(), "parameters");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-
-        assert!(cursor.goto_first_child());
-        assert_eq!(cursor.node().kind(), "(");
-        assert!(cursor.goto_next_sibling());
-        assert_eq!(cursor.node().kind(), ")");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-
-        assert!(cursor.goto_parent());
-        assert!(cursor.goto_next_sibling());
-        assert_eq!(cursor.node().kind(), "block");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-
-        assert!(cursor.goto_first_child());
-        assert!(cursor.goto_next_sibling());
-        assert_eq!(cursor.node().kind(), "call_expression");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-
-        assert!(cursor.goto_first_child());
-        assert_eq!(cursor.node().kind(), "identifier");
-        assert_eq!(
-            cursor.node_properties().reference,
-            Some("function".to_owned())
-        );
-    }
-
-    #[test]
-    fn test_tree_property_matching_with_regexes() {
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-        let source_code = "fn f1() { None(a()) }";
-        let tree = parser.parse_str(source_code, None).unwrap();
-
-        #[derive(Debug, Deserialize, PartialEq, Eq)]
-        struct Properties {
-            scope: Option<String>,
-        }
-
-        let empty_properties = Properties { scope: None };
-
-        let property_sheet = PropertySheet::<Properties>::new(
-            rust(),
-            r##"
-            {
-                "states": [
-                    {
-                        "id": 0,
-                        "transitions": [
-                            {"type": "call_expression", "named": true, "state_id": 1}
-                        ],
-                        "default_next_state_id": 0,
-                        "property_set_id": 0
-                    },
-                    {
-                        "id": 1,
-                        "transitions": [
-                            {"type": "identifier", "named": true, "text": "^[A-Z]", "state_id": 2},
-                            {"type": "identifier", "named": true, "state_id": 3}
-                        ],
-                        "default_next_state_id": 0,
-                        "property_set_id": 0
-                    },
-                    {
-                        "transitions": [],
-                        "default_next_state_id": 0,
-                        "property_set_id": 1
-                    },
-                    {
-                        "transitions": [],
-                        "default_next_state_id": 0,
-                        "property_set_id": 2
-                    }
-                ],
-                "property_sets": [
-                    {},
-                    {"scope": "constructor"},
-                    {"scope": "function"}
-                ]
-            }
-        "##,
-        )
-        .unwrap();
-
-        let mut cursor = tree.walk_with_properties(&property_sheet, source_code);
-        assert_eq!(cursor.node().kind(), "source_file");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-
-        cursor.goto_first_child();
-        assert!(cursor.goto_first_child());
-        assert!(cursor.goto_next_sibling());
-        assert!(cursor.goto_next_sibling());
-        assert!(cursor.goto_next_sibling());
-        assert_eq!(cursor.node().kind(), "block");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-
-        assert!(cursor.goto_first_child());
-        assert!(cursor.goto_next_sibling());
-        assert_eq!(cursor.node().kind(), "call_expression");
-        assert_eq!(*cursor.node_properties(), empty_properties);
-
-        assert!(cursor.goto_first_child());
-        assert_eq!(cursor.node().kind(), "identifier");
-        assert_eq!(
-            cursor.node_properties().scope,
-            Some("constructor".to_owned())
-        );
-    }
-
-    #[test]
-    fn test_custom_utf8_input() {
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-
-        let lines = &["pub fn foo() {", "  1", "}"];
-
-        let tree = parser
-            .parse_utf8(
-                &mut |_, position| {
-                    let row = position.row;
-                    let column = position.column;
-                    if row < lines.len() {
-                        if column < lines[row].as_bytes().len() {
-                            &lines[row].as_bytes()[column..]
-                        } else {
-                            "\n".as_bytes()
-                        }
-                    } else {
-                        &[]
-                    }
-                },
-                None,
-            )
-            .unwrap();
-
-        let root = tree.root_node();
-        assert_eq!(root.to_sexp(), "(source_file (function_item (visibility_modifier) (identifier) (parameters) (block (integer_literal))))");
-        assert_eq!(root.kind(), "source_file");
-        assert_eq!(root.has_error(), false);
-        assert_eq!(root.child(0).unwrap().kind(), "function_item");
-    }
-
-    #[test]
-    fn test_custom_utf16_input() {
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-
-        parser.set_logger(Some(Box::new(|t, message| {
-            println!("log: {:?} {}", t, message);
-        })));
-
-        let lines: Vec<Vec<u16>> = ["pub fn foo() {", "  1", "}"]
-            .iter()
-            .map(|s| s.encode_utf16().collect())
-            .collect();
-
-        let tree = parser
-            .parse_utf16(
-                &mut |_, position| {
-                    let row = position.row;
-                    let column = position.column;
-                    if row < lines.len() {
-                        if column < lines[row].len() {
-                            &lines[row][column..]
