diff --git a/lang/src/tokeniser.asm b/lang/src/tokeniser.asm
index 92a6a18..a5e548f 100644
--- a/lang/src/tokeniser.asm
+++ b/lang/src/tokeniser.asm
@@ -21,6 +21,8 @@ extern is_whitespace
 global tokeniser_init
 global tokeniser_print
 global find_lexeme
+global expect_token
+global unwrap_token
 
 ;; =============================
 ;; Tokeniser functions
@@ -702,3 +704,42 @@ find_lexeme:
     mov qword [rdi], TOKEN_COMMENT
     mov [rdi + 16], rax
     jmp .epilogue
+
+;; dil: expected token
+expect_token:
+    push rbp
+    mov rbp, rsp
+    sub rsp, 0x30
+    mov [rsp], dil
+    mov rax, [rel cursor]       ; current cursor
+    mov [rsp + 8], rax
+    lea rdi, [rsp + 0x10]
+    call find_lexeme
+    mov rax, [rsp + 0x10]    ; found token
+    mov dil, [rsp]          ; expected token
+    cmp al, dil
+    je .matched
+    mov rdi, [rsp + 8]     ; restore cursor
+    mov [rel cursor], rdi    ; restore cursor
+    xor rax, rax
+    xor rdx, rdx
+    jmp .epilogue
+.matched:
+    mov rax, [rsp + 0x18]   ; lexeme pointer
+    mov rdx, [rsp + 0x20]   ; lexeme length
+.epilogue:
+    add rsp, 0x30
+    pop rbp
+    ret
+
+;; dil: expected token
+unwrap_token:
+    push rbp
+    mov rbp, rsp
+    call expect_token
+    test rax, rax
+    jz .panic
+    pop rbp
+    ret
+.panic:
+    call panic
diff --git a/lang/tests/bump.rs b/lang/tests/bump.rs
index db39ffc..ca57ddf 100644
--- a/lang/tests/bump.rs
+++ b/lang/tests/bump.rs
@@ -1,9 +1,7 @@
 #![feature(allocator_api, box_as_ptr)]
 
-#[unsafe(no_mangle)]
-extern "C" fn panic() -> ! {
-    panic!("Called panic from external code.");
-}
+#[path = "shared/shared.rs"]
+mod util;
 
 unsafe extern "C" {
     unsafe fn bump_init();
diff --git a/lang/tests/int_to_str.rs b/lang/tests/int_to_str.rs
index 87db35f..20f66a5 100644
--- a/lang/tests/int_to_str.rs
+++ b/lang/tests/int_to_str.rs
@@ -1,22 +1,7 @@
-#[unsafe(no_mangle)]
-extern "C" fn panic() -> ! {
-    panic!("Called panic from external code.");
-}
+#[path = "shared/shared.rs"]
+mod util;
 
-#[repr(C)]
-struct FFISlice {
-    ptr: *const u8,
-    len: usize,
-}
-
-impl FFISlice {
-    fn as_slice(&self) -> &[u8] {
-        unsafe { core::slice::from_raw_parts(self.ptr, self.len) }
-    }
-    fn as_str(&self) -> &str {
-        unsafe { core::str::from_utf8_unchecked(self.as_slice()) }
-    }
-}
+use util::FFISlice;
 
 unsafe extern "C" {
     unsafe fn int_to_str2(value: isize, buffer: *mut u8, buffer_len: usize, radix: u8) -> FFISlice;
diff --git a/lang/tests/shared/shared.rs b/lang/tests/shared/shared.rs
new file mode 100644
index 0000000..ce87f4c
--- /dev/null
+++ b/lang/tests/shared/shared.rs
@@ -0,0 +1,40 @@
+#[unsafe(no_mangle)]
+extern "C" fn panic() -> ! {
+    panic!("Called panic from external code.");
+}
+
+#[repr(C)]
+#[derive(Debug, PartialEq, Eq)]
+pub struct FFISlice {
+    pub ptr: *const u8,
+    pub len: usize,
+}
+
+#[repr(transparent)]
+#[derive(Debug, PartialEq, Eq)]
+pub struct MaybeFFISlice {
+    inner: FFISlice,
+}
+
+impl MaybeFFISlice {
+    pub fn is_none(&self) -> bool {
+        self.inner.ptr.is_null()
+    }
+
+    pub fn into_option(self) -> Option<FFISlice> {
+        if self.is_none() {
+            None
+        } else {
+            Some(self.inner)
+        }
+    }
+}
+
+impl FFISlice {
+    pub fn as_slice(&self) -> &[u8] {
+        unsafe { core::slice::from_raw_parts(self.ptr, self.len) }
+    }
+    pub fn as_str(&self) -> &str {
+        unsafe { core::str::from_utf8_unchecked(self.as_slice()) }
+    }
+}
diff --git a/lang/tests/tokens.rs b/lang/tests/tokens.rs
index 72ffb4c..8c594cb 100644
--- a/lang/tests/tokens.rs
+++ b/lang/tests/tokens.rs
@@ -1,7 +1,7 @@
-#[unsafe(no_mangle)]
-extern "C" fn panic() -> ! {
-    panic!("Called panic from external code.");
-}
+#[path = "shared/shared.rs"]
+mod util;
+
+use util::*;
 
 #[derive(Debug)]
 struct Lexeme(u8, &'static str);
@@ -55,6 +55,8 @@ unsafe extern "C" {
     unsafe fn skip_whitespace() -> ();
 
     unsafe fn find_lexeme() -> LexemeRaw;
+    unsafe fn expect_token(token: u8) -> MaybeFFISlice;
+    unsafe fn unwrap_token(token: u8) -> FFISlice;
 
     static mut LEXEMES: *const u8;
     static mut LEXEME_LENS: usize;
@@ -171,6 +173,14 @@ fn main() {
             ]
         );
 
+        eprint!("Initializing tokeniser.. ");
+        tokeniser_init(c"tests/tokens/function.l".as_ptr());
+        eprintln!("ok.");
+
+        assert_eq!(expect_token(2).into_option(), None);
+        assert_eq!(expect_token(4).into_option().unwrap().as_str(), "fn");
+        assert_eq!(unwrap_token(30).as_str(), "my-function");
+
         eprint!("Initializing tokeniser.. ");
         tokeniser_init(c"tests/tokens/comment.l".as_ptr());
         eprintln!("ok.");