-                        } else {
-                            &[10]
-                        }
-                    } else {
-                        &[]
-                    }
-                },
-                None,
-            )
-            .unwrap();
-
-        let root = tree.root_node();
-        assert_eq!(root.to_sexp(), "(source_file (function_item (visibility_modifier) (identifier) (parameters) (block (integer_literal))))");
-        assert_eq!(root.kind(), "source_file");
-        assert_eq!(root.has_error(), false);
-        assert_eq!(root.child(0).unwrap().kind(), "function_item");
-    }
-
-    #[test]
-    fn test_node_equality() {
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-        let tree = parser.parse_str("struct A {}", None).unwrap();
-        let node1 = tree.root_node();
-        let node2 = tree.root_node();
-        assert_eq!(node1, node2);
-        assert_eq!(node1.child(0).unwrap(), node2.child(0).unwrap());
-        assert_ne!(node1.child(0).unwrap(), node2);
-    }
-
-    #[test]
-    fn test_editing() {
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-
-        let mut input_bytes = "fn test(a: A, c: C) {}".as_bytes();
-        let mut input_bytes_read = Vec::new();
-
-        let mut tree = parser
-            .parse_utf8(
-                &mut |offset, _| {
-                    let offset = offset;
-                    if offset < input_bytes.len() {
-                        let result = &input_bytes[offset..offset + 1];
-                        input_bytes_read.extend(result.iter());
-                        result
-                    } else {
-                        &[]
-                    }
-                },
-                None,
-            )
-            .unwrap();
-
-        let parameters_sexp = tree
-            .root_node()
-            .named_child(0)
-            .unwrap()
-            .named_child(1)
-            .unwrap()
-            .to_sexp();
-        assert_eq!(
-            parameters_sexp,
-            "(parameters (parameter (identifier) (type_identifier)) (parameter (identifier) (type_identifier)))"
-        );
-
-        input_bytes_read.clear();
-        input_bytes = "fn test(a: A, b: B, c: C) {}".as_bytes();
-        tree.edit(&InputEdit {
-            start_byte: 14,
-            old_end_byte: 14,
-            new_end_byte: 20,
-            start_position: Point::new(0, 14),
-            old_end_position: Point::new(0, 14),
-            new_end_position: Point::new(0, 20),
-        });
-
-        let tree = parser
-            .parse_utf8(
-                &mut |offset, _| {
-                    let offset = offset;
-                    if offset < input_bytes.len() {
-                        let result = &input_bytes[offset..offset + 1];
-                        input_bytes_read.extend(result.iter());
-                        result
-                    } else {
-                        &[]
-                    }
-                },
-                Some(&tree),
-            )
-            .unwrap();
-
-        let parameters_sexp = tree
-            .root_node()
-            .named_child(0)
-            .unwrap()
-            .named_child(1)
-            .unwrap()
-            .to_sexp();
-        assert_eq!(
-            parameters_sexp,
-            "(parameters (parameter (identifier) (type_identifier)) (parameter (identifier) (type_identifier)) (parameter (identifier) (type_identifier)))"
-        );
-
-        let retokenized_content = String::from_utf8(input_bytes_read).unwrap();
-        assert!(retokenized_content.contains("b: B"));
-        assert!(!retokenized_content.contains("a: A"));
-        assert!(!retokenized_content.contains("c: C"));
-        assert!(!retokenized_content.contains("{}"));
-    }
-
-    #[test]
-    fn test_parallel_parsing() {
-        // Parse this source file so that each thread has a non-trivial amount of
-        // work to do.
-        let this_file_source = include_str!("lib.rs");
-
-        let mut parser = Parser::new();
-        parser.set_language(rust()).unwrap();
-        let tree = parser.parse_str(this_file_source, None).unwrap();
-
-        let mut parse_threads = Vec::new();
-        for thread_id in 1..5 {
-            let mut tree_clone = tree.clone();
-            parse_threads.push(thread::spawn(move || {
-                // For each thread, prepend a different number of declarations to the
-                // source code.
-                let mut prepend_line_count = 0;
-                let mut prepended_source = String::new();
-                for _ in 0..thread_id {
-                    prepend_line_count += 2;
-                    prepended_source += "struct X {}\n\n";
-                }
-
-                tree_clone.edit(&InputEdit {
-                    start_byte: 0,
-                    old_end_byte: 0,
-                    new_end_byte: prepended_source.len(),
-                    start_position: Point::new(0, 0),
-                    old_end_position: Point::new(0, 0),
-                    new_end_position: Point::new(prepend_line_count, 0),
-                });
-                prepended_source += this_file_source;
-
-                // Reparse using the old tree as a starting point.
-                let mut parser = Parser::new();
-                parser.set_language(rust()).unwrap();
-                parser
-                    .parse_str(&prepended_source, Some(&tree_clone))
-                    .unwrap()
-            }));
-        }
-
-        // Check that the trees have the expected relationship to one another.
-        let trees = parse_threads
-            .into_iter()
-            .map(|thread| thread.join().unwrap());
-        let child_count_differences = trees
-            .map(|t| t.root_node().child_count() - tree.root_node().child_count())
-            .collect::<Vec<_>>();
-
-        assert_eq!(child_count_differences, &[1, 2, 3, 4]);
-    }
-}
diff --git a/lib/build.rs b/lib/build.rs
index f8c19f05..7e8714ef 100644
--- a/lib/build.rs
+++ b/lib/build.rs
@@ -46,6 +46,7 @@ fn main() {
             println!("cargo:rerun-if-changed={}", parser_c_path.to_str().unwrap());
             parser_config
                 .include(&parser_src_path)
+                .opt_level(0)
                 .file(&parser_c_path);
             if scanner_cc_path.exists() {
                 println!("cargo:rerun-if-changed={}", scanner_cc_path.to_str().unwrap());